J. A. Rudinsky

Sound production in Scolytidae: Stridulation by female Dendroctonus beetles

Abstract A new stridulatory apparatus on the last sternite and the eighth segment is described in six female Dendroctonus bark beetles, and elytral files similar to those of males are found on four of these species, which were hitherto believed to be silent. Electronically recorded sounds include an infrequent ‘spontaneous’ click from females alone and rapidly repeated clicks (D. pseudotsugae and D. rufipennis) or a multi-impulse chirp (D. brevicomis and D. ponderosae) from females in close acoustic range of other females. An intraspecific spacing function during gallery site selection is suggested.

Sound production in Scolytidae: specificity in male Dendroctonus beetles

Abstract The male stridulatory apparatus of six Dendroctonus bark beetles is described, showing species-specificity especially in the elytral files. Typical male stridulation of D. pseudotsugae and D. ponderosae at the chemostimulus of each females attractant and at stress when handled, is found to be distinct and specific when electronically recorded.

Sound production in Scolytidae: Female sonic stimulus of male pheromone release in two Dendroctonus beetles

The hypothesis that female sonic stimulus may evoke male pheromone release in a behavioural interaction analogous to the known male sonic stimulus of female pheromone release, was confirmed in Dendroctonus pseudotsugae, and also in D. brevicomis. In both species known male-produced substances collected from males stimulated by recorded female stridulation were identified by coupled gas chromatography/mass spectrometry. In a second test with D. pseudotsugae, male pheromone release during recorded female stridulation was evident in the change of male stridulation from the simple attractant chirp to the interrupted chirp, which is known to result from a medium concentration of 3,2-MCH. Also, the D. pseudotsugae male attractant chirp was synthesised with an electronic pulse generator and used to evoke pheromone release. It is concluded that the antiaggregative pheromone of this species is released by each sex at the sonic stimulus of the other sex.

Sound production in scolytidae: ‘Rivalry’ behaviour of male Dendroctonus beetles

Abstract Intrasex response of two males at the gallery of an attractive female included ‘rivalry’ stridulation that was distinct in certain acoustic properties from chirps evoked by the female attractant. With the southern pine beetle, Dendroctonus frontalis , comparison of chirps evoked by natural and synthetic chemostimulus confirmed that myrtenol is part of the female attractant, that verbenone is multifunctional according to its concentration, and that endo -brevicomin has a rivalry function as well as its anti-aggregative effect. Considerable acoustic specificity was apparent in tested chirps of three bark beetles.

Pheromones released during inter- and intra-sex response of the Scolytid beetle Dendroctonus brevicomis.

Pheromones of Dendroctonus brevicomis released variously during inter- and intra-sex response (including stridulation by both sexes) were the known pheromones exo-brevicomin, endo-brevicomin, frontalin and verbenone, and substances identified as pinocarvone, trans-pinocarveol, and myrtenol. These substances are present in emergent beetles and thus attack of a host tree is not essential for their initial production.

Isomer of antiaggregative pheromone identified from male Douglas-fir beetle: 3-Methylcyclohex-3-en-1-one

A compound previously detected in volatile material released by Dendroctonus pseudotsugae was identified by coupled gas chromatography/mass spectrometry as 3-methylcyclohex-3-en-1-one (3,3-MCH). This is an isomer of 3-methylcyclohex-2-en-1-one (3,2-MCH, formerly called MCH), a multifunctional pheromone of this species. Not previously reported in natural products, it was collected from live male beetles in larger quantities than 3,2-MCH and frontalin, which were also released.