Observations on Two Stem-Boring Coleoptera of Prickly-Ash (Zanthoxylum americanum) in Michigan: Micracis suturalis (Curculionidae: Scolytinae) and Sternidius alpha (Cerambycidae)

The xylophagous scolytine Micracis suturalis LeConte and the cerambycid beetle Sternidius alpha (Say) were reared or collected from trunk sections of prickly-ash, Zanthoxylum americanum Mill., in Ingham County, Michigan during 1986 to 1988. Most M. suturalis gallery systems were initiated by August in host material cut in late May 1987. Micracis suturalis gallery-system density data are presented. No M. suturalis were reared from caged host material one-year after cutting. Sternidius alpha was univoltine, with adults emerging from mid-May to mid-July from host material cut the previous spring. From 1 to 8 S. alpha larvae originated from individual oviposition sites, averaging 3. Larvae tunneled first in the cambial region and then entered the xylem in late summer. Larval and exit hole density data for S. alpha are presented.