Biodiversity Gone Bad: Hornets in the Home Bug Garden (updated 19 Sept 09)

Home bug gardening isn’t the most easily understood avocation. At work my colleagues make fun of me not wanting to kill the insects in my yard. My revolving neighbours on one side, a rental, persistently think that I am a botanist. No many how many times I tell them I’m a bug gardener, it just doesn’t compute. The neighbour on the other side has known me 7 years now and I thought she understood. But, when I proudly proclaimed to her last week that I had identified 9 species of hornets and yellowjackets from my backyard, she seemed nonplussed, or perhaps creeped-out.

Before someone goes running for the bylaws or the bug spray, let me make one thing perfectly clear: as far as I know, I don’t have any hornets or yellowjackets nesting in my yard. In fact, on the first cold night after finding a bald-faced hornet nest on the fence this Spring, I nuked it. The yellowjacket queen that tried to nest under the garage was first flooded, then buried and, those efforts proving entirely ineffectual, finally netted and smashed. There may be a nest hidden somewhere on my lot, but based on the trajectories of the visiting hornet workers, I’d say I have my neighbours to thank for my astonishing vespine diversity.

And an astonishing diversity it is – it looks like most of the hornet species likely to be found in this part of Alberta are lurking within flying distance of my backyard. Not only that, but they find the Home Bug Garden entirely worth a regular visit. This conviviality is no doubt due to two aspects of the garden: ready access to water and lots of umbels. Actually, there may be a corymb or a cyme or two, and there are certainly some corymb-like (yarrow) and otherwise racemose (goldenrod) clusters of composites that attract wasps, but as I repeatedly tell my neighbours in the rental, I’m really not a botanist. In any case, the umbels clearly get the most attention from simple umbels (milkweed) to compound umbels (dill, lovage, caraway, chervil). The good news is that most of the wasps fooling around on flowers are males – and these can not sting - and most of the ones that can are really more interested in bugs than in people.



Wasp is a general term, but for most people it refers to the social members of the family Vespidae that have the ability, and the willingness, to sting repeatedly when disturbed. This is mostly a behaviour of the workers – the reproductively suppressed females – who have no problem jabbing their modified egg-laying organ (ovipositor) into your skin and injecting lots of toxic and allergenic chemicals. Although it is possible to die of envenomization from wasp stings, almost every one who dies after being stung is a victim of anaphylactic shock and a single sting can kill a susceptible individual. Queens are much bigger than workers, and so more intimidating, but are usually only seen in early Spring and briefly in the Fall. Male wasps are harmless flower philanderers, but look pretty much the same as the workers (actually, they have longer antennae and one extra abdominal segment, but when you have a yellowjacket wanting to share your pop, these aren’t the easiest characters to see). So generally, keeping safe means keeping away from nests and from foraging workers.



The family name Vespidae comes from Vespa, the Latin for wasp, and also the genus name for the Giant European Hornet – a truly large wasp, large enough to feed on honeybees and yellowjackets when it feels like it, pretty intimidating in person, and also having the garden-unfriendly habit of girdling twigs so that it can feed on sap. Unfortunately, the European Hornet, Vespa crabro, was introduced to North America and is well established – but fortunately for Edmontonians, only in the East. Easterners also are well familiar with the paper wasps in the genus Polistes, but the only Albertan species, Polistes aurifer, appears to be limited to the south. That’s good, because Polistes nests are often placed on shrubs, fences, window wells, and other places you are likely to stick your hands without looking, and if you blunder into one, you will get covered by stinging wasps. What we Edmontonians get are Vespula (‘little wasp’) and Dolichovespula (long little wasp – they have a rather long face). Species of Dolichovespula tend to nest above ground in those grey football-like paper nests and species of Vespula tend to nest below ground in old rodent burrows or the like, but there lots of exceptions, especially when it comes to taking advantage of hollow spaces in human habitations.

Before I get into the specifics of my HBG wasps, let me highly recommend these two publications (from which I will borrow information freely):
Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region by Matthias Buck, Steve Marshall, and David Cheung in the Canadian Journal for Arthropod Identification
The Yellowjackets of America North of Mexico. by RD Akre, A Greene, JF MacDonald, PJ Landolt, and HG Davis. 1981. Agriculture Handbook, 552. United States Department of Agriculture, Science and Education Administration, Washington D.C. 102 pp.

