Howdy, BugFans,<\/p>\n
A Bug Story in Three Acts.<\/p>\n
As the BugLady was walking through the woods at the Ozaukee Washington Land Trust Huiras Lake property in late spring, she kept scaring up skittish little \u201cwasps\u201d that hop-scotched from shrub to shrub ahead of her. When she finally caught up with them (too briefly), she found not wasps, but flies in the wasp\/bee-mimicking syrphid\/flower\/hover fly family Syrphidae.<\/p>\n
\u00a0 [metaslider id=466]<\/p>\n Syrphid larvae occur in a variety of habitats, including aquatic. While some species are scavengers, feeding on rotting organic materials (even within ant nests), others (despite the fact that syrphid larvae are headless and legless) are carnivores, acting as beneficial biological controls on aphids, leafhoppers, and other pest insects. The most famous syrphid is the Rat-tailed Maggot<\/a>, the aquatic larva of the drone fly Eristalis tenax<\/em>, which lives in shallow, murky water, breathing, as both larva and pupa, via a long respiratory \u201ctail\u201d that projects from its posterior and stretches up through the water\u2019s surface film (the tail has earned them the nickname mousies<\/em>).\u00a0One source noted that some larvae use those tubes to puncture reed stems underwater and tap into the air chambers within the stem.<\/p>\n \u00a0 Temnostomas are territorial and will attempt to chase larger insects. Males hang out near flowers, waiting for females; the females multitask, flying from flower to flower, feeding as they mate, with the males in tow.<\/p>\n Their larvae are saprophagous<\/em>, living and feeding within decaying wood and possibly spending two winters as larvae. A report on saproxylic flies of old growth forests of Finland and Russia describe the larvae as having \u201chuge hooks on the [barrel-shaped] thorax with which they tunnel into firm sapwood of fallen trees and branches.\u201d<\/p>\n \u00a0 Temnostoma is, at first glance, a wasp mimic, probably of the mason wasps (picture included). Look twice and you note that Temnostoma has two wings to a wasp\u2019s four, and its antennae are short.\u00a0But some syrphids don\u2019t stop with appearance, they mimic wasp behavior, too—raising their dark-colored, front legs so they look like long antennae (a feature that\u2019s apparently important to discriminating birds) (some syrphids do have long antennae, and they don\u2019t do the leg-raising behavior), mock-stinging when handled, wing-wagging, eschewing the direct flight of syrphids for a wasp\u2019s erratic patterns, and even holding their wings out in a wasp-like \u201cV\u201d at rest.<\/p>\n [metaslider id=468]<\/p>\n Have scientists studied this? Indeed, they have! The syrphids\u2019 ploy falls in the category of Batesian mimicry, in which a harmless\/palatable organism protects itself by disguising as a harmful one. A mimic may not only look, but may also sound, smell, and\/or behave like its model. Adding behavioral prompts to a good visual resemblance seems like a no-brainer, but in a study of 57 syrphid species, Carleton College researchers found that behavioral copycats were not that common (only 6 of their test species, three of them Temnostoma<\/em>, practiced behavioral mimicry). They questioned whether a poor visual match might be overcome by a good set of behaviors.<\/p>\n What did they find?<\/p>\n In a blog entry entitled \u201cGood mimics have the costumes and the acting skills,\u201d one of the co-authors includes two, nice videos of the flies in action: Katatrepsis—Good mimics have the costumes and the acting skills<\/a>.<\/p>\n The Eye of the Beholder?<\/strong> Another research team attempted to evaluate wasp-mimicking syrphids through the eyes of a pigeon (with a nod to the fact that pigeons do not prey on syrphid flies). After pigeons were trained to recognize (peck at) images of wasps and images of non-mimetic flies, images of syrphid flies were added, with the various morphological features simplified and optimized.<\/p>\n What did the pigeons tell them?<\/p>\n
\nIt\u2019s a large and widespread fly family whose members range from small-and-delicate to large-and-clunky honeybee mimics called drone flies. Adults feed on nectar and pollen, mostly from yellow or white flowers, and on aphid \u201choneydew,\u201d and they\u2019re considered important pollinators despite the fact that they\u2019re not designed to carry as much pollen as either wild bees or honeybees can. Overall, they\u2019re exquisite, and good for your garden (unless their larvae are among those that eat flower bulbs). While they are excellent flyers, adult syrphids tend to be homebodies, not straying far from good larval habitat. Intriguing side note—according to Wikipedia<\/em>, \u201cThe orchid species Epipactis veratrifolia<\/em> mimics alarm pheromones of aphids to attract hoverflies for pollination.\u201d<\/p>\nAct II \u2013 Meanwhile, back at Huiras Lake<\/h3>\n
\nSo, the small bees turned out to be syrphid flies in the genus Temnostoma<\/em> (from the Greek words temno<\/em> and soma<\/em>—cut body).\u00a0There are only 10 Temnostoma<\/em> species in North America, but the BugLady\u2019s not going to venture past genus on this one—four, look-alike species live in the northeastern quadrat of North America.\u00a0A European key to the genus described them as dwelling in \u201chumid deciduous forests, where they bask on leaves and twigs and visit flowers of understory herbs.\u201d\u00a0Check.<\/p>\nAct III – The Scientific Principle du jour \u2013 Mimicry:<\/h3>\n
\nJust how good does a mimic have to be, anyway (subtitle—is it more important that the guy who plays Jimmy Hoffa in the movie look like Hoffa, or act like Hoffa?)?<\/p>\n\n