Diapausing Stages Research Articles

Hydrocarbons in the surface lipids of pupal tobacco budworms, Heliothis virescens

The surface lipids from pupae of the tobacco budworm, Heliothis virescens, had five homologous series of alkanes. Normal alkanes from 17 to 34 carbon atoms comprised 33% of the alkanes; heptacosane was the major constituent at 11%. Monomethylalkanes comprised 50% of the alkanes and consisted of terminally branched 2- and 3-methylalkanes and internally-branched components. The 9-, 11-, 13-, and 15-methylhentriacontane isomers were the major constituents at 24%. Dimethylalkanes from 33 to 35 carbon atoms comprised 14% of the alkanes. One GLC peak was tentatively identified as a mixture of 11,19- and 13,21-dimethyltritriacontane. Analyses of the hydrocarbons of four strains of pupae showed no difference in the type of hydrocarbons found in the cuticular surface lipids. However, a non-tanning body mutant of one strain did show an increase in the amount of hydrocarbon present. There was no difference in the amount of cuticular surface lipid on diapausing pupae compared with that on non-diapausing pupae. Furthermore, there was no difference in the amount of cuticular surface lipid on male pupae when compared with female pupae in both diapausing and non-diapausing stages of development.

Tolerance of the diapausing stages of four species of Lepidoptera to methyl bromide

The diapausing stages exposed to methyl bromide were larvae of Ephestia elutella (Hübner) and Plodia interpunctella (Hübner), pupae of Pieris brassicae (L.) and eggs of Bombyx mori (L.). Diapausing larvae of Ephestia elutella were highly tolerant, a few surviving to the adult stage after exposure to concentration-time (CT) products of up to 150 mg hr/l at 25°C and 260 mg hr/l at 15°C. Diapausing larvae of Plodia interpunctella were tolerant at low temperatures but quite susceptible at 25°C. In both species, larvae in diapause were four to six times more tolerant than other larvae at 15°C or below, and strains recently collected from the field were more tolerant than laboratory reared stocks. In E. elutella, differences in the method of induction, maintenance or termination of diapause did not affect tolerance to fumigation. P. interpunctella larvae reared at high population density were more susceptible than those reared at low density. Among strains of these species, a correlation was observed between the duration of larval diapause and tolerance to methyl bromide. Adults emerging after fumigation of diapausing larvae were of lowered fertility but rarely sterile. The CT products required for the complete control of moths in diapause were higher than those currently recommended for the disinfestation of stored products. Diapausing pupae of an outdoor species Pieris brassicae required the very high CT product of 403 mg hr/l for complete control at 25°C and were at least six times more tolerant than non-diapausing pupae. Diapausing eggs of Bombyx mori required 179 mg hr/l for complete control, while non-diapausing eggs were all killed by 125 mg hr/l.