UPDATED 19 September 2009: Large V's of gruking sandhill cranes have been flying south over the Home Bug Garden; orange-crowned and yellow-rumped warblers and white-throated sparrows have been splashing around the bird bath; and the leaves are yellowing fast. Yellowjacket season will soon be over, perhaps next week, as frost is threatening. Time to polish up this post and bid adieu to some of our least loved bugs.

No new species to add to the HBG, but Insects of Alberta has records for the Arctic Yellowjacket (Dolichovespula norwegica (Fab., 1781) ) from Calgary, so I'm a bit envious. From the picture, I'd say that 'yellowjacket' is a bit of a misnomer - looks like a blackjacket to me - but nothern populations of vespids (including the solitary species) can tend towards 'ivory' markings.

To continue with the lack of good news, I have been able to confirm that the Evil European Wasp, Vespula germanica, is a member of the HBG vespifauna. The confirmation comes via the male genitalia (no pun intended, or at least not initially), so breeding populations are here in Edmonton. Excess confirmation for this colonization event came the very same day as the HBG event, when a nest was nuked at work and turned out to be V. germanica.

On the good, or at least interesting, news side, I have discovered (more likely rediscovered) a behavioural difference between the males of Dolichovespula and vulgaris-group Vespula. The former are the flower philaderers: greedy, flower frolicking, poseurs in aposematic bands.   The latter, at least for V. pensylvanica and germanica, are very mysterious delvers into the foliage of forget-me-nots - and seem not at all interested in flowers. Details are added below by species.



The Bald-faced Hornet - Dolichovespula maculata (Linnaeus)

These are our largest hornets, the only common black and white ones, and have a definite sense of entitlement. If you try to swat one away, it is more likely to buzz you, than to acknowledge your superiority and move on. They have attitude, but after a few minutes of in-your-face fancy flying, usually find better things to do. The workers take honeydew and other sugary things like pop, but mostly prey on live arthropods (especially flies visiting flowers in my garden) and sometimes preferentially on other hornet species. I watched one bald-faced wrestle another to the ground. I suppose I should have waited to see who won and what happened to the loser, but I was so shocked by the lack of sisterly solicitude that I stepped on both on them. Why can’t wasps just learn to get along? Anyway, the big, grey nests can be found up to 20m above ground in trees but also in or on human structures and in hollow trees. If you come across a nest, I advise you to leave it alone. Let someone else win the Darwin Award.

The Aerial Yellowjacket - Dolichovespula arenaria (Fabricius)

These are about half the size of the bald-faced hornets, and the more typical yellow and black in colour (see plate a few paragraphs above), but otherwise have similar behaviours. Nests are usually in shrubs or trees from near the ground to high in the canopy or in or around our homes. Workers are mostly interested in catching other insects for dinner, so they aren’t the worst guests at a picnic, but like any social wasp, if you disturb their nest, you are in for a bad time. The males are a constant presence on goldenrod and swamp milkweed throughout the late summer.

Northern Aerial Yellowjacket - Dolichovespula norvegicoides (Sladen)

This is my second favourite backyard wasp, mostly because workers are rare and inoffensive and the rest are harmless males feeding at flowers. Also, little is known about their biology except they tend to have aerial nests in trees and shrubs. Rare and mysterious is always more interesting than common and nasty. Males are common on swamp milkweed and early goldenrod in mid-August, but seem to disappear in September.




The Parasitic Blackjacket - Dolichovespula adulterina (du Buysson)

This is by far my favourite backyard hornet because it is the only obligate social parasite in its genus in North America (adulterina is now considered the proper name for the arctica in the USDA book). ‘Obligate social parasite’ means a queen D. adulterina infiltrates a nest of the Aerial Yellowjacket early in the season before the workers emerge, sneaks in its own eggs, and eventually kills off the yellowjacket queen. Now what more could you ask for in a hornet? Additionally, the males are an attractive ivory and black colour and pretty much mind their own business as they pollinate my plants.




The Blackjacket - Vespula consobrina (de Saussure)

Species of Vespula in our region fall into two species groups: the annoying vulgaris group and the laid-back and innocuous rufa-group. The Blackjacket and the next species, the Prairie Yellowjacket, are the only members of the rufa-group I’ve found in my yard to date. The Blackjacket looks a bit like a half-pint Bald-faced Hornet or a Parasitic Blackjacket but has a short face and slight differences in patterning. Like the rest of the rufa-group, these hornets are primarily interested in eating insects and aren’t likely to bother you. Actually, they have never bothered me, but I did kill a worker to confirm the species identification (and alleviate the snickering at work).

