Research: Ecology of the Antenna-waving Wasp

 

            Dr. Tramer and graduate student Erin Moan are investigating the ecology of a rare wasp whose known range in Ohio is confined to the oak openings, a small strip of sandy soil located west of the University of Toledo campus.

 

            The Antenna-waving Wasp (Tachysphex pechumani) is a solitary wasp that immobilizes a short-horned grasshopper with its sting, lays a single egg on it, and buries it in a burrow dug in the sand.  The female wasp dies after only a few weeks above ground, but its egg soon hatches and its larva feeds on the grasshopper and spends the winter within its victim’s corpse. When the sand warms up in May the larva pupates, and in June the adult wasp emerges to repeat the cycle.

 

            The project, which began in 2002 and is continuing during summer of 2003, has several objectives:  (1) To determine the wasp population size, (2) To assess whether wasps disperse from one nesting location to another, (3) To understand why wasps select certain sandy areas for burrow construction and avoid others, (4) To measure the reproductive success of the wasp, and  (5) To ascertain the agents of mortality in cases where an adult wasp fails to emerge from the burrow.  Our overall goal is to learn enough about the wasp’s ecology to develop land management strategies that will insure its continued survival in the oak openings region. 

 

            We have developed a technique for marking the female wasps with dots of non-toxic paint, and have been able to establish that wasps do not disperse more than a few dozen meters from the burrows in which they developed.   We have also determined that the density of grasshopper prey seems not to influence the location of nesting sites; rather, the density of the sand and diurnal temperature regimes seem to be the most important factors regulating nest timing and location.

 

            Several possible causes of reproductive failure have been identified, including infertile eggs, inherent developmental abnormalities in the larva or pupa, predation on the larvae by mammals or birds, and kleptoparasitism by satellite flies, which attempt to deposit their larvae on the paralyzed grasshopper before the wasp can close the burrow.  70 burrows provisioned in 2002 have been tagged and will be revisited after the wasps emerge in 2003 to estimate reproductive success.