Subject: Insect all over Cedar trees
Location: Castleford, Idaho
October 10, 2016 4:45 pm
It appears to be boring into the trees and causing damage
Signature: ??



This is a Horntail in the family Siricidae, and probably in the subfamily Siricinae, the subfamily that feeds on conifers.  Horntails are non-stinging relatives of Wasps, and they have larvae that bore in wood.  This female is likely in the process of laying eggs.  She looks like she might be Sirex nigricornis, a species pictured on BugGuide.  Though there are only a few images posted to BugGuide and they are from Pennsylvania and New York, the range, according to BugGuide, is “across Canada (QC-AB-?BC) and the US south to FL-TX” and “wide host range, mostly on various pines.”

Location: Castleford, Idaho

2 Responses to Horntail

  1. Martin says:

    Do you know if it repopulates quickly? I recently came back from a wedding in Montana and passed through Idaho on my way back. Somehow, we found maybe 4 of these guys in our car when we got home in Oregon. We killed them immediately, but just hope they haven’t started to reproduce

    • bugman says:

      We believe we have read that the life cycle takes several years. According to BugGuide: “larval development may take 1 to 3 years to complete depending on species and climate.” Based on what we know about the climate of Montana, we are guessing that the cold winters would extend the larval stage to the three year span. According to Bug Eric: “It usually takes more than one year for the horntail to complete metamorphosis.”

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