Experimental intrusion of a small container by adults of the Indian-meal moth, Plodia interpunctella Hübner, through a tiny opening

Abstract

When adults of mixed sexes were confined in a small cage (17cm×17cm×14cm height) containing 6 smaller plastic test containers (3cm diameter, 5cm height) each of which had a small hole of 6mm diameter at the center of the sealing cap, most femeles (94.7-100%) entered the containers through the holes. Most femeles (89.4-93.3%) selected test containers with larval food (rice bran) if available, deposited their eggs, and died in the containers, producing many larvae in the food.
However, most femeles (84.6-92.9%) entered test containers even when no larval food was contained in all the containers in the cage. This suggests that mated femeles would search for and enter smaller spaces to hide, to find out larval food and deposit their eggs. Males in the mixed populations sometimes tended to enter test containers but sometimes not, suggesting that they would respond rather to other factors such as virgin females than to the containers or larval food.
When only virgin femeles were confined in the cage without males, more individuals (36.4-60.0%) died outside test containers, suggesting some behavior such as calling outside males. When only unmated males were confined without females, more individuals (77.8-92.2%) entered and died in test containers, also suggesting some behavior such as searching for females.
Both males and females could pass through smaller holes of 3mm diameter, although females clearly preferred holes of 6mm diameter when the two sizes of holes were available.
When adults of mixed sexes were confined in a larger cage (57cm×57cm×30cm height) nearly half of females (48%) entered test containers, and most of them (92%) selected test containers with larval food, suggesting that mated females sought the larval food. While most of the males (80%) died without entering the containers, and the rest of them entered the containers with larval food.
Unlike in the small cage, very few females (as well as very few males) entered test containers when no larval food was contained in all the containers in the large cage. This and the results in the small cage suggest that even female adults do not directly respond to and pass through the tiny openings, but they had to respond to and land on the shadowy area, or to food odor before finding tiny holes or crevices and getting into them.