The Carlisle Mosquito Online

Friday, May 28, 2010


Fishfly and Thick-headed Fly

“The more clearly we can focus our attention on the wonders and realities of the universe about us, the less taste we shall have for destruction.” Rachel Carson

Thick-headed Fly. (Photo by Kay Fairweather)

Rachel Carson was born 103 years ago, on May 27, 1907. Her book Silent Spring, published in 1962, changed the way we think about the environment and raised awareness of bioaccumulation of poisons. It led, eventually, to regulations against the use of DDT. Today we have many more pesticides but the Environmental Protection Agency approves them before they are released for use. Good idea, but who says the agency is not cut from the same cloth as the overseers of the financial industry? Many insects (and other creatures) would have been wiped out if the widespread spraying of DDT had continued so I have chosen to commemorate the week of Carson’s birthday with a tale of two flies. They are not representative of the best of flies or the worst of flies but each has its own story.

Flies tend not to engender spontaneous feelings of joy (probably the legacy from some of their disease-spreading bloodsucking relatives) and yet if you can discover the name of a fly you can then find out its story and add the creature to your realm of known wonders of the universe about you. It is no longer just another “fly”, and as Carson suggests it may lead to less taste for destruction.

Fishfly and her (doomed) larvae. (Photo by Robin Weiss)

The naming of flies: True flies belong to the order Diptera, a name from the Greek meaning two wings. Where another insect would have its second pair of wings, Dipterans have a pair of knobby organs called halteres which function as gyroscopic aids for flight control. The common name of a true fly does not always include the word “fly” and to complicate matters, some insects from other orders are called flies. The convention for common names is that with true flies the word “fly” is kept as a separate word – as in Thick-headed Fly. For members of other orders “fly” is added as a suffix as in Firefly, Butterfly or Dragonfly. These insects, along with the Fishfly, all have four wings.

Thick-headed Fly: In late afternoon on May 12 I noticed a fly sitting on a fern in my garden. It was different from any other fly I had seen. It had a large head, a white face, and large brown eyes, and it stayed in the same spot for a long time. It turned out to be a Thick-headed Fly, a true two-winged fly in the order Diptera, and one of 14 species in the genus Myopa. The larvae of these flies are internal parasites on wasps and solitary bees, including bumblebees. I have a lot of bumblebees in the garden and this fly may have been waiting for one. It had the characteristic Myopa pose with its hind end down and its head up. Its plan would be to attack a bee or wasp in flight and oviposit a single egg between the abdominal segments. The larva would hatch inside the host and feed there until it was ready to pupate. At this point the host is depleted and dies, but nothing is wasted. It continues to serve the fly. Its exoskeleton provides an added layer of protection for the pupa.

Fishfly: On May 15, my neighbor Jon Golden called me to come and see a large insect on his front door. It was a female Spring Fishfly, Chauliodes rastricornis. Chaulio is from Greek and means “impressive.” The species name rastricornis means rake-horned and describes the antennae. It is in the order Neuroptera which means “nerve wings” and refers to the prominent veins in the wings. This insect was about one and three quarter inches long not counting her antennae. Her wing span was about three inches. The silvery gray wings were partly translucent and showed off the veins. The gray patch in the left side of the photo is the batch of eggs she had just laid. These would normally have been laid on vegetation near a pond but Fishflies, like moths, are attracted to night lights. This one unfortunately laid her eggs in a place where the hatching larvae can’t crawl to water. Fishfly larvae are aquatic, omnivorous creatures known as hellgrammites. They have strong mandibles which can give a person a good nip, and a hose-like tail which they extend and retract as needed to get air.

Turn the tables: Thick-headed Fly may seem like an insensitive name but it is simply descriptive. If flies were to name us, they would see that in our eagerness to kill them we will go so far as to risk the health of anything, everything, including ourselves. They would call us fat-headed people.

Sources:; Borror and DeLong’s Introduction to the Study of Insects, Charles A. Triplehorn, Norman F. Johnson; Insects, Their Natural History and Diversity, Stephen A. Marshall;

Submissions and ideas for the Biodiversity Corner are encouraged on any species that occurs in the wild and was seen in Carlisle. Send a note, photo or the whole column to If you have a mystery species, send that too.∆

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