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

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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.