urbpan: (dandelion)
 photo IMGP3623_zpsflg8ywqh.jpg
Every growth, marking, bump, or blemish on a plant was made by something, and surprisingly often the cause can be closely traced to a particular animal. I could see from a distance that these hickory leaves had orangish spots on their underside.

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On close examination the spots were furry balls! These little growths are galls that have grown around insect eggs, in a weird bit of mostly harmless and stunningly common parasitization.

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These orange tribbles hide and protect the larvae of the hickory gall midge (Caryomyia sp.). The creature inside is a helpless pinpoint of a maggot that will grow into a fly so small that it would otherwise go completely unnoticed by humans.
urbpan: (dandelion)
 photo P1070359_zpsxuap3dq7.jpg
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
urbpan: (Default)

Mating swarms of non-biting midges drift in the mid-day air on an unusually warm December day in Hartford. River birches frame the photo. Photo by [livejournal.com profile] urbpan. Location: The Riverwalk, Hartford, Connecticut.

Urban species #347: Non-biting midge Family: Chironomidae

A column of insects gathers in the air, slowly drifting, sometimes toward a light source, sometimes toward an object such as a passing human. The column may be a small vertical puff of a few feet, or a towering nimbus hovering from face level up to thirty feet tall. If you are like me, you swish your hat through the cloud to catch one or two of these tiny flyers, to see what they are. You may be alarmed to see what looks like a mosquito! But if they were all mosquitoes you would be covered with bites by now. Midges can be told from mosquitoes by the lack of scales on their wings, different mouthparts, and by the fact that their front pair of legs is their longest. The cloud moves on, perhaps leaving one or two tiny flies in your hair or, if you were riding through on your bike, your eye.

The insects are midges, specifically "non-biting" or "chironomid" midges. (They are called non-biting midges to distinguish them from small biting flies such as no-see-ums, which are sometimes called midges.) The columns are mating swarms, and the vast majority of the midges in the swarms are the males. Male midges (and males of mosquitoes and moths) can be recognized by their plumose, or featherlike antennae. These are surface-area maximizing structures which catch scent molecules and draw the males to their purpose.

Midges are almost always found near fresh water, where they live as larvae. Midge larvae are among the most abundant and important aquatic invertebrates. They are food for other insects, as well as young fish and amphibians. Astute ecologists can determine a great deal about a body of water by the midges that live in it. Each species can tolerate different levels of different pollutants, as well as different pH levels, temperatures, levels of oxygenation and so on.

Adult midges, though tiny, can be important food for birds and bats. Swallows and swifts are drawn to bodies of water to catch the adults as soon as they emerge from their aquatic pupae. One imagines that this swarm of midges photographed at the bank of the Connecticut River in December has an adaptive advantage: by engaging in the mating swarm in winter, they have thwarted their bird, bat, and dragonfly predators, who have migrated or are hibernating.


A male midge swept out of its swarm with my hat.

Thanks for identification help from [livejournal.com profile] rockbalancer!
also [livejournal.com profile] nutmeg and [livejournal.com profile] phlogiston_5

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