EFFECTS OF A HOST-PLANT, BRASSICA-JUNCEA, ON CALLING BEHAVIOR AND EGGMATURATION IN THE DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA

The influence of the presence of seedlings of a host plant, Oriental m ustard, Brassica juncea (L.) Cos s., on the calling behaviour and egg maturation in the diamondback moth, Plutella xylostella (L.), was inve stigated. In the presence of plants, females began calling at a younge r age, began calling earlier in the night, and spent more time calling . Females which were kept with plants until after their first night of calling and then were isolated from plants, subsequently called less, at a level not significantly different from females which had never b een exposed to plants. Of all females, both with and without plants, w hich were dissected at the end of the first night of calling (n = 150) , 93 % contained mature eggs. Heavier females were significantly more likely to have mature eggs at adult emergence, to begin calling at a y ounger age and to spend more time calling on their first night of call ing. The number of developed eggs in calling females was not significa ntly different in the presence or absence of host plants on the first night of calling. However, by the second night, females in the presenc e of plants contained significantly more eggs, indicating that the pre sence of plants accelerated egg maturation, both before and after the onset of calling.