Aculeata Agonistes: Bombus Squared & Gone?

Herein, I begin my bumbling through the subgenera and species of Bombus in the Edmonton area with what seemed like an easy start: Bombus (Bombus). Thanks to the online resources that Paul Williams has created at the British Museum of Natural History website, I know that only 11 of the 250 or so recognized species of bumble bee belong to the nominate subgenus – less than 5%. Also, selecting the Nearctic Region from the key, I can reduce this to 4 possible species, albeit with 21 different colour forms. However, according to Richards (1978 – see citations at end) Alberta is abuzz with 21 species of Bombus – how can I tell if any of my bees are Bombus (Bombus)?

The best solution would be to ask a specialist on Bombus and preferably one with knowledge of the local fauna. Alas, no one I know will admit to such knowledge. I could try Calgary – there are bumble bee ecologist there - but here the response from the hymenopterists here has been to bugger off and learn them myself, they have more than enough to do already (which is probably what the Calgary ecologists would say). This is called a ‘taxonomic impediment’ (TI) – a well-known problem to overworked taxonomists and frustrated people who need identifications, but seemingly of limited interest to most of the world. For example, Google comes up with less than 60 thousand hits for ‘taxonomic impediment’, but 27 times as many (1,610,000) for ‘bee decline’.

For those who haven’t heard of TI before, here’s a definition from an Australian source that is more than 15 years old: “The taxonomic impediment to progress in the study of biodiversity is linked to a worldwide shortage of taxonomists who can be called upon to identify species, describe species that are new to science, determine their taxonomic relationships, and make predictions about their properties.” And, 15 years later, if you are interested in how Canada is dealing with TI, then you are in luck: last week the Council of Canadian Academies released Canadian Taxonomy: Exploring Biodiversity, Creating Opportunity. You can download the 4mb pdf for free – but to make a long story short: “Job openings in taxonomy have virtually ceased’ … ‘Canada’s ranking [in taxonomic publications] dropped from 6th in the 1980s to 14th in the 2000s’ ... [and most relevant to this post] ‘pollinators provide a crucial ecosystem service (via fertilization of crops) to agriculture, yet there is a growing taxonomic expertise gap in pollinator identification.”

Okay, I get the point – the Government may tut-tut about the shortage of taxonomists every decade or two, but better look elsewhere for a solution. Is there a generous specialist from some more enlightened elsewhere with a pro bono bombology streak? Well, one could submit pictures to BugGuide where John Ascher seems to have the talent to name that bee. For example, The Bugwhisperer’s recent spectacular photo of a Bombus melanopygus ménage à trios now resides name and all on BugGuide. The BugGuide route is tempting, but Dr Ascher probably has more than enough to do as it is. In theory, I have some skill with arthropods, small though it may be, and it’s not like I’ll be seeing any new bumble bees before May. If I could make a small, local contribution to the pollinator expertise gap, then it would be a pleasant break from shoveling snow.

So, what lies ahead? Richards (1978) reported that 15 species of Bombus could be found in Aspen Parkland in southwest Alberta. That is a pretty good diversity considering that Donovall & van Engelsdorp (2010) found records for only 17 species of Bombus in the entire state of Pennsylvania and Grixti et al. (2009) only 16 for Illinois (and four of these appear to be locally extinct). I don’t know if a similar diversity survives in the lower elevation (~700 m) former Aspen Parkland of the Home Bug Garden, but this is mostly because we HBGs have been loathe to collect and kill. Instead, we flutter around flowers with our cameras capturing many a mysterious mugshot. I’ve spent much of my spare time the last few weeks perusing BugGuide for matches, but I’ll be buggered if I can identify many pictures with any certainty. That leaves the Laverty & Harder, Discover Life, and BMNH keys (see previous post for links). The authors of these keys, however, expect you to know all the characters they think important, not just those you happen to have photographed clearly.

The keys also are written with the expectation that you to have a bumble bee in hand, and not some faker. Discover Life does have a Bumblebees & Mimics Key with some of the likely mistakes. Robber flies (Diptera, Asilidae, Laphria spp.) and hover flies (Syrphidae) such as Volucella bombylans are the mimics with the mostest – but as with the drone flies discussed in the previous post, the wings, head, and antennae give away their true fly identity. Also, any ‘bumblebee’ eating another insect is not a Bombus. If you live further south, you could be fooled by large carpenter bees in the genus Xylocopa especially the Eastern Carpenter Bee X. virginica, but they do not make their homes in Alberta. We do, however, have several bumblebeeish solitary bees, e.g. some digger bees (Andrena) and mason bees (Osmia). All I can say is that most bees do not resemble Bombus except in the most bee-general way, and those that do are only as large as the smallest bumble bee workers, their fur isn’t as brightly coloured, and they never have orange bands (but a red thorax is possible).

