A comparison of electrophysiologically determined spectral responses in six subspecies of Lymantria.

The spectral sensitivity of the compound eye in three gypsy moth species from six different geographical regions (Lymantria dispar asiatica Vnukovskij [Asian gypsy moth], Lymantria dispar japonica Motschulsky [Japanese gypsy moth], and Lymantria dispar dispar L. [North American gypsy moth]) was tested electrophysiologically in the wavelength region 300-700 nm. For all moths examined, a maximum response occurred in the 480-520-nm range (blue-green region) with a shoulder peak occurring at 460 nm. A smaller, secondary peak was observed for both sexes at the 340-380-nm range, which is in the region considered behaviorally maximal in night-flying insects. No peaks in sensitivity were observed between 520 and 700 nm (red region) for any of the moths tested. Based on our retinal recording data, a short wavelength blocking filter with a transition wavelength near 500 nm should reduce gypsy moth attraction to artificial lighting sources. This would help reduce the number of Lymantria-infested ships traveling to and from foreign ports.

Effect of Spring and Winter Temperatures on Winter Moth (Geometridae: Lepidoptera) Larval Eclosion in the Northeastern United States.

Field and laboratory experiments were conducted to elucidate various factors influencing the temperature-dependent larval eclosion of winter moth, Operophtera brumata L, in New England. We found no difference in duration of the embryonic stage of eggs reared from larvae collected in Massachusetts (MA) and on Vancouver Island, British Columbia (BC), where winter temperatures are rarely below freezing. The number of growing degree days (GDD) required for larval eclosion declined with the number of days chilled in the laboratory and number of days below freezing in the field, confirming the findings of previous studies. Thus, eggs hatched with fewer GDD, when the spring came later than usual. Date of oviposition had no effect on date of hatch. Eggs laid by naturally occurring (feral) females hatched sooner, with lower GDD, than eggs from laboratory-reared females from MA and BC held on the same trees over the winter. South-facing eggs on the stems of trees hatched on average 1.6 days sooner than north-facing eggs. GDD calculated from bihourly measures of temperature were 15% greater than GDD estimates based on the average of daily maximum and minimum temperatures, as used by many GDD estimates made for online sources. Over two years, the mean GDD in °C for hatch of feral eggs was 176.53 ± 6.35 SE based on bihourly temperature measurements, a 1 January start date, and a 3.9°C developmental threshold. This value varied markedly, however, between the two years.