Tuesday, August 28, 2012

I just want to bee ... Mistaken for a wasp by wasps

Spilomyia sayi (Goot, 1964), not a wasp, just a good mimic
Every summer from late July through August an unusual flower fly (Syrphidae) shows up in the Home Bug Garden. Many, if not most, flower flies are brightly and contrastingly coloured more or less like wasps or clothed in furry hairs like bees. But some look more like the stingers than others. That is true of this fly, Spilomyia sayi (Goot, 1964) (known in earlier works by the preoccupied name Spilomyia or Paragus quadrifasciatus Say,1824). 
Two syrphids of varying waspishness - both in looks and behaviour
As well as being coloured like many a vespine wasp, its antennae are longer and more wasp-like than most syrphids, its wings waspishly dark, and its demeanour as it struts across the heads of yarrow and goldenrod as recklessly fearless as any hornet. Most flower flies dodge quickly away when approached, but not Spilomyia sayi. In fact, this fly is easy to catch by hand - in which case it emits a loud and very bee-like buzz.
Flies have died from time to time, and birds have eaten them, but how about wasps?
But who is Spilomyia trying to fool? Well, it is pretty good at fooling people, but the usual argument for this kind of Batesian Mimicry is bird brains. I suppose birds do eat flower flies, from time to time, but how often does a bird swoop down on a goldenrod or yarrow in a field? I can't say that I have ever seen this happen, but I have seen many a fly scarfed up from such flowers by patrolling hornets. Could it be that these flies just want to be left alone by their fellow insects as they gather some nourishment on flowers that are often covered in wasps (many of which are stingless males)? I suspect that predatory wasps and hornets have exerted more evolutionary pressure on these flies than any bird. Alas, behavioural ecologists seem obsessed with birds, so I am not sanguine about seeing any studies that test this idea.
Blackjacket (Vespula consobrina) - a likely model for and predator on our local Spilomyia

Saturday, August 25, 2012

Saturday Hopalong: Leaping from obscurity

In the beginning was soil - 1st stage nymph of grasshopper
Following fast on the first warblers, Autumn's first cold front has brought gloom, chilly winds, and showers to the Home Bug Garden. Bees are huddled on flowers and butterflies nowhere to be seen. Still, if the dimming sun manages to burn its way through the clouds this week, one of our largest insects may make an appearance, at least when startled into  a leap to safety. For the hopper has been around all summer, but rarely noticed.
Crypsis works best when insect and background share a long history
Western North America is famous for its plagues of migratory grasshoppers. Better known as locusts, grasshoppers in the genus Melanoplus ('black + add' or 'blackener', as when the skies are filled with locusts) may alternate between low-level populations of solitary individuals doing little harm and hordes of rampaging beasts. Although the most infamous of these, the Rocky Mountain Locust (Melanoplus spretus Walsh, 1866), is now extinct (as marvellously chronicled in Jeffrey Lockwood's Locust), we have others that breakout of their solitary mode from time to time. The Two-stripped Grasshopper Melanoplus bivittatus (Say, 1825) is one such and a large one at that.
Late stage nymph of Two-striped Grasshopper
Like other grasshoppers, the Two-striped starts its life as an egg in a pod in the soil. When they first hatch in May their colouration helps them to blend into the soil and snow-crushed detritus of last's years vegetation. But as they moult into later stages they green-up into the new foliage. As adults they change again to match the mostly vertical lines of their preferred grassy meadows and fields.
Large size + converging stripes are good field characters
Several dry, hot summers are thought to be needed to induce the migratory outbreak populations. When this grasshopper outbreaks it is a serious pest that will destroy field crops and gardens. But since the last two summers have been wet and often cool, it is reasonable to assume the hoppers natural enemies will hold them in check next year. So, this Fall we can just enjoy them as large, interesting grasshoppers, leaping up from garden and field and maybe munching on as many weeds as crops.
Two-striped embracing an evil weed - Canada Thistle

