TRAIL AND ALARM PHEROMONES IN ELASMUCHA-GRISEA (HETEROPTERA, ACANTHOSOMIDAE)

Females and immature Elasmucha grisea form an association in which the mother protects its offsprings at longest to the fourth instar. The cohesion of the protective association is assured by a trail substance which is released by the larvae when moving over the surface. Both larvae (with exception of the first instar) and mother can follow such trails. A definitively perceptible trail is first produced after the passage of several larvae (with instar 3 five larvae). A trail laid by twenty larvae (instar 3 and 4) can still be followed by larvae after half an hour. The defensive secretion of Elasmucha grisea larvae and adults has an additional alarm function. It releases attack reactions in the protecting female, i.e. a directed movement toward the source of odor and wing fanning. With exception of the first instar the larvae react to the alarm secretion with a well organized group flight. Young adults can also react to the alarm substance by falling. The larval defensive secretion is a complex mixture of substances. The 2-hexenal contained in the secretion causes a larval unrest but no typical flight reaction. © 1979 Masson.