Rj. Prokopy et al., EFFECTS OF EGG LOAD ON FINDING AND ACCEPTANCE OF HOST FRUIT IN CERATITIS-CAPITATA FLIES, Physiological entomology, 19(2), 1994, pp. 124-132
In studies conducted on potted host trees in field cages and in the la
boratory, we examined the influence of egg load on the finding and acc
eptance of high-ranking (kumquat) and lower-ranking (grapefruit) hosts
for oviposition by wild-origin Mediterranean fruit fly females, Cerat
itis capitata (Wiedemann). By prescribing the periods during which fem
ales had access to protein prior to testing, we generated four classes
of females having progressively increasing egg loads but not differin
g in population origin, age, degree of protein hunger at testing, or a
mount of prior experience with host fruit (none). Egg load had no disc
ernible effect on behaviour associated with finding either type of fru
it but did have a significant effect on several behaviours associated
with oviposition after alighting on fruit. Increasing egg load led to
increasing propensity to engage in ovipositional-type behaviour on bot
h kumquats and grapefruits. There was no evidence, however, to support
a hypothesis that medflies would become less discriminating against g
rapefruits relative to kumquats as egg load increased. Relative to kum
quats, grapefruits were accepted for oviposition by intermediate and h
igh egg load females to a substantially greater degree in laboratory c
ages than on trees, suggesting that results of laboratory cage experim
ents on host discrimination by tephritid flies may poorly reflect diff
erences in behavioural responses expressed under less constrained cond
itions.