Thursday, August 23, 2012

Thursday Flutterby: Willows, dead leaves & hail

Migrating Yellow Warbler playing peekaboo in willow
The first sign of the coming Fall in the Home Bug Garden is usually some yellow in the trees. Around the middle of August, year after year, small yellow warblers start to flit around the willow, apple, and lilac growing around the pond and bird bath. Mostly these are Yellow Warblers (Setophaga petechia). At our place in the country, where water and willows abound, Yellow Warblers are present throughout the summer. At the city-mired Home Bug Garden, though, we only see them in transit, the first of the wave of southbound migrants and a reminder of yellow leaves to come.
Green Comma Polygonia faunus - a harbinger of dead leaves to come
Another willow aficionado also showed in mid-August this year: the Green Comma (aka Faun Anglewing) Polygonia faunus. The 'green' seems to refer to the narrow lichen-green marks near the margin of the underside of the hind wing (barely visible in the picture above). I think this is  male and perhaps hopeful that a agreeable female may also find the willow attractive. But if so, he will have a long wait - until next spring. In a month or so, he will have to find a place to hibernate amongst the fallen leaves. Meanwhile he enjoys the sun, when it shines, and whatever tasty bits of ooze he can find (these butterflies are not much interested in flowers).
The upper, much more lively side of the Green Comma
I'm pretty sure this butterfly is a Green Comma, that is I have talked myself into the identification and don't expect to be embarrassed by a real lepidopterist. But the Commas (from the silvery smile on the underside of the back wing) or Anglewings (from the jagged wing edges) are a difficult group with a number of very similar species in Alberta. For example, the Satyr Comma below.
Satyr Comma Polygonia satyrus near a nettle patch in the country.
The differences between the two species are subtle, but I have great confidence in this identification because specialists who actually work on the Satyr Comma agree with me. Its dead-leaf costume mixes into the gravel much better than on a green willow,  but shows its close relationship to the green Comma, as does its slurping up ooze
Satyr Comma with prominent comma and no green flecks
Although they may look alike, and act alike, these two butterflies function very differently as larvae. Caterpillars of the Green Comma feed on trees, especially birch, alder, and willow. The Home Bug Garden has birch and willow. The Satyr Comma's larvae, however, feed mostly on Stinging Nettle.  We tried nettle, but it is too painful for a home garden; however, they are supposed to also like hops, of which we have a bit. The hops is looking a little seedy after this afternoon's hailstorm, but perhaps next year a Satyr Comma will give it a go.
Hail storm - a spring, summer, fall aspect of the Home Bug Garden

Sunday, August 19, 2012

Adventures in Spider Misidentification: Six-spotted Fishing Spider

Six-spotted Fishing spider on Wild Rose
I'm pretty sure (that is I think) this is a juvenile Six-spotted Fishing Spider Dolomedes triton (Walckenaer, 1837). The white stripes along the carapace and abdomen and the striped femora are clues, and although it isn't fishing, it is perched near a lake and marsh. And then the abdomen does have a half-dozen pairs of white spots running down it. Unfortunately, the common name refers not to the easily seen abdominal spots, but to 6 large black spots on the sternum - something difficult to see unless the spider rolls over.
Six pairs of fuzzy spots yes, but not the definitive spots 
Charles Walckenaer was more whimsical, but no less obscure, when he named this species triton. The Greek god Triton is associated with the ocean, waves, and loud blasts of a conch shell as in "Or hear old Triton blow his wreathèd horn" (Wordsworth 1807). In the scientific realm, species of Charonia conch are called tritons, which does make sense since these snails do live in the oceans and their shells are used as trumpets. Also a moon of the planet Neptune (Latin for Poseidon, Triton's dad) is logically called Triton. But our spider inhabits the edges of marshes, lakes, and ponds. Perhaps, like Wordsworth, Walckenaer was yearning for simpler times, when naming our putative spider, or linking their hairy visage and aquatic lifestyle with the mermaid-like Tritons and ignoring the inconvenient seas. I think I like the last best and will absorb it into my "identification" of this week's lovely, hairy denizen of the water's edge.
Wild Rose with Tricoloured Bumble Bee
I'm pretty sure (that is I would stake a bottle of wine on it) that the fishing spider is sitting on a wild rose, but which wild rose I can't say. This is a bit embarrassing, since a wild rose is the Provincial Flower of Alberta, our licence plates proclaim Alberta 'Wild Rose Country', and even a political party has taken on its name. Although 'Wild Rose' is used loosely and rarely with specific identification, technically only one of the three species of wild rose in Alberta is THE Wild Rose: Rosa acicularis Lindley the Prickly Wild Rose. Since all three of these wild rose grow in the area and this isn't a post on 'Adventures in Plant Misidentification', I will remain mute on which species.

