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Diptera

Robber Flies Capturing Prey

8-3-16  robber fly 009The robber fly family, Asilidae, is one of the largest families of flies.  All robber flies are predaceous and are recognized by their long bodies, forward-facing beaks and a tuft of hairs above the beak.  You find them on the ground or on leaf tips and other sunny spots where they survey the area for flying insects.  Once a robber fly has spotted a suitably-sized prey, it darts out and impales it with its stout beak.  It then inserts its needlelike “tongue” into the prey’s neck, eye or other weak spot, immobilizing the insect and liquefying its innards with an injection of saliva that contains nerve poisons and enzymes that break down proteins. Finally, it drinks its meal.  Pictured is a species of robber fly in the genus Diogmites, whose members are known for dangling by a foreleg while dining.

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Hover Fly Mimics Bald-faced Hornet

8-5-15 bald-faced hornet and hover flyAdult hover flies, often referred to as syrphid (family Syrphidae) or flower flies, feed on pollen and nectar, and are often seen hovering at or crawling on flowers. Many have black and yellow bands on their abdomen, and are frequently mistaken for bees. There are certain species of hover flies that mimic stinging wasps, including yellow jackets and bald-faced hornets (see photo). Predators such as birds, ambush bugs, and spiders might think twice about eating an insect that can sting, and hover flies take advantage of this. The process through which this occurs is called Batesian mimicry, and refers to when a harmless species evolves to imitate a harmful species that has the some of the same predators.

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Robber Fly Mimics Bumblebee

8-4-14  robber fly like bumblebee2 054Milkweed leaves make excellent platforms for all kinds of insects, particularly those such as dragonflies and robber flies, which sit, wait and watch, surveying the landscape for prey to ambush. This robber fly could quite easily be mistaken for a bumblebee. However, the short, straight antennae and the presence of only two wings (instead of four) tell you it’s in the order Diptera (true flies). The pointed, stout proboscis, bearded face, fleshy feet and long, tapering abdomen narrow it down to a species of robber fly. Robber flies in the genus Laphria resemble bumblebees – they are typically quite hairy, with black bodies and yellow stripes on their abdomens. Like other species of robber flies, they hunt by perching and snagging prey such as other robber flies, bees, wasps or beetles. They often return to their perch, inject the prey with enzymes that dissolve its innards, and then have a long drink. Why mimic a bumblebee? To deceive unsuspecting honeybees, wasps and other insects that would make a good meal.

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Willow Beaked-Gall Midge

10-30-13 willow beaked-gall midge   047Now that most of the leaves have fallen, it’s a good time to look for galls that form on woody plants. Willows are host to a great number of gall-making insects, including tiny flies called midges. The most common species of willow gall midge is the Willow Beaked-Gall Midge, Rabdophaga rididae. In the spring, after mating, the adult female midge lays an egg in a willow bud (often terminal) that is just starting to expand. The egg soon hatches and the larva burrows deeper into the bud, which causes the bud tissue to swell and form a gall, usually with a “beak” at the top. The larva remains inside the gall through the winter, where it has a constant supply of food (the interior of the gall) and shelter. In the spring the larva pupates, and an adult midge emerges and begins the cycle all over again. Some gall midges are crop pests, but willows are not significantly damaged by the Willow Beaked-Ball Midge.

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Jewelweed Gall Midges

10-4-13 jewelweed gall  277Abnormal plant growths called galls come in all sizes and shapes, are found on leaves, buds and stems, and are caused by a number of agents, including insects. A majority of insect galls are caused by the eggs and developing larvae of flies, wasps and midges. Jewelweed, or Touch-Me-Not (Impatiens capensis), has a very distinctive looking aborted bud gall that is produced by a midge (Schizomyia impatientis). While some galls provide shelter and food for a lone resident, the Jewelweed Gall Midge is colonial, and several orange larvae can be found residing in separate cavities within the gall. These midge larvae are now emerging and will overwinter as adults.

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Chicory Pollinators

7-19-13 chicory pollenTwenty minutes of observing air-borne visitors to a patch of roadside Chicory revealed nine different species of pollinators, including bees, flies and beetles. Most of the insects were bees, which makes sense, as honeybees, leafcutting bees and ground-nesting bees are the primary pollinators of this flower. Without exception, all of the pollinating insects were covered from head to toe with Chicory’s white pollen grains. As they circled the flowers’ stamens collecting pollen, the insects’ bodies were inadvertently dusted with some of it. Thanks to these diligent pollen-collectors and transporters, American Goldfinches and other seed-eating birds will be feeding on Chicory seeds come winter. (Electron microscopy by Igor Siwanowic and Scienceworks.)


Stinky Squid Fungus

7-16-13  Pseudocolus fusiformis 225There is no way you can walk by the fruiting body of Pseudocolus fusiformis, a member of the Stinkhorn family Phallaceae, without noticing it. Its shape is markedly different from most fungi, in that it has three or four separate orange “arms” which are fused at the top. If your eyes don’t detect it, your nose most certainly will. Also known as “Stinky Squid,” this fungus emits a strong, putrid odor which comes from the dark green, spore-bearing slimy material (gleba) that is found on the inner surfaces of the arms. This smell attracts insects, primarily flies, which inadvertently disperse spores after visiting the fungus. Look for round egg-like whitish structures at the base of Pseudocolus fusimormis – these are young fruiting bodies that have yet to develop arms. (Thanks to Shiela Swett for photo op.)