EFFECTS OF FARNESYL METHYL ETHER ON THE REPRODUCTION OF THE WESTERN TENT CATERPILLAR, MALACOSOMA PLUVIALE: SOME PHYSIOLOGICAL, ECOLOGICAL, AND PRACTICAL IMPLICATIONS

Abstract

Female pupae of Malacosoma pluviale (Dyar) treated externally with 80 μl of farnesyl methyl ether during their second day retained most of their original lipid content on the seventh day, when the eggs were maturing. Control pupae lost nearly half their original score in the same interval. In contrast to controls, pupae treated with 40–80 μl (4th–6th days) developed fewer, lighter eggs, and their adults lived longer, were more active, and less inhibited in egg-laying. But the egg masses from treated individuals contained scattered, tumbled eggs and were oversupplied with spumaline.When eggs were incubated in April, those from individuals treated with ≥ 40 µl failed to hatch. Eggs from females that had received < 40 μl hatched, bur the resulting colonies died before their second instar in their normal habitat, whereas control colonies survived. Hatching of treated stock could be induced by premature incubation in January, but the numbers and quality of the emerging larvae were greatly reduced in comparison with controls.The results provide further evidence that behavioral types in M. pluviale are mainly nutritional products. Because of the treatment, developing eggs were deprived of nutrients during the pupal stage and developing adult tissues were oversupplied. Farnesyl methyl ether may have exerted its effect by acting like an excess of juvenile hormone during that part of the pupal stage in which the normal level of activity of the true juvenile hormone is thought to be very low.Field evidence suggests that an equivalent humoral imbalance sometimes may occur naturally, and thus affect a generation's reproductive capacity, especially near a peak in abundance. Hormonal mimics therefore might be used to manipulate pest populations, but this suggestion includes a cautionary note.