Bumble bees themselves indulge in mimicking each other which leads to convergence in colour patterns between species: mimicry complexes that emphasize the “don’t mess with me” message of the boldly contrasting bands of black and brightly coloured hairs (the skin itself is invariably black). Self-mimicry is probably the primary non-taxonomic impediment to bumble bee identification. So, if one wants to pursue the species identity of the local Bombus, you need to take one of two routes: (1) collect, kill, and pin a good selection or (2) take lots of photographs of individuals from every angle. If one really wants to get serious about Bombus identity, then you need to consider being even more intrusive than the TSA and pulling out the genitalia of the males for inspection. Male claspers are a useful guide to Bombus subgenera and probably to species. Williams at the BMNH provides a rather Andy Warholish gallery of dissected male claspers. I’m sure this is a worthy project, but at my level of understanding, I can’t say that the images are of much help. However, the Home Bug Garden has now become a dangerous place for lazy, shiftless drone bumble bees (the corpses of whom are destined to repose in the Royal Alberta Museum – where irrespective any names I rightly or wrongly put on them, they will contribute to a record of what lived here at this time).

So on to our first subgenus Bombus (Bombus) – a mere 11 species worldwide and only 4 in the Nearctic. Range and unique colour patterns can be used to eliminate three of the four species from my female Bombus. That leaves Bombus (Bombus) terricola looking like some of my bees. A good colour pattern character is that the upper side (tergum) of first and fourth segments (T1 and T4) of the ‘abdomen*’ are covered in black hairs and the second and third (T2, 3) with yellow hairs (remember the skin underneath is black). This contrasting yellow-black pattern, I suppose, accounts for the common name Yellow-banded Bumble Bee. No other local Bombus have this specific pattern, although many are black and yellow. The only local Bombus with the first abdominal segment black belong to the subgenus Psithyrus – cuckoo bees that usurp young colonies of species in other subgenera of Bombus – and these kleptoparasites also have black-haired second abdominal terga.

Among those bees pinned and pictured are a few with a black-yellow-yellow-black abdominal pattern and also a yellow-black thorax and other characters consistent in all three keys = Yellow-banded Bumble Bee Bombus terricola. One of my pinned specimens is a TSA’d male and the genitalia match the BMNH picture. However, on double checking for somewhere I may have gone wrong, I found a species on BugGuide - Bombus occidentalis – that is not present in the Williams’ key. A little searching on other pages of the website discloses that current research suggests that occidentalis and terricola may be one highly variable species, which helps explain the 13 different colour form pictures in the Williams’ key for terricola. This would be a bit annoying if I had colour morphs attributable to occidentalis (especially since Bertsch et al. 2010 think they are both good species) but I don’t. The reason that I don’t is probably because (a) occidentalis was restricted to southern Alberta (Hobbs 1968) and (b) this once common species has essentially disappeared in the last two decades (Evans et al. 2008).

Now that we have an id, what can we say about our bee? Well, Laverty & Harder (1988) list it as an underground nester (places like rodent burrows are good) and with early spring emerging queens. Like all bumble bees, Bombus (Bombus) terricola is considered a long-tongued bee, but all is relative: our humble bee is rather short-tongued. This means that terricola can pollinate only relatively shallow flowers or those that require buzz pollination. But as Laverty & Harder point out “queens and workers commonly bite holes in flowers with long corolla tubes”. Technically, this makes terricola a nectar robber and not necessarily the best pollinator in an ecosystem. Also, terricola seems to be a bit lazy when it comes to foraging from shallow flowers – it prefers to walk when it can, rather than fly.

Plowright & Plowright (1998) noticed that at a site in Ontario where B. terricola and B. ternarius (one of the orange banded bees in the subgenus Pyrobombus) were foraging at the same time, terricola was confined to the milkweed Asclepias syriaca L. – a plant with a dense cluster of upright flowers – and ternarius to the dogbane Apocynum androsaemifoliurn L. – a plant with loose clusters of pendulant flowers. At another site without milkweed, however, both species foraged together in dense patches of dogbane. Their observations and experiments demonstrated that B. terricola is relatively inefficient at flying between flowers, and so tends to visit dogbane only in areas where the plants are dense and closely spaced. Also, Williams et al. (2008) note that Pyrobombus species are noted for their ability to forage from hanging flowers, no doubt giving them an advantage when there is no easier alternative.

All this is interesting, but the place that B. terricola most often shows up in studies is where it isn’t showing up at all – this is one of the species that appears to be disappearing. What could account for the decline? Perhaps as a consequence of emerging early in the spring, Franklin & Sampson (1992) report that the cuckoo bee Bombus (Psithyrus) ashtoni will usurp terricola nests. Cuckoo bees enter a young nest, usually kill the resident queen, and then take over the workers to raise new queen and drone cuckoos. B. (P.) ashtoni, however, is also in decline and may be on the edge of extinction (Evans et al. 2008), presumably because of the decline of its hosts B. (B.) terricola and the related B. (B.) affinis.

