PARENT SESSION
Poster Session #37: Invertebrate Ecology.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Infrared warming and forced convective cooling of webs of the fall webworm caterpillar (Hyphantria cunea).

REHNBERG, BRADLEY¹, ¹

ABSTRACT- Fall webworm caterpillars (Hyphantria cunea) spin large silk webs in trees during late summer. Functions of the web are unclear but may include the maintenance of favorable caterpillar body temperatures. In my research, 19 webs were collected in the field and studied in the lab to answer three questions: How do temperatures of various regions of the web respond to infrared radiation? Can a radiation-warmed web hold heat during a cool wind? Does the web retard air movements during windy conditions? Webs were individually mounted under an infrared light source at the end of a wind tunnel. Thermocouple probes were placed at the front (outer) edge, inside middle, and back (inner) edge of the web. Probe temperatures were recorded under conditions of (1) infrared heating, (2) infrared heating during a cool wind, and (3) a cool wind without infrared heating. During infrared heating, outer and middle regions of webs were more effective at trapping and holding heat compared to inner regions. Air flows averaging 2.7 m/sec at the front of the web diminished to only 0.6 m/sec at the back of the web. Although webs strongly reduced movements of air, heat acquired during infrared exposure could not be held during windy conditions. It appears that forced convection can quickly rob webs of previously stored heat.

KEY WORDS: Hyphantria cunea, thermoregulation, infrared, web