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The impact of foraging by Monock;tmus titillator (FAB.) on within-tree populations of Dendroctonusfrontalis ZIMM. was described. Total population estimates for D.frontalis and inner bark area foraged by M. titillator were computed for 89 loblolly pine, Pinus taeda L., sampled over a 3 year period. Frequency histograms were prepared for the surface area of habitat infested, area foraged by M. titillator, and within-tree populations of D. frontalis. These data were used to calculate the proportion of area foraged by M. titillator, the proportional D. frontalis mortality for the entire tree, and the proportional mortality occurring in the foraged area.Histograms showing the variation of these components were prepared and described using nonlinear mathematical models. Ca. 20 ~ of the infested surface area was foraged by M. titillator. Mortality to D. frontalis on a per tree basis was ca. 14 ~. Mortality in the area foraged by M. titillator was ca. 70 ~. These estimates were highly variable between individual trees and a procedure for predicting the probability of a given level of foraging and mortality was described. Sources of variation influencing foraging by M. titillator and mortality to D. frontalis were investigated. Variation between years and season followed similar trends with both foraging and mortality increasing from the base to the top of the infested bole. Variation between tree size-class was highly significant. Larger size-class trees had substantially greater foraging and mortality than did the smaller size-classes. Mortality within the foraged area was also found to be greater at the extremes of the infested bole.The southern pine sawyer, Monochamus titillator (FAB.) (Col. : Cerambycidae) is a member of the complex arthropod community that results from colonization of pine trees, Pinus spp., by the southern pine beetle, Dendroctonus frontalis ZIMM. (Col. : Scolytidae). In association with D. frontalis, M. titillator has been identified to be an interspecific competitor for food resources and habitat (COULSOY et al., 1976(COULSOY et al., & 1979. Competition occurs as a result of spatial and temporal coincidence in development of both species in the inner bark of the host. Foraging by M. titiltator results in mortality to D. frontalis.(1) Texas Agricultural Experiment Station No. TA15244.

Can. Ent. 110: 471-473 (1978) Xenoborus Reuter is synonymized with Tropidosteptes Uhler. Tropidostepres brooksi n. sp. is described from Saskatchewan, Manitoba, Ontario, and Quebec. The species was collected on Fraxinus spp. Reuter (1908) described Neoborus commissuralis and proposed the subgenus Xenoborus for it. Soon after (1909) he transferred commissuralis to Tropidosteptes Uhler (1 878) and described petitti and plagifer under that genus. Van Duzee (1 9 16a, b ) raised Xenoborus to generic status and transferred commissuralis and plagifer to it respectively. Knight (1917) transferred petitti to Xenoborus and described X. neglectus. Later (1927Later ( , 1929 he added chinaonthi and selectus to it. Xenoborus has retained generic status to the present day.Slater (1950) studied genital structures of Neoborus Distant (1884), Tropidosteptes, and Xenoborus and suggested that the three genera were congeneric. Carvalho (1954) synonymized Neoborus with Tropidosteptes. Kelton (1959) studied the male genital structures of Tropidosteptes, Xenoborus, and Neoborella Knight (1925) and also suggested that the three genera were congeneric. Further studies of the species included in those genera show that Tropidosteptes and Xenoborus are congeneric but Neoborella may be retained as a distinct genus.In addition to the similar structures of the male and female genitalia, species of Tropidosteptes and Xenoborus are also similar in shape and appearance, and all have similar type of habitat. The species are rather large, generally over 5.0 mm in length, elongate and subparallel. The frons are smooth or punctate but not transversely grooved or striate. All are confined to deciduous trees and mostly to Fraxinus spp. The character of the carinate lateral margins of the pronotum used to separate them into two genera is weak and inconsistent. Species in both genera have carinate, partly carinate, or rounded pronotal margins.Although the male genital structures and puncturation on the pronotum in species of Neoborella show a close relationship to those of Tropidosteptes and Xenoborus, species of Neoborella are easily separated from the others by the distinctly grooved and striate frons. They also differ in size and shape. Species of Neoborella are rather small, less than 5.0 mm in length, and oval or oblong in shape. So far as is known species of Neoborella are confined to dwarf mistletoe growing on conifers.Herewith Xenoborus Reuter is synonymized with Tropidosteptes Uhler, and Neoborella Knight is retained as a distinct genus. A new species belonging to Tropidosteptes is described, and illustrated.

Within-tree colonization by Dendroctonus frontalis infesting loblolly pine, Pinus taeda L., was investigated. Two components of the colonization process were studied: the establishment of attacking adults (ATK) and the ensuing construction of egg galleries (GL). Data on the two variables were taken from standing trees beginning at the time of initial attack and continuing for 14 consecutive days.The spatial and temporal sequence of ATK was described for 1.5 m intervals along the infested bole for the duration of the process. A three parameter nonlinear function was used to describe the data. The pattern of attack was also described as an average process for the entire tree using the same model. A frequency histogram encompassing the range in variation for peak ATK from 134 trees was prepared to provide starting values for simulation purposes.The spatial and temporal sequence of GL construction was described using essentially the same approach as employed for ATK. The modeling process was complicated by loss or obscuring of GL from the radiograph by omission errors and foraging by Monochamus spp. and other associates. GL construction was also described as an average function for the entire tree and the rate of GL construction was defined. A frequency histogram of peak GL was prepared from data on 54 trees for use in selecting starting values for simulation purposes.Numerical relationships between ATK and GL were defined by combining the data on ATK and cumulative expected GL.

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