Well, if not a cuckoo, then perhaps a predator is knocking off our B. terricola. There are lots of predators and parasites of bumble bees and Morse & Myles (2005) found that B. terricola workers showed no tendency to avoid patches of milkweed with predatory crab spiders. However, mice, shrews, ants, parasitic conopid and syrphid flies, crab spiders, and ambush bugs seem to be problems with which all Bombus must deal, so too the habitat destruction and pesticide encounters that are the suspected causes of much native bee decline. A more insidious cause, and one that seems a likely explanation for the rapid decline of the species in the subgenus Bombus is pathogen spillover (Colla et al. 2006, Rao & Stephen 2007, Otterstatter & Thomson. 2008).

Members of the subgenus Bombus are good pollinators, including of plants that require buzz pollination, and these bees are easy to rear and handle. As a result, Bombus (Bombus) species such as the European terrestris and the North American occidentalis have been mass reared and shipped around the World. As part of these commercial operations, New World bees have been exposed to Old World pathogens and then shipped back to North America for use in greenhouses. Invariably, some escape and intermingle with native bees foraging at flowers around greenhouse facilities. The result is the spread of Old World diseases for which our New World bees have little or no resistance. What a bummer: the first bumble bee that I feel comfortable identifying is now on its way to the Red List of Threatened Species (Mann 2010). I guess I can take some comfort in knowing that, although rare, they are still here around Edmonton. Perhaps some of these survivors are resistant to the introduced diseases and with luck the populations will eventually recover.

*All aculeate Hymenoptera have a ‘wasp-waist’ or petiole that divides the first segment of the abdomen from the remainder. Although there are technical terms for this reorganization of the abdomen, aculeate workers seem happy to use abdomen for the rump and start numbering with the first apparent segment, and so shall I.


Literature Cited

Bertsch A, de Angelis MH & Przemeck GKH. 2010. A phylogenetic framework for the North American bumblebee species of the subgenus Bombus sensu stricto (Bombus affinis, B. franklini, B. moderatus, B. occidentalis & B. terricola) based on mitochondrial DNA markers (Hymenoptera: Apidae: Bombus). Beitraege zur Entomologie 60: 229-242.

Colla SR & Packer L. 2008. Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson. Biodiversity and Conservation 17: 1379-1391.

Colla SR, Otterstatter MC, Gegear RJ & Thomson JD. 2006. Plight of the bumble bee: Pathogen spillover from commercial to wild populations. Biological Conservation 129: 461-7.

Donovall LR & van Engelsdorp D. 2010. A Checklist of the Bees (Hymenoptera: Apoidea) of Pennsylvania. J Kansas Ent Soc 83: 7–24.

Evans E, Thorp R, Jepsen S & S. Black H. 2008. Status Review of Three Formerly Common Species of Bumble Bee in the Subgenus Bombus. Prepared for the Xerces Society of Invertebrate Conservation [Online]:
http://www.xerces.org/wpcontent/uploads/2008/12/xerces_2008_bombus_status_review.pdf

Grixti J C, Wonga LT, Cameron SA, & Favret C. 2009. Decline of bumble bees (Bombus) in the North American Midwest. Biol Conserv 142: 75-84)

Fisher RM & Sampson BJ. 1992. Morphological specializations of the bumble bee social parasite Psithyrus ashtoni (Cresson) (Hymenoptera: Apidae). Can. Ent. 124: 69-77.

Hobbs GA. 1968. Ecology of species of Bombus Latr. (Hymenoptera: Apidae) in southern Alberta. VI. Subgenus Bombus, Canadian Entomologist 100: 156-164.

Laverty TM. & LD Harder. 1988. The bumble bees of eastern Canada. The Canadian Entomologist 120: 965-987.

Mann A. 2010. Plight of the bumblebee. Nature News. http://www.nature.com/news/2010/101117/full/news.2010.614.html?WT.ec_id=NEWS-20101123

Otterstatter M C & J D Thomson. 2008. Does pathogen spillover from commercially reared bumble bees threaten wild pollinators? PLoS ONE 3(7):e2771.

Plowright, CMS & Plowright, R.C. 1998. Floral use by two sympatric bumble bee species (Bombus terricola and Bombus ternarius): efficiency considerations. Canadian Entomologist 130: 595 – 601.

Richards KW. 1978. Nest site selection by bumble bees (Hymenoptera: Apidae)in southern Alberta. Can. Ent. 110: 301-318.

Rao S & Stephen WP. 2007. Bombus (Bombus) occidentalis (Hymenoptera: Apiformes): In decline or recovery? The Pan-Pacific Entomologist 83:360–362.

Williams PH, Cameron SA, Hines HM, Cederberg B & Rasmont P. 2008. A simplified subgeneric classification of the bumblebees (sic) (genus Bombus). Apidologies 39: 1-29.