Sunday, August 12, 2012

Adventures in Spider Misidentification: Oviposition by spider

Mystery spider and desperate midge
Ted MacRae recently posted a picture of a tropical orb weaver that is enough to scare the bejesus out of any self-respecting arachnophobe. Did something similar happen here? I don't know. Other than knowing this is a male spider, by its palps, and a female midge, by her eggs, this interaction is a mystery to me. Did the spider squeeze its lunch too hard? Or is induced oviposition a viable strategy for saving a few offspring when captured by a predator? Who knows? Things are not always what they seem.
Pretty bee-friendly wildflower or noxious invasive weed?
For example this pretty 'wildflower' I discovered last weekend hosting a Tricoloured Bumble Bee turns out to be the insidious Common Tansy (Tanacetum vulgare) an introduced plant that is toxic to livestock that eat it. It's toxic to us too, but the chances of ingesting it aren't high unless you believe the Greek myth about it being an ingredient in the potion that turned Gandymede, a shepherd who had the misfortune to attract the attentions of Zeus, immortal. Still, some might be tempted, but you are more likely to go into spasms, foam at the mouth, and join the midge above in the hereafter, than achieve immortality. Tansy has had numerous external uses, for example as an insect-repellent, for embalming, to whiten the skin, and "to encourage the fertility of the sexual organs and to relieve sprains and headaches" (see previous link). However, for me it means spending Sunday afternoon coming into compliance with the weed act and removing it from my property.

Friday, August 10, 2012

Friday Phymatorama: Not as simple as it looks

Ambush Bug eating Cabbage White on Canada Thistle
This is the kind of picture any biological control entomologist or food-web modeller can instantly understand. The biocontrol person may see a natural enemy (the American Ambush Bug Phymata americana americana Melin, 1930) feeding on a pest (the Cabbage White Butterfly Pieris rapae (L., 1758)). If they are particularly perceptive, they also see that the pest is a potential pollinator of another pest, the misnamed Canada Thistle  Cirsium arvense (actually a native of Eurasia introduced here). So, the ambush bug is doing double duty. The food-web modeller might see it a little different: predator (bug), herbivore (butterfly), and primary producer (thistle), the typical three trophic-level food chain.
Ambush Bugs transformed into pests
Let's change the set-up slightly and look at another thistle. Here the female ambush bug (guarded by a smaller, darker male) is feeding on a Honey Bee (Apis mellifera L., 1758). The food web modeller doesn't see much different here, although they may wonder if the bugs would be better modelled as parasites of the plant (they are eating its pollinators). But, Hey! That's one of our bees! That bug is a pest, not a biocontrol agent/ natural enemy!
A slight change of focus turns good bugs bad
Let's change focus slightly again and look at another thistle plant. Here another pair of ghoulish bugs have a flower fly (Family Syrphidae: Helophilus sp.) by the tongue and the female bug is draining out its life's blood. Many flower flies are our friends, their maggots eat aphids, but this one's larvae feed on rotting vegetation. So, this is a more neutral interaction for our biocontrol person: the use of an alternative prey by a natural enemy/ pest of bees, depending on their perspective. This does complicate our food web model, though, the adult fly is an herbivore (feeding on pollen and nectar), but the larva is a detritivore (feeding on microbes and detritus), so a fourth trophic level needs to be added to the model as well as some omnivory (defined as feeding at more than one trophic level). The bugs are getting some of their energy directly from the detritivore level (as well as the herbivore level).
Flower fly that should've watched where it put its tongue
Let's shift focus slightly again, to another unfortunate fly. Here another pair of ambush bugs are feeding on a thick-headed fly (Family Conopidae), in this case Physocephala furcillata (Williston, 1882). Well, really the female bug is feeding and the male looking out for any other males that might be interested in his perch (but males aren't above sneaking a bite or two).
Ambush bugs feasting on a thick-headed fly
Our biocontrol specialist is likely to see this as more alternative prey behaviour. Good for keeping a predator around to feed on Cabbage Whites or bad if they are feeding on Honey Bees. But for the food-web modeller, this is just another complication.
Thick-headed flies mimic wasps, but are parasites of bumble bees
For our thick-headed fly is not a detritivore, but a fast-flying, wasp-mimcking parasite of bumble bees. They lay eggs on the bumble bees while they are in flight and the parasitic maggots eat out the bumble bees insides over a matter of a few weeks. This means we have to add another trophic "level" to our model - number 5 (detritivore, plant, herbivore, predator, parasite), at least as a concept, and because a predator feeding on a parasite is taking energy to one trophic level above the parasite (which in this case is functionally equivalent to our predator). 
Helophilus mimics a bee, but functions as both bee and detritivore (and dinner)
All of this is very destabilizing to our model food web: the more links (especially those between more than two levels), the more likely the model is to crash. And all of this comes from just looking at what one species of predator is doing on one afternoon in one field and on one plant. Imagine trying to model all of the interactions that must be going on in that one field with its dozens of plant and many hundreds of insect species. No wonder most modellers prefer to sit at their computers and play with their models and leave the real food webs to the bugs.
Not seeing eye-to-eye, but looking for the same thing: dinner