The Prairie Yellowjacket - Vespula atropilosa (Sladen)

This is the rarest of my backyard hornets and I don’t have any pictures. Edmonton is near the NE limit of its range. They nest mostly in rodent burrows or in rotting stumps and logs and have an interesting ichneumonid parasitoid, Sphecophaga vesparum burra (Cresson), that lives in its nests and parasitizes its pupae. In Washington State, 80% of Prairie Yellowjacket nests may be infested with the ichneumonid (which also goes after vulgaris-group wasps). Males wander into the HBG on a regular basis, but are difficult to document because they don't seem to have either the flower philandering or forget-me-not delving behaviours of the others. The few I have captured have been on-the-wing or resting on foliage.



The Western Yellowjacket - Vespula pensylvanica (de Saussure)

This is the main pest yellowjacket in my yard and probably in most of Edmonton, although we are near the northern limit of its range (apparently de Saussure had problems with his spelling as well as his distributional information since this wasp does not occur in Pennsylvania). The workers are aggressive, and although they do forage for insects, they also are attracted to dead animals including that burger, hotdog, or roast pig you are trying to eat at a barbie. They like soft drinks too (but seem to give wine a pass) and when you swat them away, they give you the buzz treatment. Nests are built in hollow walls and attics, as well as underground (probably what was trying to nest under my garage this Spring). They have a truly incredible parasitoid – the trigonalid wasp Bareogonalos canadensis (Harrington) – but that is a story for another post. The primary source of Western Yellowjacket mortality in my yard appears to be me, so there are lots of them buzzing my flowers for prey and my barbecue for meat.

Male Western Yellowjackets show an interesting behaviour in the HBG: they seem to like the foliage of forget-me-nots (Myosotis sylvatica). Actually, the foliage is a low and dense garden bed composed of forget-me-not, coltsfoot (Petasites palmatus), and bunchberry (Cornus canadensis), but the males are mostly landing on the forget-me-not (but that is most of the cover).

Once they land, the males crawl into the foliage and disappear. I've put my nose to the ground and watched a couple and they don't seem to do anything other than walk on the plants and perhaps apply their mouthparts to the leaf surface now and then. What is going on? I haven't a clue, but there is no sign of honeydew, queen yellowjackets, or any other obvious attractant, including prey (which presumably they aren't interested in anyway).

I missed these males for a long time, because I assumed they were workers, but nope, they are all males - and none are showing up on flowers. Very interesting - and this is also were I picked up a male V. germanica, so it may be a vulgaris-group behaviour. My current favourite hypothesis is that the males are collecting a plant compound that makes them attractive to females, but it took two glasses of wine for that idea to pop up, so in my current sober state I find it dubious.

The Vulgar Yellowjacket - Vespula vulgaris (Linnaeus)

In its European incarnation, this is the species that gives its name to the nasty vulgaris-group. Ours may actually be a different species, but it has all of the unfortunate behaviours that result in yellowjackets being unwanted guests. Workers go after a wide variety of human foods and kill the occasional bug when they are bored. Nests are usually subterranean but are sometimes also built in rotten logs or stumps, forest duff, hollow walls or even in trees. This is one of the two species of yellowjackets that have been introduced to Australia and New Zealand where they have become an ecological disaster and very annoying pests. In my yard Vulgar Yellowjackets were common earlier in the year, but have now been almost entirely replaced by Western YellowJackets and the next species.

The Evil European Wasp - Vespula germanica (Fabricius)

This species is the horror introduced into New Zealand early on; Hobart, Tasmania in 1958; Maryland, USA in 1968; around Melbourne, Victoria in 1977; and elsewhere around the World on various dates in its unending drive to conquer all. It does well it urban areas, seems to like to eat all the things we like to take on picnic, scarfs up all the sweets it can, and is very aggressive in taking its share of the meal. Nest are usually subterranean but are also built in hollow walls, in roofs, attics, and any other place where it can find an acceptable cavity. The species looks similar to the Western Yellowjacket and especially so here where the Western colour pattern can overlap that of the European Wasp. So far, I’ve collect three probable germanica workers in my yard, but it would be nice to catch a male and confirm that this wasp has indeed reached Edmonton and that we aren’t just seeing a melanistic form of the Western Yellowjacket. Or would it? Well, whatever would be nice, unfortunately I have collected a male, and the genitalia never lie. Males, or make that the one male I have collected, have a similar forget-me-not behaviour to the Western Yellowjacket (see above).

