FUNCTIONAL DESCRIPTION OF WITHIN-TREE LARVAL AND PROGENY ADULT POPULATIONS OF DENDROCTONUS FRONTALIS (COLEOPTERA: SCOLYTIDAE)

Abstract

Can. Ent. 108: 363-372 (1976) Within-tree larval and progeny adult populations of Dendroctonus frontalis Zimm. attacking loblolly pine, Pinus taeda L., were investigated in order to define the distribution of larvae within sample units (100 cmZ disks of bark) and to describe the functional relationship of both larvae and progeny adults to the infested portion of the tree bole.Larvae and progeny adults were sampled over the infested bole of the 50 trees. Two separate measures of progeny adults were obtained. The first measure was taken just prior to emergence from the tree and the second measure was obtained by rearing the insect until emergence from the sample disks was completed.Larvae were found to be uniformly distributed within the total disk. The functional relationship of the larvae and the two measures of progeny adults to the normalized height on the infested bole was described by the two parameter nonlinear model y = Ax(1 -x)eBX.Highest larval density along the infested portion of the tree bole occurred just below the center and tapered abruptly towards the base and gradually towards the top of the tree. The density of progeny adults on the other hand was greatest just above the center portion of the infested bole and tapered abruptly towards the top and gradually towards the base of the tree. Both measures of progeny adults produced curves of virtually the same shape. However, the density of progeny adults was substantially less in the samples which were reared indicating that mortality agents continued to act on the population until emergence from the tree.

Evaluation of traps used to monitor southern pine beetle aerial populations and sex ratios

“…where y is the density of beetles at relative height x , and a and b measure the amplitude and shape of the curve, respectively (Mayyasi et al . 1976).…”

“…1976). From a large number of pines, Mayyasi et al . (1976) estimated a and b to be 37.44 and 0.42, respectively, and obtained a very good fit to the curve.…”

“…First, the actual density ( Y a ) of marked beetles (per 100 cm 2 ) at the trap midpoint was estimated from the total number of beetles captured in the emergence traps. We then calculated the expected density ( Y e ) at the same location using Mayyasi et al . (1976) estimates of a and b .…”

“…The height of the sticky traps varied between the treated and untreated infestations in order to adjust for the difference in height of the developing brood. For untreated infestations, trap height (height of upper edge) was set at 5 m, which corresponded approximately to the trunk height of maximal beetle density (Mayyasi et al . 1976).…”

Effect of Intraspecific Competition on Progeny Production ofTomicus piniperda(Coleoptera: Scolytidae)

“…Several studies on intraspeciÞc competition in several bark beetle species report that higher attack densities result in lower female fecundity and lower weight of progeny adults (McMullen and Atkins 1961, Beaver 1974, Berryman 1974, Mayyasi et al 1976, Light et al 1983, Anderbrant et al 1985, Sauvard 1989, Anderbrant 1990, Zhang et al 1992, Hui and Longshu 1995. Although the effect of intraspeciÞc competition on weight of progeny adults (males and females) has already been examined (Beaver 1974), so far there are no reports indicating whether both sexes are equally affected.…”