Thursday, August 9, 2012

Confessions of a moth addict: Underwings

Catocala briseis Edwards, 1864 Ribbed Underwing
I participated in International Moth Week mostly out of a sense of duty. Moths are grand, but they play second fiddle to butterflies for no good reason other than we are denizens of the day like the flutterbys and tend to be easily distracted by bright colours. And, as my friend Felix likes to say, phylogenetically butterflies are moths, so why not enjoy them all. So in the interests of justice to moths, I tried a few. Well, now I'm hooked and to celebrate my addiction here's a moth that looks a bit like a hybrid between drab mothdom and fluttery butterflydom: the Ribbed Underwing.
Monomaniacal eye-glow under the blacklight
Underwings used to be in the family Noctuidae, but now seem to reside in the Erebidae in the phylogenetically recalibrated Noctuoidea. More than a hundred species are known in North America and even the ones that aren't startlingly brilliant underwing are elegant and interesting. The caterpillars of this species feed on poplars and willows, and there is easily enough of them to go around at the moment. This was the largest moth that came to last weekend's blacklight, but nothing like a Polyphemus or a Luna Moth in size. Still, it was a bit of a thrill and now that I haven't seen one for a week, I'm starting to feel withdrawal symptoms.

Sunday, August 5, 2012

I just want ... a bee for dinner

Goldenrod Crab Spider curiously not yellow but hungry
Goldenrod (Solidago spp.), an unlikely looking relative of daisies, has been in bloom the last few weeks in central Alberta and hosting its usual surprising diversity of arthropods. The golden sprays are the perfect nectaring platform for wasps and bees and flies and butterflies and even the occasional moth. Yet danger lurks among even the most pastoral of golden fields.
Ménage à trois et d'une embuscade à trois
The bloom is off this goldenrod and our Goldenrod Crab Spider looks more than a bit out of place, but if she moves on to another in full bloom, then her colour will eventually catch-up with her and her hunting success increase. But other curiosities lurk among the golden sprays.
Male and female Phymata americana squared
In the case of the American Ambush Bug Phymata americana americana Melin, 1930 (Hemiptera: Reduviidae, Phymatinae), the females lurk much better than the males. Like the Goldenrod Crab Spider the ambush bugs can change colour from mostly white to mostly yellow. Additionally, the females have a light brown patterning that helps break-up their outline and blend them into the floral background so that they can carry out their nefarious designs with little chance of being noticed until they pounce.
Single-minded male spoiling a perfectly good camouflage
In contrast, male ambush bugs have much more extensive and darker coloration that rather ruins the illusion that they are not there. David Punzalan and his then colleagues Helen Rodd and Lock Rowe at the University of Toronto wondered why? Knowing that insects generally depend on the environment to regulate body temperature, that darker colours absorb more heat that lighter colours, and that males generally have one thing foremost on their minds, they devised and carried out a series of rather elegant experiments. They found that males with darker sides generally spent less time searching for females than males with lighter sides and that this difference was more pronounced during cool ambient temperatures. Similarly, when cooler temperatures prevailed, dark-sided males got the girls.