Deleo delirium: Maleficia delenda sunt!

There comes a time in the course of a home bug gardener’s life when events call upon him to take up politically incorrect tools and use them to defend and preserve all he holds dear. Or to paraphrase Cato the Elder: Passer domesticus delendus est! I guess the exclamation point is un-Latin, but then so are periods, and my Latin muse assures me that the passive periphrastic agrees in gender and number with the object that ought to be destroyed. So, no matter what you think Cato said, don’t think delenda or delendum here, but 3rd declension masculine Passer, and IMHO, they all have to go.

Why, you might ask, would someone who claims to be gardening for biodiversity urge that a bird, the alpha and omega of biodiversity, ought to be destroyed? If you are a blue-birder or have a purple martin house, then I guess you already know the bloody murder that house sparrows (HOSP) wreak. If blood and bird bodies don’t bother you, examples of HOSP attacks can be found here. Remember - don't look if you can't stand the sight of bloody birds.

This morning we pulled a dead red-breasted nuthatch from the nest box where they have been relentlessly worried by the larger, alien, invasive, and thuggish HOSP. (I’m making no pretense at being a scientist this morning.) The opening to the box is (deliberately) too small for a house sparrow and all they can do is get their head in far enough to peck. They can’t possibly use the nest box, but being bird-brained, I don’t expect they care. And that’s not all! The bloody HOSPs ate my peas! AHHH! What is a bird introduced to eat insect pests doing eating my garden plants? Bloody bad biology is what. Shades of the cane toad, the HOSP eats few insects and feeds mostly on seeds and plants!

What to do? You probably need a permit to even look at a bird with murderous intent, let alone wring its neck. Ha! Unfortunately for the HOSP, in Alberta they are considered invasive pests, and the Province offers lots of permit-free advice on how to reduce their populations. Firing off shotguns within city limits and spreading poisons aren’t among the things one can do, but trapping is encouraged. Well, more or less. According to Chris Fisher & John Acorn’s “Birds of Alberta”, HOSPs arrived here in 1898 and “People with a dislike for this introduced ‘avian mouse’ go to amazing lengths to combat the species, but House Sparrows are here to stay.” And that certainly seems to be true – it’s hard to find a block in the City where you can’t hear their constant cheaping. It's enough to make you want to squeeze them until their eyes pop out.

And then there are all the other maleficent pests scourging the garden. Formica fusca delenda est! Based on the number of people in Edmonton who whiten the ant mounds in their lawns with boric acid, I suspect the opinion that the black ant must be destroyed is widely held. Since I have no truck with lawns, though, I’ve held them no animosity. After all, ants really are extraordinary superorganisms, industrious, and often fun to watch. These particular ants appear to belong to the Formica fusca group and they can mess up my tiny patches of lawn all they want – but if they want to hang out in my garden, then they’d better be polite. This year they have been extraordinarily rude and their tunneling has already killed a purple sage and a hens-and-chicks and severely damaged a shrub cinquefoil. I tried soaking them with the hose to encourage them to move to a drier site. That does work sometimes, but not this year – a shovel and Dr Doom were required. That made me feel bad, but not so bad when I started looking around at all the collusion between aphids and ants.

Leaf miners, caterpillars, sawflies, spittlebugs, they are all bad, but there are aphids on everything! Aphididae delendae sunt!

A Gallery of Aphid Destruction

I agree with Gardening Zone 3b – where are the ladybugs and lacewings when you need them?

The natural enemies are out there, but I guess they don't like the cold wet weather any more than we do. Slowly they are coming on.


To paraphrase Betty Davis, there comes a time in every gardener's life when the only thing that helps is a glass of champagne. A couple hours with the squirt bottle of soapy water will have to come first though.

Beware the Lord of Flies: Behold the Antipollinator!

Although bees and wasps (excluding hornets) are all that is industrious and good in a Home Bug Garden, not every insect is as honest about its identity or intentions. This very waspy looking fly is a bad example.

Far from being a friendly wasp, this demon from the fires below is a killer of pollinators: a Thick-headed Fly (Diptera: Conopidae: Physocephala sp.). In his book Insects, their natural history and diversity, Steve Marshall refers to conopids and their relatives as ‘Killer acalyptrates’ and with unholy delight describes how “bumblebees visiting flowers on a sunny day” are attacked by these “dipterous divebombers”. These depraved dipterons attack bees and wasps in flight, not to feed on them directly, but to leave behind an egg that will hatch into a parasitic maggot that will eat them alive from the inside out. No wonder Beelzebub is called the Lord of the Flies!