Aculeata Agonistes: Bumbling among the Bombus

 Although a few flowers are still defrosting on sunny days, it has been several weeks since the last greedily feeding queen bumblebee has been active. Or rather, I should say ‘bumble bee’ not ‘bumblebee’, because I don’t want to upset any entomologists. Bug people have a simple rule about names with a bug in them: if the common name is technically correct, then keep them separate; if not, merge them. Hence the dragonflies and damselflies in the last post are merged. They are not true flies (= Diptera), but bumble bees and honey bees are true bees (= Apoidea), so keep them separate.

 I admit that I’m not always properly pedantic about bees (bumblebee has ruled on this blog) and sometimes it can get perplexing. For example, what to do about a ‘bee fly’: a fly true, but a bee not. I guess the noun used as a noun trumps the noun used as an adjective, so bee fly it is. Then there is the ‘fly bee’ that adorns Small Farm Canada’s otherwise exemplary editorial “Bee-ware” (Nov-Dec 2010, p. 13 in hard copy) about the importance of bees as pollinators and their apparent decline in abundance. Unfortunately, the picture of a bee in a pasture is actually a hover fly, probably the Drone Fly (Eristalis tenax), a mimic of honey bees. A mistake like this really bugs entomologists, but probably makes life easier for the fly.

 Technically, calling a fly a bee is a big time taxonomic failure that you can quantify if you’d like using the Myrmecos Taxonomy Fail Index. Perhaps more importantly, if you can’t tell a hover fly from a bee, then you may not notice if your bees start disappearing. Many flies are pollinators, especially of easily accessed flowers like daisies or apples, but in general bees are what you want to see visiting flowers, at least if you want to maximize your production. Also, many structurally complex flowers require bees for pollination. For example those interesting pea-like flowers that adorn legumes (e.g. alfalfa, clover, peas, beans, lentils, peanuts) usually need a bee that knows how to pry apart the petals to get at the goodies. Then there are those crops with specialized anthers that require buzz-pollination (e.g. tomato, egg plant, blueberries). Nature is full of strange pollination syndromes and bees are integral to many. Even seemingly simple flowers, e.g. those of squash, have bees that specialize on them.

 There are lots of different kinds of bees – perhaps 25,000 different species sharing the Earth with us at this very moment. That seems like a lot to keep track of and, in fact, fewer than 20 thousand have been given names and we know little about more than a few species. Foremost among these favoured few are the members of the genus Apis – barely more than a half dozen species. In much of the World it is one species, the honey bee (Apis mellifera), that we depend on for honey and pollination. Here and there in far parts of the World or here in specialized jobs (e.g. alfalfa bees) people have developed mutually beneficial relationships with other kinds of bees, but for the most part bees go about their business with more hindrance than help from us.

 How much we may be hindering wild bees is a question now being asked, but one that is difficult to answer. A recent study using museum specimens (Grixta et al. 2009. Biological Conservation 142: 75-84) came to the conclusion that half of the bumble bee (Bombus) species historically present in the state of Illinois had become locally extinct or highly reduced. Colla & Harder (2008, Biodivers Conserv 17:1379–1391) also found an apparent general decline in bumble bees in southern Ontario. These results would seem to mirror the declines and local extinctions of bumble bees that have been reported in Europe.

 So what is happening in the Edmonton area? To know whether a bee is doing well or is in decline, one must first be able to put a name on it. In my experience, most entomologists can tell a bee from a fly, and many can make a good guess at family or genus, but usually only those that have specialized on bees can make a good guess at the species identity. This is true even of large, colourful, and noisy bees like bumble bees. A bumble bee proclaims its genus to anyone who cares to look, but keeps its species identity closely guarded.

 So is it possible to identify the Home Bug Garden bumble bees to species – especially without killing them? Well there is a key, Laverty & Harder (1988)*, and it is worth quoting what they think: “The single most useful character for species identification is colour pattern.” (Can. Ent. 120: 966). Sounds like bumble bees and birds may have something in common. However, there is a caveat: “It should be noted that although colour pattern is usually a reliable guide to species, colour variants do occur and misidentification of some specimens is inevitable. We estimate that about 5% of specimens identified by the key will be incorrect... (p. 967).” Also, alas, the key is to the bumble bees of eastern Canada and does not include some of the most common ones in the Edmonton area. However, it does have black & white cartoon-like images of the colour patterns in the 26 species of Bombus covered in the key.

Discover Life also has a key to North American bumble bees. I’ve found this key to be a bit difficult to use and the answers I get don’t always match up to pictures (mostly really sad looking pinned specimens) or distributions (which seem to be more museum collection records than actual distributions). My getting a wrong answer may say more about me than the key, but I’m willing to share the blame. Also, the Discover Life key is clearly under construction and it seems to be improving all the time. For example, it now has Canadian Provinces as one of the characters that can be used to reduce the number of taxa.

