Abstract. Although on-animal topical treatment with compounds such as imidacloprid has revolutionized the control of the cat flea, Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae), the development of insecticide resistance is a continuing threat. As part of a highly co-ordinated and unprecedented resistance monitoring programme for C. felis, 1437 flea isolates were collected by veterinary clinics in Australia, Germany, France, the U.K. and 29 states in the U.S.A. from 2002 to 2009. About 65% of the collections were made from June to October each year and 71% of the collections were from cats. Collections of flea eggs were sent to one of five different laboratories, where they were tested with a diagnostic dose of imidacloprid (3 p.p.m.) applied to larval flea-rearing medium. Of the 1437 collections received, 1064 contained adequate numbers of eggs for testing. Of these isolates, untreated eggs failed to hatch in 22.7% and were not considered valid bioassays. Survival rates >5% and development of adult fleas (a threshold for further testing) occurred in only 22 isolates. They were re-tested with the same diagnostic dose and none produced >5% adult emergence. Complete dose-response bioassays were performed on three of the isolates that had triggered a second test and produced slopes, intercepts and LC 50 values similar to those for existing susceptible laboratory strains. Results confirmed sustained susceptibility of C. felis to imidacloprid, despite its widespread use for over a decade.

Abstract:The Giant River Prawn is an important commercial species from southeastern Asia and has a large global market. It has a complex life cycle in which it undergoes several molting sequences. Many arthropods require firm perches on which they can perform ecdysis. We investigated preference for substrate slope and its influence on ecdysis. We discovered that prawns occupy horizontal surfaces more frequently than others, but during pre-molt and molt stages, they shift their habitat use to non-horizontally sloped surfaces. Here, they will flex their shell and later molt. We recommend modification of cannibalism management in commercial facilities by providing sufficient vertical (strongly preferred) or high-sloped (greater than 30 degrees) surfaces to facilitate ecdysis, while providing much horizontal space for foraging and other activities. This should create habitat separation between foraging and highly susceptible freshly-molted prawns, thus leading to reduced cannibalism-related mortality.