Longevity and Weight Loss of Free-flying Male Cecropia Moths, Hyalophora Cecropia (Lepidoptera: Saturniidae)

During their spring flight season, free-ranging male cecropia moths lived a maximum of 12 days (one of 124 recaptured moths of 387 released moths). The number of survivors declined precipitiously after day five; five to seven days is probably the usual life span. The recaptured moths did not have different initial weights than those that were not recaptured. The larger the moth the more absolute weight it lost and the faster it lost weight during the first few days. A moth lost about 20% of its weight during the first night of flight and accumulated about a 40% weight loss during the remainder of its life. Adult saturniid moths do not feed and live only a few days in captivity (Rau and Rau 1912. 19 ~: Janzen, 1984). The details of their brief adult lives have not been studied with free-living adults. Here we ask how long free-flying adult male cecropia moths live in nature and how much weight they lose as they age. This information is important to understanding how resource harvest as a larva is integrated with the duration of the non-feeding post-larval stages, and how weight loss influences flight dynamics (Janzen 198~1. Cecropia. Hmlophora cecropia (L.) (Lepidoptera: Saturniidae), ranges over the United States and southern Canada east of the Rocky Mountains (Ferguson 1972, Lemaire 1978). Its natural history and ecology have been most intensively studied in Illinois (e.g., Marsh 19~1. Waldbauer and Sternburg 1973, Sternburg et al. 1981). As part of the Illinois studies. the rv.o senior authors released, weighed, and individually marked newly emerged adult males in the contiguous cities of Champaign and Urbana during the natural 1968 cecropia tlight season (rnid-~lay to early July). Many were reweighed after being recaptured in traps baited with virgin females. Adult ca.LOpias usually emerge from the cocoon about 5 h after sunrise (ca. 1000 h). Emergence is delayed on cool days. They crawl a few centimeters to a place where the wings can expand and then remain there until sunset. Shortly after sunset both newly emerged and old males make a dispersal tlight that, judging by the activities of caged males. may continue for as l ng as an hour. The newly emerged virgin females are inactive until an hour before da\\n: then they evert the gland that produces the sex attractant pheromon<:. The males. again active at this time. seek out the females by flying to the pheromone source. These activities cease at d wn. Pairs stay coupled about 16 h, until the following sunset. The males then disperse and the females fly for the first time, seeking oviposition sites. ~lated f males make oviposition flights every night but are not known to mate or release sex pheromon<: again. ~lated males continue to disperse just after sunset and to fly in search of unmated females just before dawn each day (Waldbauer and Stemburg 19791. :Depanrnem of Emornology. l"ruYersity of Illinois. Crbana. IL 61801. -Depanrnem of Biology. l"ni\ersity of Pennsyhania. Philadelphia, PA 19104. 1 Waldbauer et al.: Longevity and Weight Loss of Free-flying Male Cecropia Moths, Published by ValpoScholar, 1985 134 THE GREAT LAKES ENTOMOLOGIST VoL 18, No.4 MATERIALS AND METHODS The moths emerged from overwintered cocoons that had been collected in Champaign­ Urbana or reared outdoors from local stock as described by Waldbauer and Sternburg (1973). All cocoons were held until emergence at ambient outdoor conditions. The moths emerged synchronously with the wild population, putting our traps in competition with a large population of wild females (Sternburg and Waldbauer 1969, Fig. 4). Males were released on the day they They were first numbered in sequence with a waterproof felt pen on the underside left hind wing and then weighed o the nearest 10 mg between 1300 and 1500 h, long after they had excreted the meconium. Some dribbled a bit of meconium afterward. These were reweighed except for a few that dribbled slightly at the time of release. The males were released between 16 May and 30 June in a park near the center of Champaign-Urbana. Those released in daylight (40%) were put in trees or shrubs where they were hidden by foliage. Those released around dusk (60%) were tossed into the air and llew off. The number of moths recaptured and the number reweighed differs because five recaptured moths that had been damaged by birds were not reweighed. The traps (Sternburg and Waldbauer 1969) were constantly baited with at least two virgin females that were replaced at least every three days. A trap at the home of GPW was 2.9 km west of the release point Another, at the home of JGS, was 3.9 km east of the release point. The area between the traps consists mostly of urban residential areas with many trees and shrubs. At the lime of the study i had a large wild cecropia population (Sternburg et aL 1981). The traps were examined daily. Recaptured males were reweighed at the laboratory between 1300 and 1500 hand re-released at the trap in which they had been caught. in late afternoon at the GPW trap and just after dark at the lGS trap. If released in daylight at the lGS trap, they were attacked by blue jays (Cyanocitta cristata) and common grackles (Quiscalus quiscula). Release time had no significant effect on the probability of recapture; at the GPW and l S traps, 38.5% and 36.0% respectively, of the re-released moths were recaptured at least once more (x 0.016, P = 0.9, 1 d.t., continuity corrected) .