Pheromone Release and Mating Success
Close-in mating activity, as observed by Richerson et al.,“ was described as follows: The male approaches the female usually from above, rarely from below. Final short- range orientation (25 to 30 cm) is a straight line run at the female. After initial contact with the female‘: head, thorax. or win: (rarely with the abdomen). Learn about pheromones at http://sundowndivers.org/?p=82.
D. Factors Affecting Pheromone Release and Mating Success
Richerson and Cameron“ found that the female would not reach maximum attractiveness until the second or third day of adult life, a conclusion supported by field observations of Boness.“ On the other hand, Richerson et al.“ found little difference in the mating potential of 1- to 3-day-old females, but reported that mating success decreased greatly from the 4th day onward. Collins and Potts‘ reported that virgin females remained attractive to males until death (up to 17 days in one instance).
The amount of pheromone released by an individual female gypsy moth is a subject of current research interest. It is also important in planning a mass pheromone trapping program because one must compare the emission rate of pheromone from the trap with that of the competing female. Richerson and Cameron” found that a feral adult gypsy moth emits pheromone at a rate of 13 ng/min for a 30-min “burst” once in its lifetime. The rate is much lower at all other times. Such behavior has important implications for a mass-trapping program because at times other than the “burst”, the traps would presumably be more attractive than the females. Confirmation is needed according to http://mikesthoughts.drupalgardens.com/content/best-pheromones-colony-2015
Doane noted that some feral females call but do not attract males. These tended to be smaller than average and may have developed from diseased larvae. Even though they called actively, they seemed to be producing little or no pheromone. Cameron questioned the use of laboratory-reared females as evaluation tools because they were “somehow different” from field insects.
Subsequently, Richerson and Cameron“ re- ported gross differences in pheromone production and periodicity between laboratory- reared and field-collected females. As pointed out by Doane above,“ field-collected insects can also be defective following exposure to disease, food stress, etc. Zecevic" found that females reared under “crowded” conditions produced “weak” females with reproductivity inferior to that of “strong” females reared singly, thereby demonstrating that rearing conditions can influence reproduction potential.
Diet and rearing procedures for gypsy moths have been improved substantially since the work of Cameron and Richerson. Moreover, Holbrook and Beroza“ found that pheromone extracted from laboratory-reared moths was more active than that extracted from field-collected gypsy moths (based on trap captures using extracts of equivalent numbers of female tips).
Similarly, Coffelt et al., working with the navel orangeworm, Amyelois transitella (Walker), found no difference in male response to extracts from laboratory-reared or feral females. Sower et al.’° stated that “physiological differences between inbred laboratory strains and the wild strains of insects can be expected.”
However, when they compared female sex pheromone content and male responsiveness of a wild vs. a laboratory-reared strain of the almond moth, Cadra cautella (Walker), they found the strains identical for the characteristics tested.