Numbers
Nearctica lists 4 species.
Identification
Larvae start out covered with a powdery waxy white coating, which they shed later in the year to become yellow with black cross-stripes or spots on top.
--Dave Smith has provided the following information on distinguishing the larvae:--
There are four species of Macremphytus in N. America: M. lovetti is in the Pacific Northwest and BC; M. semicornis in eastern Canada and NE US; and M. testaceus and M. tarsatus both in eastern US and Canada. The larva of M. semicornis is not known. The larva of M. lovetti is very similar to the eastern M. testaceus.
Larvae of the two common eastern species can be separated as follows:
M. tarsatus – both the feeding stages and prepupal stage have a rectangular black mark on each segment.
M. testaceus - the feeding stages are uniformly green (no black marks), though the whitish bloom may make them look white.
Color changes when molting to the prepupal stage; there are black spots on the body (spots, not the rectangular pattern as in tarsatus).
Life Cycle
Larvae bore into wood in fall to pupate and overwinter. In wild conditions this would normally be dead wood on the ground, but they have also adapted to bore into man-made structures. Dave Smith has reared them by giving them corks to bore into.
Remarks
Although many websites refer only to Macremphytus tarsatus, apparently there are 3 spp. that feed on Dogwood, all with similar larvae. See
MSU.edu.
Internet References
Larval image - powdery white immature larva and black and yellow mature larva at Forestrypests.org
