Busy lives of small homebodies

April 17th, 2007

Busy live of small homebodies

The CUIC recently received a loan return from Dr. Gary Gibson, of the Canadian National Insect Collection in Ottawa. The specimens he identified for us were of the parasitoid wasp family Pteromalidae; Alloterra trilineatus (Yoshimoto). All of our specimens were females and have a body about 1.5 mm long.

Alloterra trilineatus (Yoshimoto)

Questions you might ask?

Q1. If she is a wasp where are her wings?

A. The females of this species are brachypterous, and have only been found in leaf litter in forests. You can see the small spike-like forewing rudiment under her tegula and above the leg on the mesothorax. The males have wings and are collected in flight traps.

Q2. How did the CUIC get these specimens?

A. In the late 1990’s, Cornell University obtained an 8-hectare plot of virgin forest near Newfield in a land swap with Weyerhaeuser Corp. This land was dedicated as the Richard Fischer Old-Growth Preserve. Curtis Ewing and I sampled this site over 3 different years, using Berlese extractions of leaf litter samples. These wasps were stored in alcohol along with numerous other small adults, as we focused on beetle, bugs and ants for another study. Kojun Kanda arrived in the CUIC and wanted to learn more about parasitoids, so he prepared these specimens, among others, and when two Canadian dipterists visited last month, they took the specimens to Dr. Gibson, an expert on Chalcidoidea. He kindly determined the specimens, keeping two for the CNC.

Q3. Why is this minute insect important?

A. We can ask that question of ourselves as well, but in fact, this sample of 9 female A. trilineatus is important because it comes from a site highly disjunct from the known range of this species. The species as was described based on 11 female specimens and about as many males collected in Missouri, Oklahoma, Tennessee, North Carolina and Washington, D.C. The occurrence of this species at Fischer Preserve is consistent with the previously collections of numerous other southern insect species in this woodlot. These species are most often known from the Potomac River valley and further sourth in the  Appalachians. In the CUIC, specimens of such species are most often represented by material collected by the Smithsonian entomologist, H.S. Barber, who worked extensively at Plummer’s Island, VA. We had no specimens of A. trilineatus in the CUIC before these.

Q4. Who was Yoshimoto, and why is his name in parentheses?

A. Carl Yoshimoto was a Ph.D. student of Howard Evans here at Cornell, receiving his Ph.D. in 1956, two years before John Moser received his degree with Professor Evans. By the way, Howard married Mary Alice Dietrich, daughter of Henry Dietrich, one of our former curators. Carl went on to work at Bishop Museum in Honolulu, and later the Canadian Forestry Service. His name is in parentheses because he proposed the name trilineatus to be placed in the genus Trimicrops, a genus based on a European species. Paul Dessart of Belgium moved our species to the new genus Alloterra, which he proposed in 1996.

Q5. If Alloterra trilineatus is a parasitoid, what does it parasitoidize?

A. The descriptions of this and related species in the subfamily Diparinae do not list any host associations, so basically nobody has any idea. Recent work has begun to associate the winged males with the wingless females in species of this subfamily, as originally the two sexes were often described in different genera. One might sequence mtDNA from a field-collected female and then search among DNA extractions of various soil-dwelling fly and beetle larvae living at Fischer Preserve in hopes of getting a match with a parasitized host, a technique much like Prof. Kelly Tilman, South Dakota State University, used in her Cornell Ph.D. work with Prof. Mike Hoffmann.

If you go to Fischer woodlot, remember that it is an official Cornell Natural Area administered by Cornell Plantations, and you need to obtain permission to collect insects. At any rate, you should respect the forest and the many downed logs, as insects have lived there since glacial Lake Spencer drained at the end of the Wisconsin Glacial Period. And when you go, make sure you look back at campus not 7 miles away across the valley. You needn’t go far to pass the boundaries of knowledge.

James Liebherr-Curator