Take the time to look at this imposter closely and its infernal flyness will jump out at you. Bees and wasps have two pairs of wings, but Di-ptera have only two functional wings. The rear wings are modified into organs called halteres that help them maintain their balance when executing the sharp turns that allow them to make food of bees in flight (or feed on our blood or deposit eggs where we don’t want to know). Then there is the fixed proboscis that looks rather like the stabbing mouth of a tsetse fly, rather than the flexible tongue of bees. Finally, there are the devil-like horns instead of the graceful multi-segmented antennae of bees and wasps.

If these flies were attacking the queens of the yellow jackets and bald-faced hornets that were so common this Spring, then I would cheer them on. Every dead queen hornet is one less hive and many dozens fewer hornets at the barbie. Alas, according to Marshall, species of Physocephala are known to be parasitoids (the technical term for an insect parasite that kills its host) of honeybees and bumblebees. Let’s be bunt – they hate your flowers, fruit, and vegetables. Isn’t that always the way? All the really interesting bugs that show up are doing things you’d really rather they didn’t and not doing the things that you’d like done.

Here’s another other example of a killer fly – one that looks much more like a fly. Well, let’s be fair – it’s a bloody good-looking bug. Steve Marshall refers to these sciomyzid flies as “Snail killers”. Rather than tormenting useful pollinators, their maggots devote their deplorable de gustibus to mollusks. Well and good if only they were attacking the introduced, alien, destructors in the genus Deroceras – the totally without merit and abominable European Garden Slug. Given the current (and much appreciated) relatively wet June, these buggers will be on the slime march.

Alas, this sciomyzid is most likely interested in the harmless, even useful, aquatic lymaeid snails (see Marshall p. 417) that help keep the algae in our pond more or less in control. Does Nature really care anything at all about its balance in my garden? Of course not! What a bloody stupid question to ask. Am I the only too credulous gardener? I wonder how the Obama vegetable garden is going – forget the lead, what about the bugs? If it turns out the Secret Service is doing some late night pesticide appilcations, I may have to have a rant. Oh, who am I kidding? My first true rant is almost written.

A Short Ode to Pollinators, mostly Bees

I’d like to second Gardening in Zone 3b’s salute to Bug Girl’s Blog for her excellent coverage of National Pollinator’s Week in that large country to our south and especially for her post on ‘Homes for Pollinators’. Devoted readers (reader?, late night insomniac?) may remember that I was lamenting my dearth of information on just that topic a few posts ago. Now I have a wealth of information to digest on how best to make the Home Bug Garden a better place for bees to nest.

Goodbye to old favourites, native and alien: Winter Kill 2008-9

Rain, glorious rain! Last night, unexpectedly, we got 11.28 mm (yes we have a digital rain gauge, so take the last digit on faith). That’s not even half an inch, but brings our HBG total to 26 mm (just over an inch) since Mayday. Looks like more is on the way too, so although that means our planned Sunday Moose Pasture hiking/canoeing is cancelled, I can plant out the last of the seedlings and catch up on blogging.

Last Fall was very dry, the Winter harsh, and the Spring non-existent. Although the snow cover this Spring was good, it came on late (no snow cover until mid- December) and from 13 December through 9 January every night-time temperature was between -10 and -35 C. The rest of the Winter and Spring experienced repeated bouts of extreme cold with -30 as late as 10 March, the last killing frost (-4) on 22 May (three weeks after the usual last frost date), and the last light frost on 9 June.

The harsh weather is no doubt responsible for the devastation of last Fall’s bulb blow-out (~380 new bulbs went in). Although the established and new crocus, squills, chionodoxa, muscari, and species tulips did well, and quite a few of the new hybrid tulips and daffodils survived and put on quite a display, many were frost blasted and there’s been no sign of others. No sign either of the new Snowdrops (Galanthus nivalis), Checkered Fritillary (Fritillaria meleagris), spendy Lilac Wonder Dog’s Tooth Violet (Erythronium denscanis 'Lilac Wonder') , Spanish Bluebells (Hyacinthoides hispanica), or Grecian Windflowers (Anemone blanda). Not much surprise with the last two – Zone 4-5 plants that have failed before - but the others were all Zone 3, well mulched, watered in, and should have survived (well, maybe not the Lilac Wonder – a bit floppy when they arrived and that is not a good sign with lily bulbs).

