Subject: Large fly and spider
Location: New Hampshire
November 14, 2015 7:35 pm
I was camping in New Hampshire in the white mountains area. These two cuties were with us. One as a dinner guest and the other after a rain storm. Please help. I’m good at identifying most bugs (I actually wanted to be an entomologist ) but I was surprised by them.
Signature: Eric Barbasso
Your spider is one of the Orbweavers, and your large fly is a Rodent Bot Fly in the genus Cuterebra. According to BugGuide: “Females typically deposit eggs in the burrows and “runs” of rodent or rabbit hosts. A warm body passing by the eggs causes them to hatch almost instantly and the larvae glom onto the host. The larvae are subcutaneous (under the skin) parasites of the host. Their presence is easily detected as a tumor-like bulge, often in the throat or neck or flanks of the host. The larvae breathe by everting the anal spiracles out a hole (so they are oriented head-down inside the host). They feed on the flesh of the host, but only rarely does the host die as a result.” We believe your Bot Fly is Cuterebra fontinella fontinella, and according to Bugguide: “White-footed mice (Peromyscus leucopus) are the main host for this subspecies.”
Thanks for getting back to me. That’s what I thought as far the spider was concered. But, to know we have Bot Flys here is scary.
Hi again Eric,
Though sightings of adult Rodent Bot Flies are not that frequent, based on the number of rodents with bots, they are not rare, and they are no cause for alarm. The bots are not especially detrimental to the rodents and the Bot Flies do not trouble humans.