Continuing with the Worldwide Web, perhaps the most definitive of all bumble bee keys is the British Museum of Natural History’s Paul Williams’ Lucid interactive key to queens and workers (males are not included) of the World. As with any image-rich interactive key, this requires a fast internet connection and a reasonably powerful computer to avoid giving up in frustration. The complete key contains 1070 diagrammatic images of various colour patterns, but one can select only those in the Nearctic Region – only 220 colour patterns! After that one must have some idea of the subgenus to have much hope of making progress. Subgenera should provide some grist for the Aculeate Agonistes mill and I think Bombus (Bombus) will be the first up – a nice simple, small subgenus. The colour pattern diagrams in Williams’ key and the early, black & white examples in Laverty & Harder seem pretty useful. I’m not much of an artist, but I can handle computer drawing programs and will try work up a key using cartoons and pictures to the Edmonton bumble bee fauna. Here’s a first start comparing two common black & yellow local bumble bees. Any not too caustic suggestions for improvement appreciated.

I'm sure I will be making lots of errors as I bumble through the Bombus. Corrections are always appreciated, but I hope I don't end up on Arthropoda Blog's Friday Fail!

*Laverty TM. & LD Harder. 1988. The bumble bees of eastern Canada. The Canadian Entomologist 120: 965-987.

Dragons & Damsels: Odonate Overlap

Although killing frosts struck on 17 September, a week before schedule, after this Summer, September was quite a pleasant month. October has been up and down, and not much greenery or insects are in evidence, but the pond bubbler is still on. I usually chicken out in the first or second week of October, but the pump has persevered for 5 summers and probably won’t last that much longer anyway. So, for the benefit of the resident ‘native’ birds (chickadees, red and white breasted nuthatches, house finches, blue jays, and magpies), I’ve kept it going. Soon, though, I will have to give in to the ice gods.

So, what better excuse on a cool, but sunny Saturday, to post about some aquatic insects – and also, to start answering a question that Middle Earth Garden asked back in March – just how similar is the Home Bug Garden fauna to other more natural systems in Alberta? Her question is actually far more interesting than I can attempt to answer. I’d love to spend my summers wandering Alberta and documenting the various insect faunas, but so far no one has offered me a job doing so. However, I do spend many of my weekends at our Moose Pasture and at least for certain groups, I can now make reasonable comparisons between the HBG and the MP. (NB – pictures with blue borders are from the Moose Pasture, no colour borders from the Home Bug Garden.)

 First up is the Odonata. Even the smallest adult odonates are relatively large (or at least long) insects, often very abundant, and not as leery of people as many others. Thus they are more obliging to the photographer and especially friendly for close-focusing binoculars (I like my Pentax UCF XII). BugGuide has many good pictures and even better, for Christmas I got an excellent guide: Dennis Paulson’s Dragonflies and Damselflies of the West (2009, Princeton University Press).

Paulson’s field guide has a distribution map for each species with the species descriptions and pictures – so likely from unlikely species are easily separated. As well as color pictures of mature males and females, plates with line drawings showing male genitalia (claspers) and critical female characters are presented for easy of comparison. Each species has paragraphs with a description and a review of key characters in comparison to similar species. Also, the natural history, habitat, flight season, and a comment on distribution are given. The only complaint I have is that he relies too much on the common, rather than the scientific names – but this complaint may be restricted to entomologists.

Odonate Family Genus species   Moose Pasture  Home Bug Garden

Aeschnidae Aeschna interrupta                +                +

Aeschnidae Aeschna eremita                      +                 -
Corduliidae Epitheca spinigera                   +                -
Libellulidae Leucorrhinia cf hudsonica        +                 -
Libellulidae Leuchorrhinia intactor             +                -
Libellulidae Libellula quadrimaculata       +                +
Libellulidae Sympetrum internum             +                +
Libellulidae Sympetrum danae                  +                +
Coenagrionidae Coenagrion resolutum     +                 +
Coenagrionidae Enallagma cyathicerum      +                -
Coenagrionidae Enallagma ebrium              +                -
Coenagrionidae Nehallenia irene                  +                -
Lestidae Lestes congener                             +                -
Lestidae Lestes disjunctus                          +                 +

Lestidae Lestes dryas                                  -                 +

(excuse the drunken columns - Blogger seems to have trouble with tables. Bold = shared species. Red = HBG only)

As usual, you should take all my identifications with a grain of salt, but in this case if there are any errors, they are probably applicable to both sites. Also, we have many unidentifiable pictures of damselflies, so their actual diversity is probably higher. With damselflies, and I suppose this is ironic, dead males on a pin are the best route to a solid identification.

 So, of the 15 species identified to date, 6 occur both at the Moose Pasture and in our backyard, and only one, the Emerald Spreadwing (Lestes dryas) has yet to be identified at the Moose Pasture. A quick reading of Paulson suggests two reasons for this apparent difference. The Emerald Spreadwing favours shallow densely vegetated ponds (sounds like our backyard pond) and oviposits in live sedges, grasses, and horsetails (the pond is full of sedges). Permanent water bodies are not favourable breeding sites for this species.

