Department of Chemistry, University Ben Gurion of the Negev, Beer Sheva 84105, Israel.
The scarab beetle Maladera matrida Argaman (Coleoptera, Scarabaeidae) was first detected in Israel in 1983. Therefore, very little information on the life cycle and on chemical communication of this pest was available. The first step was to learn how to rear the beetle in the laboratory. Later, in the field trapping experiments, we found that combinations of virgin female beetles together with food were preferentially attractive to male beetles. Our field studies showed clearly that the ratio of attracted males to females to the bait of females with food was 3:2-5:4. This ratio hints that chemical communication involves an aggregation pheromone, but the constant small preference for attracted males raises the question whether the active compound is a sex pheromone released by the female to attract the male. Field observations demonstrated that the beetle is attracted to light colors and bright objects. Since the traps used in our field studies are made of yellow plastic, we had to consider the possibility that the yellow color might affect the trapping of the flying beetles and thus distort the real behavior and mode of attraction toward the source of the chemical communication. To clarify this ambiguous point, we conducted field experiments in which we compared the regular (yellow) traps with black traps and found that the bright yellow-color did indeed distort the chemical communication in the M. matrida beetle. Total catch in the yellow traps was double of that of the black traps, and the male:female ratio in the black traps was 4:1.