Huge Black Fly for ID …
Location: Applewood, Golden, Colorado
July 24, 2011 7:36 pm
Great site you have here! My daughter and I caught this huge black fly in our back yard today, and she would like to know what kind it is.
It is very large (as far as houseflies go), and has a tan / grey area on its back, and also leg joints of the same color.
I tried to get a good picture of its eyes as well, as thet are quite stunning, with horizontal stripes accross them. I could not get an image that did them justice.
Thank you for your time,
Charley and Hannah
Signature: Charley and Hannah
Dear Charley and Hannah,
You have captured a female Western Horse Fly, Tabanus punctifer. The female can be differentiated from the male by the spacing between the eyes. There is space between the eyes of the female but the males eyes meet in the middle. Female Western Horse Flies are blood suckers that feed on warm blooded animals. If livestock and game are not available, they will bite humans.
Thank you so much for the speedy reply. It really made Hannah’s day!
Here is the drawing that she made to save for her bug journal.
We catch, study and release a lot of Swallow Tail Butterflies in our back yard too (see second pic). Is there a similar trick to determining the sex of that species?