Field Introductions and Establishment of the Tadpole Shrimp, Triops longicaudatus (Notostraca: Triopsidae), a Biological Control Agent of Mosquitos

The tadpole shrimp (Triops longicaudatus LeConte) is a potential biological control agent for some species of mosquitoes developing in temporary aquatic habitats. It is an effective larval predator that also actively deters mosquito oviposition. Its use in practical control programs depends in part on its ability to establish permanent populations where it is introduced. Introductions of its desiccation-resistant eggs (both lab-reared and field-collected) as well as gravid adults were made in 16 ponds in southern California. Tadpole shrimp density was monitored over five floodings from Fall 1991 through Summer 1992. The tadpole shrimp was able to colonize and persist in 94% of the ponds. All methods of introducing T. longicaudatus were successful, but its hardy egg is the preferred stage for field distribution. The hatching rate for lab-reared shrimp eggs in the ponds ranged from 13.7 to 19.4% ( = 15.9%, N = 1135-2353/pond). In a following experiment, a high density of tadpole shrimp was shown to have a significant negative impact on mosquito larvae (Culicidae) (P < 0.05), and on nontarget midge larvae (Chironomidae) (P < 0.05), but not on two other abundant insects-mayflies (Baetidae) or brine flies (Ephydridae).