Our objective was to measure mating success of gypsy moth females in sparse populations beyond the leading edge and compare it to male catch rate in pheromone-baited traps.
Females were dissected and their spermatheca was analyzed for the presence of sperm. The spermatheca in fertilized females was filled with sperm. The spermatheca of unfertilized females was transparent and empty.
The proportion of mated females per day (P) was estimated as:
P = 1.0 - exp(-sM)
here M is male catch rate per day, and s is a parameter estimated using non-linear regression. Parameter s=0.15 is interpreted as the instantaneous probability of female mating per day when male capture rate is 1 male/trap/day. To convert male capture rate per day to capture rate per season, multiply it by 15.
Average mortality of females due to predation was 52%. Probably, ants were the major predators.