Abstract:
The objective of this investigation was to clarify the
adaptive significance of female sexual behaviours in the house
cricket, Acheta domesticus, and the Texas field cricket, Gryllus
integer. Experiments were focussed primarily on: nutritional
factors affecting female reproductive success; the ontogeny of
female sexual behaviours; female mating frequency and progeny
production; and the pattern of sperm competition.
Reproduction of singly mated female A. domesticus assigned
to 3 nutritional regimes was compared . Females fed a vitamin
and protein-enriched mouse chow, cannibalistic females, and
starved females produced on the average, 513 , 200 and 68 offspring,
respectively. Cannibals probably could not obtain the same amounts
of essential nutrients as females fed mouse chow. Reabsorption
of oocytes was likely the major factor contributing to the
decreased reproduction of starved females. In addition, female
!. domesticus fed mouse chow, but allowed constant access to
males produced 11 times as many offspring than did females fed
corn meal. Females fed corn meal probably could not absorb or
synthesize enough dietary lipids, thus resulting in poor ovariole
growth.
Female !. domesticus first mate at an average adult age
of 7 days, closely corresponding to when they first exhibit
positive phonotaxis. Females mate repeatedly and often consume the externally attached spermatophore. In ~. domesticus, females
allowed constant access to males produced significantly more
offspring than did single maters. Similarly, doubly mated G.
integer females produced more offspring than did single maters.
This difference resulted largely from the failure of many single
maters to reproduce. Remating by female crickets partly functions
in offsetting the possibility of a failed initial mating. Nymph
production increased significantly with the time the spermatophore
was attached in singly mated ~. domesticus. Spermatophore
consumption by the female was not affected by male guarding
behaviour, and the interval between mating and eating of the
spermatophore may often be shorter than the time required for
maximum insemination. Some degree of sperm depletion in singly
mated !. domesticus and G. integer may have occurred. The
patterns of daily offspring production of singly and multiplymated
females suggests that a factor provided by a male during
mating stimulates female oviposition and/or egg production. Female
crickets also might acquire nutrition from spermatophore consumption,
a benefit that is augmented by female multiple mating. The
electrophoretic examination of various allozymes in ~. integer
did not permit determination of a pattern of sperm competition.
However, the possibility of last male sperm predominance is
related to male guarding behaviour.