Darker sides = warmer males = more girl friends
 Interestingly, the variation in dorsal (top side) coloration had no detectable effect on male searching abilities or success rate. Perhaps the extra heat absorption isn't very important during the mid-day when the sun is more or less overhead or some other factor trumps dark dorsums.
Even ambush bugs sometimes get their colour-coordination wrong

Punzalan D, FH Rodd & L Rowe. 2008. Sexual selection mediated by the thermoregulatory effects of male colour pattern in the ambush bug Phymata Americana. Proc. R. Soc. B 275,:483–492 doi:10.1098/rspb.2007.1585
Punzalan D, M Cooray, FH Rodd & L Rowe. 2008. Condition dependence of sexually dimorphic colouration and longevity in the ambush bug Phymata americana. J. Evol. Biol. 21: 1297–1306 doi:10.1111/j.1420-9101.2008.01571.x

Saturday, August 4, 2012

I just want to bee ... a butterfly

Point-and-shoot dramatized Mourning Cloak chrysalis
This is just a quick post to point out the Update for the identifications for last weekend's backlight trapped moths and a chance to put another nail in the 'I just want to bee ...' series. Here's two examples of a chrysalis of the Mourning Cloak butterfly Nymphalis antiopa (Linnaeus, 1758), also snapped last weekend. The top one is from my point-and-shoot Lumix DMC FZ28 with its OK macro and terrible flash. I was trying to follow Alex Wild's maxim and make the best of its limited features. I think I did okay, but the viewer will be the judge.
Chrysalis of Nymphalis antiopa (Linnaeus, 1758) Mourning Cloak
The second shot is my wife's Nikon D70 in action. Both shots were difficult and involved lying on the ground and shooting up under the runners of a cabin, but the latter is the better image for documentation, especially in its full size (cropped to the essentials) 11.2 mb vs the Lumix 2.84 mb. However, to-date, neither camera nor photographer has been able to capture a decent image of the too flighty adult Mourning Cloak.

Friday, August 3, 2012

I just want to bee ... left alone

Newly emerged Bombus moderatus looking for a night's rest in a daisy
Bug Girl tells me that my idea of a post defending Spiderman's wrist-spinning abilities based on what we know about hox genes and what we don't know about radioactive spider venom would be a traffic fatality. Well, the Home Bug Garden has never been about high traffic, just musing about urban biodiversity and trying to stay sane in Zone 3, but maybe I'm getting too serious. Ergo, a new (and probably ephemeral) series for those of us who just want to bee left alone.
Some day maybe she'll be a queen, but it's a long time until next May
And who better to kick off the series, then our very own recent colonist Bombus moderatus (or is it cryptarum? Only the genes know for sure). This newly emerged adult female showed up the other night in the cool evening between storms looking for a place to sleep. It's nearing the end of summer in Zone 3 and the successful bumble bee colonies are producing mostly reproductives: males (drones) and females (next year's queens). A few workers continue their job of collecting pollen and nectar, but most of the bumble bees you see at flowers from now until frost will be drones. Now and then you may find a large and brightly coloured queen wannabe. She'll have to load up on carbos and find a place to outlast predators, parasites, and the long cold winter. If she survives until May, then she has a chance to found her own colony and be a queen, but right now she can only dream.
To sleep, perchance to dream ...