Reproduction in diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae): Morpology, behavior, and chemical ecology

Reproduction by Plutella xylostella (L.), the diamondback moth, was investigated in a series of experiments employing several techniques to ascertain details of copulation and oviposition. Internal reproductive morphology and genitalic configurations during copulation were elucidated. Reproductive structures were mostly typical of Lepidoptera with a few peculiarities. Morphometric differences were observed in comparisons of seven distantly-separated populations, and the possibility that larval diets effect these differences is discussed. Observations of ovipositing moths led to descriptions of behaviors that occur in probabilistic sequence; these behaviors are thought to facilitate identification of potential oviposition sites. Bioassays suggested contact chemical stimuli are required for egg deposition but plant volatiles decrease time required for host acceptance. Tactile information appeared to be important for egg location only. Field and laboratory choice experiments with normal (waxy) and reduced (glossy) wax blooms provided evidence that epicuticular features are extremely important in host preferences. Glossy plants accumulated more eggs regardless of plant age. However, similar numbers of eggs were deposited on parafilm-transfers of leaf surfaces and characteristics other than parafilm adherents must be involved in distinguishing glossy from waxy morphotypes. Headspace extracts of glossy and waxy B. napus, S. alba , and D. carota were collected and used in gas-chromatography coupled with electroantennography. Females and males responded to several components of B. napus and S. alba extracts, but components eliciting responses did not necessarily co-occur. Few responses were elicited by volatiles of D. carota, a non-host plant. It is likely that individual components of plant volatiles combine to form signature blends and act as an initial diagnostic character of host plants. Additionally, electrophysiology of contact chemosensory sensilla revealed at least two types of contact sensilla (those that respond to KCl and those that do not) and the existence of a polar compound on the surface of B. napus and S. alba that is detected by gustatory sensilla of the antennae. Possible plant characteristics influencing reproduction by P. xylostella are discussed.