Although our backyard pond has only about 2 m square of surface area, it does have lots of emergent vegetation and the bubbler to keep it aerated. At the Moose Pasture, Dancing Elephant Lake (DEL) and its attendant marsh and pond cover about 28 acres. The topography results from stagnant chunks of glacier that were left behind the main retreating mass and formed kettles surrounded by knobs (now covered with aspen) There is much emergent vegetation, and also lots of aquatic marcophytes and some deep areas without vegetation.

The difference between a lake and a pond isn’t well agreed, but usually lakes are expected to be larger and have some area too deep for rooted plants, and DEL seems to just qualify. One of the neighbours calls it a slough, but ‘slough’ is as loosely used as ‘lake’ for everything from an alkaline prairie pothole, to a treed swamp, to a marsh. The only trees in DEL are the skeletons of the willows drowned when the beaver flooded out the meadows that we now call marsh, which to us means it is weedy and shallow enough that getting the canoe through is difficult (The Trunk and Lower Legs). But whatever you want to call it, a host of odonates emerge every year.

The same is true for our backyard pond. Well, maybe ‘host’ is an exaggeration. However, we do have yearly emergences of many damselflies and some dragonflies. It is a rare summer day that one or more of these attractive and useful insects isn't around. They eat other insects, and so we can think of them as good ‘natural enemies” – and if they take any bees, it is only the tiny ones.

And what can we conclude, if anything, from this data? I’ll argue that even a small backyard pond can act as an urban refuge for a subset of the local odonates. This exaggerates the usefulness of the pond for dragonflies – the 4-spotted Skimmer was a one-off (possibly brought in with a plant) and the Variable Darner (Aeshna interrupta) may cruise through your yard even if you don’t have a pond.

 The Cherry-faced and Black (S. danae) Meadowhawks, however, breed in the pond as do several of the bluet damselflies. The Emerald Spreadwing finds a small pond a perfect habitat. In Edmonton, where synanthropic mosquitoes that breed in small accumulations of water are absent, there is no real downside to a backyard pond – the birds love it, the bubbler adds some relaxing white noise, water plants are interesting, and a host of aquatic insects, snails, and other even smaller invertebrates can make a living where dandelions and grass once dwelled.

Aculeata Agnoistes: The Prairie Yellowjacket Vespula atropilosa

In general, I try to adorn this blog with as many of my wife’s pictures as possible. After all, she is the photographer (and the one with the cumbersome and expensive camera gear). I’m strictly the put-a-name-on-the-bug person. And when it comes to cameras, I’m strictly a point-and-shoot person. As a result, I rarely come up with an insect picture that is of much use. This isn’t entirely the camera’s fault – people like Terry Thormin and an earlier Ted MacRae (who has now moved on to a real camera and even more spectacular photos) have produced numerous great insect photos with point-and-shoots (and Alex Wild can even produce good pictures with a cell phone) – but for anything that isn’t large and slow-moving, putting me and a point-and-shoot (originally a CoolPix 5700 and now a Lumix DMC-FZ28) after them is mostly a lesson in humility. To me the worst affliction of point-and-shoot insect photography is the interminable delay between pressing the button and the camera snapping the picture.

In this case, a colony of the Prairie Yellowjacket Vespula atropilosa under the steps in the garden in front of Government House, my wife was not around and I had to be the photographer. I won’t share the two dozen beautifully focused pictures of the wasp-less steps with you. Still, with enough persistence and cooperative bugs, even I can acquire images adequate to document the identity of an insect. Usually I would use the Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region to identify a yellowjacket. However, as is true of so much of Canadian life, the Atlas only works for species in the East. The Prairie Yellowjacket is a western species and reaches its northeastern distributional limit in Edmonton: it isn’t in the key.

If you used the Atlas more or less correctly, you should end up in the rufa species-group before your started to founder. The two yellow spots on top the first abdominal segment are helpful – if mostly fused to the posterior yellow band. If you made some wrong choices, you might end up in the vulgaris species-group and start to feel like I do when using my point-shoot to take a picture of an insect. When the characters on your insect and those in the key start to diverge widely, it is usually a sign that somewhere you have made a wrong choice.

Learning the true name of a yellowjacket may seem like a bit of an egghead thing, but if you were trying to decide if you needed to eliminate the nest, it could be quite useful. In general, rufa group yellowjackets mind their own business and spend their time hunting insects to feed their brood. That means you could consider them useful ‘natural enemies’. If you stir up the nest, yes they will attack and sting you (so will bumblebees), but otherwise you might hardly notice them and probably most of what they eat wouldn’t be missed.

