Asymmetric contests among sawyer beetles (Cerambycidae: Monochamus notatus and Monochamus scutellatus)

Females of both Monochamus scutellatus (Say) and Monochamus notatus Drury (Coleoptera: Cerambycidae) preferred to oviposit in large diameter pine logs. When females of both species were present, oviposition on the largest diameter log by M. scutellatus was much reduced. There were both inter- and intra-specific contests among females, usually over oviposition holes cut by females in the bark. Contests among females occurred disproportionately on the largest logs. Previously inseminated females paired with radiation-sterilized males laid no fertile eggs, supporting the hypothesis that a male is highly likely to fertilize eggs laid by a female with which he is paired. In intraspecific contests among females over oviposition holes and among males over females, a challenger could supplant a resource holder only in an escalated contest. However, in interspecific contests, M. notatus challengers were able to supplant M. scutellatus resource holders without escalation. In both sexes, a contest was more likely to be nonescalated when the resource holder was larger than the challenger. Among males, a larger resource holder was significantly more likely to repel a smaller challenger than was a larger challenger to replace a smaller resource holder.

Survey of Biota Associated with Monochamus (Coleoptera: Cerambycidae) in Maine.

The biota associated with Monochamus species collected in Maine include species of Acarina, Diptera, Hymenoptera and Nematoda, as well as fungal and bacterial pathogens.Mites belonging to seven families and thirteen genera were found in association with the sawyers. Two species were previously unknown and have since been described as the new genus and species Longoseius cuniculus Chant of the family Digamasellidae and the new genus and species Mucroseius monochami Lindquist of the family Blattisocidae. Parasitic diptera belonged to three genera in three different families, and of these one contained a new species, Forcipomyia innom., family Ceratopogonidae, which was found as an intermittent parasite of adult Monochamus notatus and Monochamus scutellatus. This constitutes a new host record for the biting midge family. Only one hymenopterous parasite, a species of Dolichomitus was reared from a sawyer larva. The five genera of nematodes isolated from larvae, pupae, and adults of Monochamus species include specimens of the genus Hexamermis. Parasitism by this group is thought to be unusual because of the relative inaccessibility of the host. Isolates from eight fungal genera were obtained, and strains of Beauveria bassiana, and Isaria farinosa, were shown to be pathogenic. The bacteria isolated from dead sawyers included Aerobacter aerogenes, Bacillus cereus var. mycoides, and one unidentified species. Only the tachinid E. monohammi and the mite Uropoda have been previously reported of the large number of organisms found associated with sawyer beetles in this study. The fungus Beauveria bassiana proved to be the most important biological control agent.

Differential Growth as Evidence of the Relationship of Monochamus notatus (Drury) and M. scutellatus (Say) (Coleoptera: Cerambycidae),

Monochamus notatus (Drury) and M. scutellatus (Say) are both common wood-boring beetles in the coniferous forests of eastern Canada. The two species are usually separated on the basis of colour. The first is dark brown with lighter brown elytra, and is covered with white and brown pubescence, while the second , is typicaliy shining black. The scutellum of each bears a dense white pubescence which, in the case of M. notatus, is divided by a bare median line. Such a line also occurs in M. scutellatus but is usually incomplete. The writer has found that the presence or absence of a fringe of white hair around the compound eye constitutes the most consistent anatomical difference between the two species, it being present only in M. notatus. The elytra of the females of both species are generally marked with elongate spots. Body length is also used to separate the two species, but no clear-cut difference in length ranges occurs; instead, there is considerable overlap.