SEASONALITY, LONGEVITY, HOST CHOICE, AND INFECTION EFFICIENCY OF SALTICELLA-FASCIATA (DIPTERA, SCIOMYZIDAE), A CANDIDATE FOR THE BIOLOGICAL-CONTROL OF PEST HELICID SNAILS
Jb. Coupland et al., SEASONALITY, LONGEVITY, HOST CHOICE, AND INFECTION EFFICIENCY OF SALTICELLA-FASCIATA (DIPTERA, SCIOMYZIDAE), A CANDIDATE FOR THE BIOLOGICAL-CONTROL OF PEST HELICID SNAILS, Biological control, 4(1), 1994, pp. 32-37
Host specificity and seasonal incidence of parasitism by the sciomyzid
fly Salticella fasciata was studied at a site near Montpellier, Franc
e, and in the laboratory. In field collections, only adult snails (> 1
1-mm diameter) of the pest helicid species Theba pisana and Cernuella
virgata were found bearing eggs of S. fasciata in their umbilicus. Fli
es were present in the field from September to June, which coincides w
ith the active breeding period of the host snails. The percentage of a
dult snails bearing fly eggs increased with time while the adult snail
population decreased through mortality after breeding. In choice expe
riments, both T. pisana and C. virgata were significantly preferred as
hosts when maintained in pairwise combinations with the co-occuring p
est helicid species Cochlicella barbara, Cochlicella acuta, and Helix
aspersa. Surprisingly, fly larvae were found to be inefficient at infe
cting and killing host snails though they fed readily on the decaying
tissues of manually killed snails. The host-specific oviposition habit
of the fly and larval killing inefficiency are discussed in relation
to both the behavioral evolution of the Sciomyzidae and the inappropri
ateness of this species as a biological control agent of terrestrial s
nails. (C) 1994 Academic Press, Inc.