Vulgaris group species, however, will both hunt and scavenge and are quite willing to share whatever you are trying to eat or drink – and if you object, they are happy to sting you. They also have larger colonies and tend to be more aggressive. Every spring I eliminate any vulgaris group species trying to take up residence in my yard. This usually means the Western Yellojacket Vespula pensylvanica (it gets just east enough to be in the Atlas). I also take out the Baldfaced Hornets Dolichovespula maculata. In contrast to species of Vespula that tend to nest underground, Dolichovespula tend to nest in trees and shrubs (or on fences) where you are more likely to bump into them. The Baldfaced Hornet is the largest and most aggressive member of its genus and it pays to go after the nests when they are small.

Like other members of its hunting group, the Prairie Yellowjacket tends to nest underground and to have smaller nests than vulgaris group species – a few hundred rather than a few thousand workers. Unfortunately, although “restricted to the Canadian and Transition Zones of the Boreal Region”*, the Prairie Yellowjacket is also happy with the open areas we create such as golf courses and parks, so even if you mind your own business you may encounter this wasp. You can learn a fair amount about it – and even have a good chance of keying it out correctly – if you consult Akre et al. (1981)*, one of those great monographs that the USDA used to produce. You can also find most of the information and illustrations from this book on line at Discover Life. I suppose I might regret it, but if a Prairie Yellowjacket decided to nest under my steps, I think I’d let it.

*Akre, R.D., A. Greene, J.F. MacDonald, P.J. Landholt, and H.G. Davis. (1981). Yellowjackets of North America, North of Mexico. U.S. Department of Agriculture, Washington, D.C. Handbook #552.

Aculeata Agonistes: Ants, Aphids & Aspen

The Home Bug Garden doesn’t look like the picture above, that is of our Moose Pasture about 55 km to the East as the raven flies, but it may once have. Both are located in the Aspen Parkland biome, named for its dominant tree, Quaking Aspen (aka White Poplar) Populus tremuloides, and its park-like mixture of open grasslands and patches of trees. In the Prairie Provinces of Canada, Aspen Parkland is rich in postglacial water bodies. And, as my late father-in-law pointed out repeatedly, he used to going boating in what is now our neighbourhood when he was a boy.

The prairie parklands occur across a broad stretch of central Canada, but aspen parkland also extends well to the south in the Rockies. South Park in Colorado, made famous by the potty-mouthed cartoon, is just one of many such mixtures of aspen and meadow. Interestingly, parkland is considered a transitional biome between prairie and boreal forest. It’s as if it isn’t really a natural system, but somehow aberrantly refuses to become its destiny: conifer forest if moisture remains high enough and fire frequency low enough or prairie if the opposites occur.

We love aspen, but whenever I find a seedling growing in the HBG, I grub it out. This is an entirely practical behaviour: aspen roots have a reputation for seeking out and clogging water and sewage pipes. Unfortunately, that means we miss out on a lovely tree and all but a passing acquaintance with many of the insects associated with aspen. Not all though, there appears to be at least one aspen-associated aculeate hymenopteron that finds both the Moose Pasture and our yard agreeable: the Black Mound Ant Formica podzolica Francoeur, 1973.

In zoological nomenclature, the year that comes after the author of a species name refers to when the diagnosis of a new species was first published. In this case, I haven’t inverted the 9 and 7 – this species name wasn’t properly sorted out until 1973. Before that it travelled under several names including the widely distributed Formica fusca. Insects tend to be interesting in direct proportion to how much one can learn about them and unless one can first learn their real name, such information as to make them interesting neighbours remains elusive. Ant species are particularly difficult to identify – species level keys are technical, and, well, many ant species tend to look alike. This seems to be especially true of Formica species. In this case, we are indebted to James Glasier for identifying the black ants that caught our attention with their herds of speckled aphids on young aspen as Formica podzolica (misattributions in any other images are mine).

Although the scientific name may be relatively new, people in my neighbourhood have been at war with black mound ants since soon after the first expanses of green lawns rose out of the former slough. Formica podzolica excavates and piles up largish mounds of black clay wherever it feels at home here and no one seems to find lumpy lawns attractive or interesting. In the bush, though, the mounds are an interesting feature and the black ants seem much less aggressive than their red and black neighbours Formica aserva.

I’m less than excited by ants, but no lover of lawns, so generally I leave my ants alone as long as they leave me alone. Unfortunately, ants are infamous for guarding patches of sap-sucking homopterons (aphids, hoppers, and the like). They protect these annoying insects from ‘natural enemies’ such as ladybird beetles, lacewings, and small parasitic wasps. ‘Natural enemy’ is another of those bizarre concepts that has somehow become commonplace. Are there unnatural enemies? Well, I suppose Count Dracula’s cockroach-munching Igor would do. In any case, usually ‘natural enemy’ refers to an arthropod that eats or parasitizes an arthropod that eats something we value. Ants can be natural enemies, but not when they are guarding aphids. By chasing off or killing things that want to eat aphids, ants allow plant lice (= aphids) numbers to rise, the amount of sap they drink to increase, more honeydew to spatter, and sooty molds to cover leaf surfaces. None of this would seem to be good for the plant, but the ants benefit by ‘milking’ the aphids for their honeydew and the aphids are assumed to do better with the guards.

