Hepatica has finally opened its hairy buds and greeted the world with its beautiful white, pink, blue and lavender blossoms. Typically the only wildflowers to appear earlier than this member of the Buttercup family are skunk cabbage and coltsfoot. Like many flowers, hepatica blossoms open on sunny days, and close at night and on cloudy days. This prevents rain from washing out the pollen and nectar which help attract pollinating insects, including early-flying bees and flies.
It’s hard to believe that flies are not only active but mating now, given the snow and low temperatures that Vermont is still experiencing, but these two flies were perched atop coyote scat doing just that. They are in the Heleomyzidae family, whose members are often found in dark or cold places, and are most likely to be encountered in the spring or late fall. There are species associated with caves, mammal burrows, carrion and birds’ nests, in addition to scat.
Galls are abnormal plant growths that can be caused by insects, fungi, bacteria, nematode worms and mites. Insects cause the greatest number of galls and induce the greatest variety of structures. Galls provide both food and shelter for the organisms living within them. Galls develop during the growing season, often in buds and on leaves. Pine Cone Willow Galls, named for their resemblance to small pine cones, are found on willows, typically in terminal buds. A gall midge (Rhabdophaga strobiloides) is responsible for the willow bud going haywire and developing abnormally. (No-one has determined exactly how insects cause galls, whether it’s the act of laying eggs in or on the plant, or if it’s somehow connected to the chewing of the larvae into the plant.) Each gall-making insect has a specific host plant, or small group of related plant. The galls that each insect species induces and lives in while developing into an adult has a recognizable shape and size. When you think you’re seeing pines cones on willow trees, you’re not hallucinating, you’ve just discovered the temporary home and food supply of a tiny fly, known as a midge.
White-tailed Deer fawns are close to two months old now, and will retain their spots until their gray winter coat grows in this fall. The dappling of the spots enhances a fawn’s ability to remain camouflaged up until it is large enough and strong enough to outrun most predators. However, it doesn’t hide them from biting insects. During the summer months, when White-tailed Deer, including fawns, have a relatively thin, cool coat of hair, they are very vulnerable to biting insects such as female horse flies and deer flies. These flies make tiny slices with their blade-like mouthparts in their host’s skin in order to have access to their blood. This fawn was being constantly bothered by such flies.
It always comes as a surprise to see tiny creatures moving nimbly over the surface of the snow. However, there are quite a few insects and spiders that do, thanks to the glycerol that they produce in their body fluids that keep them from freezing. The Snow Fly (Chionea sp.) is wingless, probably because at sub-freezing temperatures, it would be very hard to generate enough energy for maintaining flight muscles. They (along with other flies, mosquitoes and gnats) do have two vestigial wings called halteres, the little knobs on the fly’s thorax. They inform true flies about the rotation of their body during flight, and are thought to act as sensory organs for the flightless Snow Flies. Throughout most of the year Snow Flies can be found in leaf litter, but come winter the adults emerge, mate and lay up to 200 eggs. The lack of predators such as dragonflies and most insect-eating birds makes winter a relatively safe time for Snow Flies to be out and about. Their life span is about two months, during which time they drink by pressing their proboscis against the snow, but don’t eat. (Snow Fly in photograph is a female, measuring less than ½”.)
Earlier this week, when temperatures were in the 40’s and the sun was shining in the late afternoon, there were clusters of male winter crane flies (Trichocera sp.) hovering two or three feet above the snow, bobbing up and down as they did their mating dance. Females are on the surface of the snow most of the time, but join a swarm in order to find a mate. Winter crane flies are active throughout the winter, as their name implies, and are a source of food for resident songbirds. The larvae feed on decaying vegetation, and can be found in leaf litter, shelf fungi and compost heaps.
12-3-11 Larvae-seeking Downy Woodpeckers
Robber flies have been covered in a previous posting, but their beak, or proboscis, deserves its own post, in my opinion. These predators perch and scan the sky for prey. When they see it they anticipate the prey’s direction and speed of flight and fly out and intercept it mid-air. Their objective is to paralyze the prey and liquify its insides so that the fly can drink it. The tip of the robber fly’s beak is covered with microscopic stiff bristles, designed to secure it within the wound it creates. Once this is achieved, a dagger-like shaft hidden inside the beak is used to stab its victim in the head or thorax and inject the paralyzing neurotoxic and digestive enzymes. The resulting fluid is sucked up by the fly’s beak, or proboscis.
If you want to get an idea of the number and variety of wasps, bees, beetles and bugs that reside in your area, go to the nearest goldenrod patch sit for a spell – this member of the Aster family is a magnet for insects. You’ll find many foliage- eating bugs and beetles, leaf-mining larvae, nectar and pollen feeders, and flower and seed-eaters. In addition, many predatory spiders (jumping and crab, especially) and insects (ambush bugs, ladybug beetles, flower bugs etc.) have discovered that goldenrod is a goldmine for them, as well. Researchers have found nearly 250 species of insects feeding on one species of goldenrod (Solidago canadensis). Pictured from left to right are a long-horned beetle (locust borer, Megacyllene robiniae - pollen eater), a fly (nectar feeder) and bee (nectar and pollen feeder).
Robber flies often perch on the leaves or stems of low plants waiting until suitable prey flies by, and then attack it in the air. They have long, strong, spiny legs for grabbing prey, and piercing-sucking mouthparts for consuming it. Robber flies prey on a variety of insects, including bees, beetles, bugs, dragonflies, grasshoppers, flies, leafhoppers and wasps. Once they capture an insect, they pierce it with their short, strong proboscis, or mouthpart, and inject their saliva into it. The saliva of robber flies contains enzymes that paralyze the insect and digest its insides, which the robber fly then drinks. The pictured robber fly is feasting on the innards of a stink bug it just captured.