Gypsy Moth Mating Success

Gypsy moth is an introduced forest pest insect in North America. Gypsy moth females attract males using pheromone communication.

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.

Methods

Nine plots were selected in the area recently infested by gypsy moth in Virginia and West Virginia. In each plot, 4 pheromone traps and 18-30 tethered gypsy moth females were exposed for the same time. Dead males taken from the trap look nice. Tethering did not interfere with mating.

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.

Results

The proportion of fertilized females increased when male catch in pheromone traps increased (Fig.1).

Fig. 1. Relationship between male catch in pheromone traps and mating probability.

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.

For information contact Alexei Sharov
E-mail sharov@vt.edu