Frass analysis to determine the diet of the predator Coccinella septempunctata L. (Coleoptera: Coccinellidae)
L. Nicole Davidson, firstname.lastname@example.org and Edward Evans, email@example.com. Utah State University, Department of Biology, 5305 Old Main Hill, Logan, UT
A variety of methods have been used to decipher what insect predators are eating in the field. One little-used technique is frass analysis. This technique may hold promise for predators that ingest pieces of their prey rather than just a liquid meal. The lady beetle Coccinella septempunctata provides a good study organism for using this technique as it is a biting/ chewing predator that is primarily aphidophagous, but will utilize other prey when aphids are scarce. The aim of this study was to test the utility of frass analysis for determining the diet of this predator. In particular, we sought to determine the extent to which C. septempunctata consumes alfalfa weevil larvae as well as aphids in alfalfa fields. Laboratory experiments revealed that within 48 hours after consumption of prey, all cuticular fragments had been voided. Feeding experiments also demonstrated that diagnostic cuticular fragments could be readily distinguished for specific prey (aphids, weevil larvae, or conspecific larvae). A field experiment was conducted next to compare consumption rates of aphids and weevils for C. septempunctata. Aphid numbers were artificially increased in experimental plots. Adults of C. septempunctata were collected from these plots, and from plots sprayed with sugar solution, and their frass was analyzed. Differences in prey use between the two sets of plots will be discussed.
Species 1: Coleoptera Coccinellidae Coccinellaseptempunctata (seven-spot lady beetle) Species 2: Coleoptera Curculionidae Hyperapostica (alfalfa weevil) Species 3: Homoptera Aphididae Acyrthosiphonpisum (pea aphid) Keywords: predation