A CHARACTER DEMONSTRATING THE OCCURRENCE OF MATING IN MALE CACTOBLASTIS CACTORUM (LEPIDOPTERA: PYRALIDAE)

The arrival of the cactus moth, Cactoblastis cactorum (Berg), in the southeastern United States in 1989 (Mahr 2001), and its steady progress westward to the Opuntia -growing regions of Mexico and the southwestern United States have resulted in research on the development of control measures to halt or slow the movement of the insect. The most promising control measure against C. cactorum is the sterile insect technique (SIT), in which large numbers of male moths are exposed to a sub-sterilizing dosage of ionizing radiation and then released in or in front of the leading edge of the geographic range of the pest. Irradiated males then find wild females, mate with them, and produce progeny which are delayed in development from oviposition to eclosion, fewer in number than in a normal mating, and sterile (Carpenter et al. 2001). Irradiated male C. cactorum released in the SIT program are marked with colored dye to allow their identification as released males upon recapture in pheromone traps (Hight et al. 2005). In order to compare mating success of wild and irradiated males, an anatomic characteristic that indicated the mating status of males was sought. A number of published reports mention that differences in color of secretions in the ductus ejaculatorius simplex in various Lepidoptera species allow determination of mating status of males. Proshold (1991) found that the simplex in unmated males of a noctuid, Heliothis virescens, the tobacco budworm, varied from light yellow to dark brown. The simplex in mated males was clear, cloudy, or white. In Spodoptera frugiperda , the fall armyworm, also a noctuid, Snow & Carlysle (1967) reported that the color of the primary simplex (Callahan 1958) was light brown to black in unmated males and transparent to yellow in mated males. Furthermore, they reported that a dark spermatophore is transferred to the female at the first mating and that subsequent spermatophores are lighter in color. These authors also reported that mated males held for several days and prevented from mating regenerated only a yellow or light brown color in the simplex , and that this color was never as intense as the brown to black color indicative of unmated males. Similar results were reported by Haines (1981) for the noctuid, Spodoptera littoralis, by Henneberry & Clayton (1984) for the noctuid H. virescens , and by Bergh & Seabrook (1986) for the tortricid , Choristoneura fumiferana . These latter authors also summarized results from the above 4 species. Except in H. virescens , the color of the simplex was regenerated within several days after mating. Callahan & Cascio (1963) described the male reproductive system of the noctuid, Heliothis zea , and reported that the simplex consisted of a posterior or cuticular portion, and an anterior or primary portion. They identified two secretory areas of the primary simplex and found that the posterior, or first secretory area, of the primary simplex was variously colored in different noctuid species and, because of the easily traceable color, was the first secretion to enter the female bursa during mating. Outram (1971) stated that the bulla seminalis of the female contained a fluid similar in color to the secretion of the primary simplex in C. fumiferana , the spruce budworm, but that the function of the fluid is not known. Outram (1970) also described and illustrated the male reproductive system of C. fumiferana and reported that 7 regions, distinguishable on the basis of differences in secretions and constrictions in the duct, could be identified in the primary simplex of this species. However, Callahan & Chapin (1960) found little morphological variation in the primary simplex in several different noctuid species, but were able to use characteristics of the cuticular simplex to separate individual moths by generic groups.