| Abstract: | The predatory potential of two onmnivorous crustaceans, Gammarus duebeni and Palaemonetes varians, has been examined to investigate their effect as mosquito larval predators. Mature gammarids ate 4-8 Aedes detritus larvae/24 h and palaemonids, 22-30/1 h, often killing larvae when not hungry. The crustaceans were exposed to Bacillus thuringiensis subsp. israelensis (Bti) and to mosquito larvae killed by Bti with no adverse effects, endorsing the safety of this microbial pesticide. Crustacean faecal pellets, collected post-feeding and placed in fresh marsh water, were toxic to mosquito larvae the following day. After placing the crustaceans in fresh salt-marsh water for 6 days, the fresh faecal pellets failed to kill mosquitoes apart from pellets obtained from crustaceans originally fed on the highest concentration of Bti, where there was a 50% kill after 3 days of incubation. Mosquito larvae on salt-marshes are not easy to control with ecologically undesirable toxic chemicals. Encouraging the breeding of predators such as crustaceans, or even their release, could prove to be a useful method of mosquito control to supplement the periodic inundative use of the ecologically acceptable Bti. |
