Saturday, April 23, 2016

What's on Dat Scat?

My last post addressed what kinds of insects can be found in dung, but today I want to show you what can be found on animal poop. While blow flies, family Calliphoridae, are often overwhelmingly abundant on fresh manure, you'd be surprised what else comes in for a taste.

Acmon Blue and Reakirt's Blue enjoying some refreshing scat with broad-headed bugs

Would you believe many butterflies will visit scat? Last year I happened upon this scene on a concrete nature trail in a popular park here in Colorado Springs. There were two species of gossamer-winged butterflies imbibing from some kind of predator poo. The ones with the orange bands on both the front wings and hind wings are Melissa Blues. The one with orange on the hind wing only is an Acmon Blue. The other one, without orange bands, is a Reakirt's Blue.

Melissa Blue joins Reakirt's Blue and broad-headed bugs

Males of many butterflies require mineral supplements that they can pass along to females during mating. Dung is one such mineral-rich resource.

Some butterflies feed mostly on dung, or carrion, and hardly ever visit flowers. Among them are the satyrs like this Northern Pearly-eye that was visiting dung on a bike trail in a suburb of Chicago, Illinois.

Northern Pearly-eye butterfly

The Red-spotted Purple is also notorious for preferring dung and corpses for nourishment, though one usually sees the territorial males perching on the ground or up on leaves in the canopy along stream or river corridors, or forest edges.

Red-spotted Purple butterfly

Other surprising visitors to scat are true bugs that normally feed on ripening seeds or other plant material. Finding so many broad-headed bugs, family Alydidae, sharing the poo-pile with the butterflies was quite surprising. There are at least two species here: Megalotomus quinquespinosus is the brown one, known as the "Lupine Bug." The other, smaller and blacker, is a species in the genus Alydus.

Male Golden Dung Fly

Different kind of excrement seems to attract different kinds of insects, at least to a degree. Fresh cow and horse dung is a favorite breeding ground for dung flies in the family Scathophagidae. The males stake out pats of poo and defend them from other males, while also intercepting females receptive to mating. The female lays her eggs in the manure and the larvae that hatch feed and develop there. You can easily recognize males of the Golden Dung Fly, Scathophaga stercoraria, but their fuzzy, bright golden appearance.

Various blow flies on what is probably bear scat

The blow flies (Calliphoridae) come in two basic varieties: "greenbottles" that are wholly metallic green, mostly in the genus Lucilia, and "bluebottes" that are usually larger, and gray with a metallic blue abdomen. Most of the common bluebottles are in the genus Calliphora. There is also the Black Blow Fly, Phormia regina, that is black or deep metallic blue-black. All can be present at dung.

Black scavenger fly

Tiny and wasp-waisted, black scavenger flies in the family Sepsidae are not easy to see immediately given their size, but their behavior is unmistakable: they walk around "rowing" their wings as if they needed the extra propulsion to get around.

Flesh flies of the family Sarcophagidae are gray with black "pinstripes" on the thorax, and usually red eyes and a red "tail." They are about the size of the blow flies, though some are smaller. The females "larviposit." That is, they lay tiny maggots in dung or carrion, rather than laying eggs. Bypassing the egg stage gives them a head start in exploiting the food resource.

A mating pair of flesh flies

Dung-watching is probably not going to become the next big thing in the world of naturalists, but if you can get over the "yuck factor," you might find some interesting creatures among the clean-up crew. Just make sure you are up wind.

1 comment:

  1. Amazing photos, it's so rare to be able to see creatures up close!

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