Geographical variation in responses to photoperiod and temperature by Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) during and after dormancy

During August, temperature and photoperiod only slightly affected the very intense diapause in field populations. By summer's end, diapause intensity diminishes, but photoperiod and temperature maintain diapause. Subsequently, Colorado potato beetles lose their responsiveness to photoperiod at high temperatures (c20°C), but at low temperatures (18-15°C) the beetles remain photoperiodically sensitive after emerging from the soil and initiating oviposition in the spring. Mated females that overwinter can lay fertile eggs without mating in the spring. Populations from climatically different areas in New York state have similar thermal thresholds (c12°C) for reproductive development after dormancy, but the Riverhead population has a less intense diapause and lower thermal requirements for initiating oviposition (K = 135 HDD₁₂ [heat-degree days]) than the Freeville population (K = 213 HDD₁₂). This diversity results in large differences in the timing of vernal emergence and oviposition at the 2 sites. -from Authors