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Photo#323896
Cuterebra emasculator

Cuterebra emasculator
Kingston, New Hampshire, USA
August 1, 2009
Found near an old gravel pit adjacent to a large wetland area.

What's in a name
Beautiful fly! I came across an explaination for how bot flies got the emasculator epithet. According to Metcalf in "Destructive and Useful Insects" (1962) they have been found in squirrel testicles, and were presumed to emasculate the poor host.

 
emasculator
Hi Mark,
The bots are in and around the groin, but lucky for the chipmunks they don't actually emasculate the host (as Fitch described in 1856 and Dury also promoted in 1898). This was a myth for a long time. Earnest Thomas Seton tried to question the myth in 1920 but it lived on. It does look nasty, and can't feel great with a maggot (or two or three) near your privates. But the testes are withdrawn into the abdomen during bot season, so it simply appears as if the bot has replaced the testes. The chipmunks go back to breeding once its over in about a month. (For chipmunks the bots enter after breeding season anyway-- at least in the north, with lots of time to recover). So bots are pretty well evolved to not impact the host. Recent authors have found no evidence for emasculation ( Bennett 1955, Siegmund 1964, Timm and Lee 1981 and 1982 and others).
Although... I have seen Peromyscus with nine C. fontinella at one time and they could barely walk, so when a heavy bot year they may make some individuals more likely to be caught by predators. But they can handle one or two bots with little or no impact. I have also removed one bot from a female mouse, which was preventing her from giving birth. But complications like this are rare.
If the animal allows the bot to develop and come out naturally, the wound heals very quickly. I have pulled bots ready to emerge from mice, and then caught the mouse again the next several days, and within about 2 days the wound looks like it had been stitched by a doctor, and a few days later it is hard to even find the wound. Some people think their may be special antibiotic and or healing properties in bots, because the wounds heal so fast. It is to the bots advantage not to hurt the host, as its offspring can use the same host the following years. Emasculating the host would also collapse chipmunk populations, which tend to breed only once in the north in most years. I have seen years with 80% infection rates, so this would put a lot of pressure on chipmunks if breeding came to a halt. Chipmunks tend to live a long time and defend territories so it would be hard for populations to recover if all of these were emasculated. So by not doing serious damage, C. emasculator ends up not doing a whole lot to impact chipmunk populations.
Thanks for the post. Hope this clears some things up. Still a great name.
Jeff

Cuterebra emasculator
Thanks so much for posting this one Dave! As Eric mentioned we have not had this one show up on BugGuide yet! It is for sure C. emasculator, although a horrible name since they generally do not harm the host and do not emasculate them! This is our only golden haired bot in the Northeast and this species can be found anywhere east of the Mississippi although rarely seen. It is primarily host specific in the Northeast on chipmunks, Tamias striatus, however it uses mostly Sciurus (gray and fox squirrels) in the south. These may turn out to be two species of bots when dna is examined? Sabrosky (1986) could not seperate them into two species by outward characteristics. But considering this fly is common in chipmunks in the Quabbin where my crews have handled 34,000 small mammals -and yet we have never found the species in any grey squirrel or southern flying squirrel- hints that this species could be very host specific.
If anyone finds this species in the south and can send me a specimen I would be interested in doing some dna work on this one. Especially interested in bots pulled from a known host, road kill and pet killed specimens with known host records would be great.
Jeff

Moved
Moved from ID Request.

Cool!
New species. Thanks for posting!

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