Larval Trails of Cryptolestes ferrugineus (Coleoptera: Cucujidae) as Kairomonal Host-Finding Cues for the Parasitoid Cephalonomia waterstoni (Hymenoptera: Bethylidae)

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Abstract
Wandering late fourth instars of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), leave a substrate-borne chemical trail that serves as a kairomone for their host-specific bethylid parasitoid Cephalonomia waterstoni Gahan. Male C. waterstoni show no trail-following behavior to this kairomone. Experienced C. waterstoni females follow trails of ≥0.0001 larval equivalents per centimeter (LE/cm), whereas naive females show no trail following responses to dosages of Cryptolestes pusillus (Schonherr) or the red flour beetle Tribolium castaneum (Herbst). The trails of C. ferrugineus larvae are only moderately persistent. Natural trails aged on filter paper elicit trail-following responses by the parasitoid for less than one week. Artificial beetle extract trails on ground glass plates elicited trail following by the parasitoid for almost two weeks. The disappearance of both natural and solvent extract kairomonal trails follows an exponential decay model.