Flies for Thanksgiving

A pair of Leafminers (Liriomyza sp.) celebrate Spring in the Home Bug Garden

Thanksgiving is a time for giving thanks for many things; but historically, a good harvest has to rank near the top. In the Home Bug Garden the harvest is what the hail, drought, floods, frost, slugs, pathogens, birds, and bugs have left for us to eat. Of all of these kleptoparasites and vagaries of the weather, the bugs steal the least. The caterpillars of the Cabbage White Butterfly devastate my kohlrabi and kale. Flea beetles and root worms prevent me from growing broccoli, turnips, and radishes. Leaf miners make chard, beets, and spinach unprofitable use of limited space. But most other insect 'pests' don't do enough damage to make a difference. I suppose that is one advantage of gardening in the cold, short growing seasons of Zone 3.

House Sparrows do more damage to peas in the HBG than leafminers

The pair of mating flies at the top may be one of those minor HBG pests, perhaps the same fly that makes leaf mines in my peas. But unless I use row covers, the House Sparrows eat most of the young peas leaves, so pea leaf-miners are rather rare and more interesting than pesky. These particular Leaf-mining Flies (Agromyzidae) belong to the very large genus Liriomyza which contains many of the important agricultural pests. The family itself is very successful - the third largest family of acalyptrate flies according to another of my reasons for giving thanks today: a new book by Steve Marshall: Flies, the Natural History and Diversity of Diptera (2012, Firefly Books) and the time to peruse it. And not just agromyzids, but 10 other families of Diptera have maggots that munch through the middle cell layers of leaves.

Lauxania shewelli Pérusse & Wheeler, 2000

Maggots munch dead leaves to, as demonstrated by another highly successful family of acalyptrates (i.e. 'higher' Diptera with an organ called a ptilinum but without calypters) the Lauxaniidae. Like many Diptera, the larvae of Lauxania shewelli Pérusse and Wheeler, 2000, feed on decaying matter. I'm not sure exactly what detritus Lauxania maggots feed on, this is often the case when a fly has not come under close scrutiny for eating us or our livestock or our plants, but many lauxaniid maggots have the interesting habit of mining dead leaves. Adults scrape spores and mycelia of fungi from live leaves (Marshall 2012), probably what is going on in the picture above. As Steve Marshall points out, adult flies are not known for eating leaves - they seem to never have managed that evolutionary leap.

Scathophaga cf stercoraria (Linnaeus, 1758) predator as adult, saprophage as maggot

So we have numerous maggots that find leaves, dead or alive, perfectly acceptable as food, but no adult flies with the ability to eat vegetation. I find that curious. Many flies, like the Golden Dung Fly Scathophaga cf stercoraria (Linnaeus, 1758) above, are predators of insects that piece and suck their haemolymph. Far too many flies have the ability to suck our blood. But adult flies don't eat leaves or suck the sap of plants, unless it is oozing from a wound. I guess that is something else to give thanks for.

Lecanocerus compressiceps Borgmeier, 1962

Well, there is the caveat that we don't actually know what all that many flies do. Take the Scuttle Fly (Phoridae) above, Lecanocerus compressiceps Borgmeier, 1962. Unfortunately, the common name 'Antler Fly' is already taken by some fascinating little flies that feed only on the discarded antlers of moose and deer and a strange fruit fly from New Guinea. The generic name 'Lecano-cerus' seems to mean 'plate-horn', which is descriptive, but hardly evocative. I'm sure these male ornaments are used for something interesting, but google and Marshall both fail when it comes to explaining just what. Yet another mysterious fly! Well, nothing so interesting seems to be on the wing at the moment and I'd better do something with all those harvested tomatoes before they turn into dew-loving flies. So Happy Thanksgiving to all my Canadian readers!

A plate-horn to the genus author, but an Albertan Antler Fly to me

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 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