The Urban Pantheist

Looking like a wasp is an adaptation assumed by many different species of flies. Looking like a really huge wasp is more rare, but this Mydas fly Mydas clavatus has it down. It has a wasplike flight and measures a full inch in length, making it one of the largest true flies around. Its larvae feed on beetle grubs in the soil, and adults visit flowers for nectar. It may look scary but its one of the most beneficial insects in the yard.

A calliphorid fly (bottle fly) warms up on a leaf.


The reproductive parts of a daylily beckon luridly.


Japanese honeysuckle ready for a chance encounter with a hummingbird.


A tiny grasshopper nymph (subadult that hasn't molted into a winged adult) just hours or days old, ready to eat soft tender vegetation.

Weird growths on plants have always been fascinating to me. I was so happy when I learned that most of them are caused by animals! In this case, a very small fly--a midge called Polystepha pilulae*--laid her eggs in the flesh of this oak leaf. The tiny maggots hatched and began feeding, and the flesh of the leaf hardened around them, protecting them as they ate. Unless they were parasitized by a wasp, they will pupate in their galls and emerge as more tiny long-legged midges.


*Many crowned ball-maker

These black midge-like flies were hovering all around the wet woods we were walking in northern Vermont. I swatted one out of the air with my hat--my favorite flying insect catch method, as it usually stuns but does not injure the insect. Getting a better look at the fly showed me that it wasn't a midge, but looked more like a March fly. But it was October.

March flies get that name because they suddenly appear in great numbers in early spring. The males hover in swarms over the places where the females emerge in anticipation of mating. A few species of "March flies" instead emerge in autumn, including the male fly pictured here Bibio slossonae.*



*Bibio is a Latin word that suggests an insect that is generated by wine--perhaps more fitting for Drosophila. The species name is in honor of entomologist Annie Trumbull Slosson.

The flesh flies (family Sarcophagidae*) are a fairly distinctive group of true flies associated with dead animals. Many, but not all, place their young on carcasses to eat the decaying flesh--flies in this group are useful for forensics. Other Sarcophagid maggots are parasitic on other invertebrates, and at least one specializes on the nests of turtles. All are placed directly at their food source by a female who has carried her eggs inside her until they hatch. Adults might snack on the juices of the dead, but also like sweet treats like flower nectar and aphid honeydew.


*Flesh eating family

When someone asks, as they always eventually do, "why do mosquitoes exist?," they're really asking another hidden question. Because mosquitoes exist for the same reason all organisms exist: evolution provided adaptations to fit the available energy sources. Blood-suckers suck blood because blood is a liquid that can be sucked--the alternative is flesh-eating. Which is worse?

The hidden question is this "Is the natural world in balance?" The answer of course is no. Humans have proved to be so adaptable in such a short time, that we have thrown the entirety of the rest of the natural world out of kilter. We have spread to every corner of the globe, bringing our food animals with us. We have created vast climate-controlled structures to live in. We have dug deep into the earth to find energy trapped in hydrocarbons that have held onto it for millions of years, and released so much carbon dioxide into the atmosphere that we have changed the atmosphere and climate of the planet forever.

One of the most mundane activities of humans--the selling of goods between one land mass and another--has resulted in the spread of mosquitoes. In prehistory the mosquitoes would have lived in balance with their predators--the mosquitoes pushing their hosts gently toward fitness, the predators keeping them at a tolerable level. Moving mosquitoes around the world has brought these biting flies to land masses that never had them before, and brought multiple species to places that used to have only a few species. The shiploads of tires and other mosquito-moving industries did not bring along the predators of the mosquitoes. We ask too much of our native bats and dragonflies--there are simply too many exotic mosquitoes for natural controls to retake the balance.

The result is blood-borne diseases in North America bearing the names of regions in Africa. The result is the almost complete destruction of Hawaain bird diversity. The result is mosquitoes that bite in the daytime, that breed in dumpsters and dirty gutters, in densities that mock the equilibrium of the past. Why are there mosquitoes? Because there is blood to drink. Why are there so many god damned mosquitoes? Because human activity creates and destroys habitat in a way that rarely makes the world a better place.

Mosquito=little fly
Mosquito family Culicidae=family of little flies

I first noticed these very small (less than a mm long) flies when I was at work softball games. It turns out that sitting in a grassy field in summer is surefire way to encounter them. You increase your chances if you bring a dog with you, as the flies are drawn toward the mouth, ears, eyes, and anus of your companion. These are Chloropidae*, variously called frit flies, grass flies, or tellingly, eye gnats. Their larvae feed in the stems of grasses, while the adults seem to slake their thirst on sweat, tears, and other vertebrate bodily fluids. Some species, I am alarmed to report, are known to be vectors of conjunctivitis.


* "green eyed family"

What you see here, infesting our kitchen compost container, is one of the most important animals in human history. The humble red-eyed fruit fly is a tiny pest found worldwide. Its maggots feed on the yeasts that feed on fruit sugars--so anywhere a banana is ripening, or a glass of wine has sat out too long, or some juice was left in a discarded, you will find these vinegar flies circling. Because they are easy to rear in captivity, and reproduce incredibly quickly, they are among the most frequently used lab animals. It is impossible to overstate the contribution this species has made to science.

They have been used in so many papers and studies, that even though their classification has changed--they are no longer taxonomically Drosophila melanogaster*, they are Sophophora**--that their old scientific name is still used. Nobody wants to go through the hundreds of thousands of uses of Drosophila and find and replace them with Sophophora.

* "Dew-loving, black belly"

** "Carrier of wisdom"

At half a centimeter long, and more agile than almost any flying animal alive, it's hard to think that this fly needs its silly bee costume. But that warning coloration is so effective that even completely harmless and difficult to catch creatures like this Toxomerus marginatus* flower fly dress in yellow and black stripes. This tiny pollinator can hover (they are also called hover flies), fly in any direction including backwards, and males engage in fun territorial battles. Females lay eggs that hatch into legless monsters that roam your garden and destroy aphids.

* Toxomerus, from Greek toxon 'bow' + meron 'thigh' (refers to the bow-shaped hind femur); marginatus, referring to the yellow margin on the abdomen.

When I talk about living things (which I do kind of a lot, even in real life), one of the themes I return to is this: The vast majority of living things are not beneficial to humans nor are they harmful, they simply are. Especially with insects, people want to assign every one of them to either the good guy side or the bad guy side. The insects do not choose sides. They become more abundant when we provide more habitat for them, they become less abundant when we destroy their habitat, like all living things. This picture-winged fly Delphinia picta* does no harm to us, and provides no great service to us. I think it looks really cool (especially when better photographers get ahold of it) with it's long snoot and decorated wings. Its larvae feed on compost and compost-like materials, arguably helping gardens become more fertile. But mostly this species goes about its business of replicating itself, as it has for many millions of years before humans came along to decide if it was good or bad.

* "Painted dolphin"