| Popis: |
Migration occurs in some insect species, and in many cases it commences when the ovaries are immature. Environmental conditions can affect the rate of ovarian development and oviposition of insects. In the Diamondback Moth (DBM), Plutella xylostella (Lepidoptera: Yponomeutidae), the larval density affected the rate of ovarian development. In this work we determined the impact of temperatures and photoperiods on DBM ovarian development and oviposition. Fourth instar larvae were reared individually in Petri dishes at temperatures of 14 and 25oC and photoperiods of 8L:16D and 14L:10D. Emerged females were killed in a freezer and dissected under a microscope. To determine the impact of temperature on DBM oviposition, fourth instar larvae were reared individually in Petri dishes at temperatures of 14 and 25oC and photoperiods of 8L:16D. When the adults emerged, one male and one female were put in a Petri dish and the number of days for oviposition and the number of eggs laid in the first day was recorded. The results showed that the rate of ovarian development was not affected by the employed temperature or photoperiod suggesting that these factors did not affect the migratory potential of the species. Females reared at 25oC and 14oC began to lay their eggs 2 and 5 days after emergence, respectively. There were no significant differences in the number of eggs laid in the first day. The results suggested that ovipositon is delayed at low temperatures. The impact of these results on migration and dispersion of DBM are discussed. |
