Subject:  Fly identification
Geographic location of the bug:  Idaho
Date: 09/15/2017
Time: 11:16 PM EDT
Dear Mr. Bugman,
I took a photo of a large, mostly black fly with two white dots on the rear part of its abdomen. I have only found the fly outside once. All other flies inside my house are plain black with no white dots. I have attempted to find the type of fly online but with no luck so far. If you know what type it is I’d be very interested to hear. Thank you for your time and help!
How you want your letter signed:  Sincerely, Sarah

Tachinid Fly

Dear Sarah,
This is a parasitoid Tachinid Fly, and according to BugGuide, there are  “1350 spp. in >300 genera of 4 subfamilies in our area [North America].”  We quickly scanned BugGuide down to the tribe level and could not locate this particular species.  Tachinid Flies are important biological control agents against other insects and arthropods, and according to BugGuide:  “Larval stages are parasitoids of other arthropods; hosts include members of 11 insect orders, centipedes, spiders, and scorpions. Some tachinids are very host-specific, others parasitize a wide variety of hosts. The most common hosts are caterpillars. Most tachinids deposit their eggs directly on the body of their host, and it is not uncommon to see caterpillars with several tachinid eggs on them. Upon hatching the larva usually burrows into its host and feeds internally. Full-grown larva leaves the host and pupates nearby.”  If time permits, we will try to identify your Tachinid Fly to the species level, but now you also know where to do the research.  If you find a visual match, please let us know.

Location: Idaho

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