The few Alberta native bulbs that I have (Western Wood Lily Lilium philadelphicum, Nodding Onion Allium cernuum) don’t show themselves until late spring. They are just now in bud. None of the bulbous MIAs are ‘native’, so perhaps they just aren’t well adapted to this life. But the established ‘alien’ bulbs seemed to come through pretty well and without them, the HBG would have been pretty bleak this April and May.

The perennials were pretty badly winter whacked too, with 18 no-shows and 3 more that put up a leaf or two, but are on their last roots. Below I’ve divided them into North American Native or ‘Alien’ listed them with the year they went in and their putative USDA Zone rating. There is no obvious pattern by origin: mortality is about equally divided between exotic and North American natives, including 3 plants native to Alberta (a wild bergamot and two sunflowers).

R.I.P. North American Natives Winter 2008-9:
Doppleganger Coneflower, Echinacea purpurea ‘Doppleganger’ 2005 Zone 3
Purple Joe-Pye Weed, Eupatorium purpureum 2008 Zone 3
Wild Bergamot Monarda fistulosa 2003 Zone 3 (AB native)
Garden View Scarlet Bergamot, Monarda didyma ‘Garden View Scarlet’ 2005 Zone 3
Maxmillian Sunflower Helianthus maxmillianii x 2 2004 Zone 3 (AB native)
Sunset Strain' Bitteroot, Lewisia cotyledon 'Sunset Strain' 2008 Zone 4
Purple Leaf Coral Bell, Heuchera americana 'Purple Palace Select' 2005 Zone 4

On the ropes (a couple of leaves left):
Chocolate Mint Foamflower, Tiarella 'Mint Chocolate' 2006 Zone 3
Iron Butterfly Foamflower, Tiarella 'Iron Butterfly' 2007 Zone 3
Ruby Spice Summersweet, Clethra alnifolia 'Ruby Spice' 2007 Zone 4

‘Aliens’ lost this winter:
Fernleaf Yarrow, Achillea filipendulina ‘Cloth of Gold’ 2005 Zone 2
Giant Yarrow, Achillea grandiflora (or maybe Tanacetum macrophyllum) 2005 Zone ?
Monkshood, Aconitum napellus clump 2004 Zone 2
Yellow Loosestrife, Lysimachia punctata ‘Alexander’ x 2 2004 Zone 2
Bronze Garden Mum, Chrysanthemum x morifolium 'Morden Delight' x 2 2006 Zone 3
Siberian Bugloss 'Jack Frost', Brunnera macrophylla 'Jack Frost' 2008 Zone 3
Siberian Bugloss 'Spring Yellow', Brunnera macrophylla 'Spring Yellow' 2008 Zone 3
Chinese Lanterns, Physalis alkekengi franchetii 2008 Zone 2b

March 1, 2159 or Pollinators Not

This morning the clock in the train station claimed it was March 1, 2159. Well maybe it meant that is the earliest we can expect warm weather. In any case, it gives me an excuse to follow up the post on pollinators with one on pollinators not, and display a few more Bug Garden visitors.

Not every arthropod ones finds in a flower is searching for nectar or pollen. Lots of them are there for another kind of feed. That can be interesting, especially if you like predatory insects like the Damsel Bug above, or spiders:





Or it can be disconcerting if you are hoping for fruit or seeds. But the toll that predators take on pollinators is unlikely to be of much importance in yield. Much more insidious are those that have nothing but bad intentions.



I remember how pleasantly surprised I was, that first Bug Garden Spring, at the extraordinary diversity of of sawflies that were visiting flowers. Except for diprionids long ago when I was a forest entomologist, I can't say that I ever had much experience with that branch of the Hymenoptera and I was entranced. Well, now I know better and I've come to an accommodation with most. A few leaves here and there are a small price to pay. The ones that defoliate the currant, columbine, and creeping jenny, though, get a population reduction treatment. They are messy buggers to squish between the fingers, but that's life.






And there are a few of these non-pollinating flower-visitors that are just too attractive not to like, like the tephritid fly below. We have planted lots of goldenrod for the late-summer colour and pollinators, but we don't mind hosting a few gall flies too.

