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

Frog spit & colour morphs: Pseudodiversity & other false ideas

Frog spit and spittlebugs are one of those childhood memories that now evoke mixed feelings. Did I really eagerly plunge finger tips into poop and plant-sap spittle and react with joy when uncovering a frothing froghopper nymph?

Well, that’s how I remember it, but now things are different. Spittlebugs (true bugs: Order Hemiptera, Family Cercopidae) or froghoppers (as the adults are called) are interesting insects for any number of reasons. One of the primary is, of course, the protective envelope of bubbles that the nymphs generate around them as they feed. That’s cool, even if you aren’t a kid, but once you know that the bug anus is intimately involved, one is apt to get a bit skittish (NB – always wash your hands after playing with spittlebugs). Adult fastidiousness aside, the most likely spittlebug one is apt to encounter is two things you don’t want in a garden bug: polyphagous and exotic. Another way to say this is ‘an alien that eats everything’.

Summer before this, we had quite the explosion of just such a spitting machine in the Home Bug Garden: Meadow Spittlebugs (Philaenus spumarius). Bellflowers, globe flowers, Queen-of-the-Prairie, goldenrod, aster, yarrow, and many other cherished garden gems had hunks of spit sitting just below the flower buds – wilting the buds and terminating the flowers. Hundreds of soapy squirts and weeks of spit and green ocher stained finger tips later, the spit population appeared undiminished. It was enough to drive a knee-jerk environmentalist to the evils of synthetic insecticides – if only such a synthetic chemical alternative were available! Alas a history of insecticide abuse, and the inability of government to favour science over fervour, has left the home gardener with little to do other than pray for parasitoids. Unfortunately, spit and parasitoids don’t seem to mix.

Not that I am entirely the innocent victim in this outbreak. I suspect the main reason for our spit-drenched garden was that I left most of my perennial plant stems standing over winter. I could claim that I did this for aesthetic reasons (winter interest), horticultural reasons (plant tops trap snow and help plants to overwinter), or just plain knee-jerk environmentalism (it is natural for plant tops to last over the winter and cutting them down would be unnatural and wrong). Truth be told, being a lazy bugger (aka ‘overworked’) conspired with all of the before to let the tops stand. Unfortunately, it is inside the stems of perennial plants that the froghopper secrete their eggs – the eggs that turn into spit and dead flowers the next Spring.

This last year I cut down and composted my perennial tops before Spring had sprung. Leaving them up most of the winter looked good and trapped snow, and cutting them down before it got warm seems to have kept the spittlebugs down to squishable levels. Other insect pests and diseases also overwinter in plant tops, so ‘better late than never’ applies here. The only downside to this approach is that fewer spittlebugs means even fewer froghoppers – and the Meadow ‘Froghopper’ is a really interesting animal, if only because it looks like dozens of different species.

Bugguide Net has a great poster displaying some of the diversity of colour morphs found in this single species and this posting displays a few of the variants found in the HBG. It is a bit disappointing that we have so few froghopper species (only two, including the unidentified spittlebug on our birch), but the Meadow Spittlebug is a good reminder of the pitfalls of using skin colour as a guide in life. No matter what the colour on the surface, a miscreant may lie below.