Rearing stable fly larvae (Diptera : Muscidae) on an egg yolk medium

The growth and survival of Stomoxys calcitrans (L.) larvae on egg yolk medi um inoculated with bacteria isolated from a colony of stable flies was eval uated. Five species of bacteria-Acinetobacter sp., Aeromonas sp., Empedobac ter breve (Holmes & Owen), Flavobacterium odoratum Stutter, and Serratia ma rcescens Bizio-were identified according to fatty acid profiles using a mic robial identification system. Larvae failed to develop on uninoculated plat es, confirming that bacteria are required to complete development. Larvae a lso failed to complete development on plates inoculated with Aeromonas sp. and S. marcescens, and died during the Ist instar. Larvae completed develop ment on the remaining 3 bacterial species as well as on Escherichia coli (M igula). Survival was generally higher when larvae were reared on Acinetobac ter sp. and F. odoratum compared with E. coli and E. breve. Egg density did not influence larval survival, although the variability in survival was lo west using 20 and 40 eggs per plate. Larval survival in mixed cultures of A cinetobacter and Flavobacterium averaged 22.7% lower than survival in the p ure cultures, and averaged 21.6% higher in mixed cultures of Empedobacter a nd Flavobacterium compared with pure cultures. Larval survival in mixed cul tures did not differ significantly from mean survival in pure cultures for combinations of Acinetobacter and E. coli, Acinetobacter and Empedobacter; E. coil and. Empedobacter, and E. coil and Flavobacterium. Larval developme ntal time was faster on all mixed bacterial cultures compared with developm ental time on pure bacterial cultures. Optimal sample sizes and egg numbers are presented for detecting specified differences in larval survival. This rearing procedure will be useful for studying insect-microbe interactions and evaluating mortality using bacterial agents.