Gardening for Pollinators meets Lord of the Flies

Another week, another threatened frost: such is Spring in a Zone 3 Bug Garden. Oh well, I should stop whinging and just get on with it. The HBG was first envisioned as a home for pollinators, which I suppose we thought of as mainly bees and butterflies. Well, not really, since at one time or another we have both taught pollination ecology, but embryonic bug garden thoughts aren’t necessarily very deep and butterflies, bees, and flowers was the general idea.

Not that we wanted to see lots of honeybees (another Australian anti-alien bias), but with the spread of the varroa bee mite and the emergence of the mysterious Colony Collapse Disorder, our primary pollinator has been on the ropes for some time now. In Alberta, a harsh climate and marauding bears mean that the only honeybees you are likely to see come from well defended bee keeps. Apparently no one near us has a backyard hive, because Apis mellifera is a rare visitor. That is too bad if you like cherries, saskatoons, apples or other home-grown fruit and vegetables, but there are alternative pollinators that have been attracting attention now that the tried and true honeybee is on the wane. There’s even a web resource page devoted to ‘Alternative Pollinators’ and, although a very high proportion of its links are broken and the functioning links often lead to questionable sources of information, the list supports the assumption that bees + butterflies = alternate pollinators.

Alberta has ‘native’ bees that can hold their own against the climate. Bumblebees (Bombus), leafcutter bees (Megachile), sweat bees (Halictidae), and digger bees (Andrena) are all reasonably diverse here. Our goal was to make the HBG their home by providing a more or less continuous bloom, and to reap our payback in produce. In that, I think we can claim some success, but it is small. Bees need more than flowers, and in particular, they need nesting sites. We did think of this a bit, e.g. planting shrubs with hollow twigs, but the most important of the alternative bee pollinators here are ground nesters and rodent burrows and bare patches of untilled soil aren’t exactly extensive in the HBG. Most of these bees are solitary and having a few dozen nesting in your yard isn’t going to do much for spring flowering fruit, especially since the most efficient of these, the leafcutter and bumblebees, are mostly summer visitors.

Leafcutter bees are a bit of a mixed blessing, since they certainly live up to their name, but they more than pay back the linings of their nests with efficient pollination of most of the veggies in the garden. Unlike most pollinating bees, megachilids collect pollen on their long body hairs and not on special pockets on their hind legs.

Bumblebee colonies take a while to grow and there is a distinct hiatus around now when the first brood must be pupating and the queens taking a well deserved rest. Add to that yet another late, cold spring and the result is cherry trees covered in silent blooms.

Of course bees are not the only pollinators. A variety of other Hymenoptera (ants, sawflies, wasps), beetles, butterflies, and flies come to flowers – or at least to certain kinds of flowers. Spreading, open inflorescences like those found in the carrot family or composites can accommodate a high diversity of insects out for a good feed. Surprisingly, two-winged flies (Diptera) are perhaps the most abundant and diverse of these alternative pollinators. The flower or hover flies (Syrphidae) are perhaps the best known of these floral frequenters. In his "Insects - Their Natural History and Diversity" Steve Marshall says we should treat syrphids as "honorary butterflies" for their bright colours, expert acrobatics, and abundance in familiar environments. Such honours do seem to have been bestowed in the UK, where pocket guides to hoverflies are available and such giants in the pantheon of bug gardeners as Jennifer Owen have done much to document syrphid diversity and abundance in urban gardens. Alas, no such guides or documentation seem to be available here (John, are you listening?).

Many syrphids mimic hymenopterans with a sting such as hornets and bees, which no doubt makes hanging around flowers a bit safer. Beeflies (Bombyliidae) could be said to do the same and often have their mouthparts drawnout into elongate straws for sipping nectar in the deeper flowers. No such advantages in camouflage are apparent in what seem to me to be the creepiest of the dipterons that frequent flowers - blowflies (Calliphoridae), especially species of Lucilia (bottom two pictures in fly plate) that would seem more at home on carrion. Astilbe seems to be especially attractive to these flesh flies.

So if you just want flowers and happy pollinators, and don’t mind a preponderance of flies, think large, open inflorescences like astilbe, goldenrod, butterfly weed, yarrow, daisies, caraway, lovage, and the like. If, however, you want apples, cherries, saskatoons, currants, beans, peas, tomatoes, peppers and anything else that requires some skilled pollination, then you need bees, and bees need a home as well as food. I suppose it is well past time that I started learning what bumble and digger bees need to make a home.