Two things especially intrigued us about the black ants and their aphids on the young aspens, and the first was that the aspen leaves have a pair of nectaries (red spots where the petiole joins the leaf under the leg of the top ant). That plants can produce nectar in flowers to attract pollinators is well known, but nectar-producing glands are not limited to flowers. As a group (and giving an indication that scientists were once surprised to find this out themselves) nectaries not in flowers are called ‘extrafloral’. Ants are known to be attracted to extrafloral nectaries, and one can imagine that having aggressive black ants scuttling around one’s peony buds could be a good thing when some hungry caterpillar was on the prowl for a meal. But why would aspen want ants on their leaves if they end up tending aphids? This particular aphid is a well known pest of aspen – the Poplar Leaf Aphid (aka Speckled Poplar Aphid) Chaitophorus populicola (thanks to Bryan Brunet for the id).

Fossils in the Florissant beds in Colorado demonstrate that members of the genus Populus have had nectaries and been associated with ants and other predatory insects for at least 35 million years (Pemberton 1992. American Journal of Botany 79:1242-1246). Just why aspen have extrafloral nectaries, however, isn’t very clear since they do not seem to influence natural enemy abundance (see Wooly et al. 2007. Annals of Botany 100: 1337–1346). Of course, just calling an insect a natural enemy doesn’t make it useful to a plant (or a gardener). Ambush bugs and crab spiders, for example, make their livings hiding in flowers and eating pollinators.

So perhaps we have good natural enemies that help the plant and get their reward at extrafloral nectaries and other bludgers that just take a sip and go about their not very helpful lives. Life, however, is usually not that simple. For example, the usefulness of extrafloral nectaries may vary with age (younger aspen have proportionately more nectaries than older aspen) and time of year (many nectaries are known to dry up after young leaves have hardened off in early summer). So, ants may be useful for keeping caterpillars away in the spring or on young trees (which have fewer leaves they can afford to lose). Perhaps the ants don’t start farming aphids until after the trees cut off their supply of nectar. Perhaps later in the summer, when leaves will soon be dropping anyway, aspen find it less expensive to let the ants get their sugary rewards second hand from the plant lice than to feed them directly from extrafloral nectaries. There are enough ‘perhapses’ in this simple system to keep a host of scientists busy for years.

Speaking of which, Kailen Mooney & coworkers have found out something interesting about our black ant on pine trees in Colorado. There Formica podzolica herds large aphids in the genus Cinara. I once had a job dissecting Cinara aphids and looking for parasites – 10,000 aphids yielded only 3 parasites, so perhaps our black ant is a good Cinara shepherd (or I was a really bad aphid vivisectionist). However, Mooney found that birds were able to eat both ants and aphids, reducing the latter by 91% (those not eaten dropped to the ground) and causing the ant to look for less dangerous meals. That was good for the pine trees, so birds can be elevated to ‘natural enemies’ here. Black Mound Ants were good for the aphids only when birds weren’t around. But as usual, the story is even more complicated. As well as Black Mound Ants, another species in the same genus, Formica planipilis, also guarded pine aphids. This ant was a better aphid husbander even when birds were around (see Mooney & Mandel 2010. Oikos 119: 874–882 and references therein). I’m starting to feel a little bit sorry for the aphids that Black Mound Ants decide to protect.

This feeling is reinforced by a closer look at our erstwhile aphid farmer: several predatory hoverfly larvae are eating aphids right under the noses of the ants! Apparently the ants are oblivious to the foxes in the hen coop, or perhaps too nervous that a Yellow Warbler may swoop down and eat them to notice. Also, they may be being fooled by the hoverfly larva into thinking the maggots are aphids.  Syrphus ribesii uses its cuticular hydrocarbons to smell/taste like the wooly alder aphid and protect themselves from guarding ants (Lohman et al. 2006. Ecological Entomology 31: 41–51) and this may very well be happening here.

If you can think of being tended by ants as a characteristic of an aphid species, then you could ask the question, we’ll I wonder how many times it evolved in Chaitophorus aphids feeding on poplars and willows? Shingleton & Stern (2003. Molecular Molecular phylogenetic evidence for multiple gains or losses of ant mutualism within the aphid genus Chaitophorus. Molecular Phylogenetics and Evolution 26: 26–35) asked this very question and found that it appears to either have been acquired by several aphids independently or to be a fairly unstable character that has been lost multiple times. Considering this particular association and the results of Mooney and her coworkers, one wonders just how beneficial it is for an aphid to be associated with the Black Mound Ant?