Mexican Cactus Fly

Large Deep Blue flying insect
October 11, 2009
I saw this gorgeous thing here in Souther California on the first of October this year. It is over an inch long with a heavy body, fast flyer and able to hover easily although it didn’t stay still for very long.
Any Ideas?
Mark Houck
High in Beverly Hills, Los Angeles, California

Mexican Cactus Fly
Mexican Cactus Fly

Hi Mark,
Your photos don’t have the necessary details to make any identification a certainty, however, since we also live in the Los Angeles area and we have seen the Mexican Cactus Fly, Copestylum mexicanum, in our own garden, we are guessing that it is probably the insect you photographed.  The Mexican Cactus Fly is one of the Flower Flies or Hover Flies in the family Syrphidae.  According to Charles Hogue in his book Insects of the Los Angeles Basin:  “This is a giant member of the flower fly family (its body length is 5/8 to 3/4 in, or 15 to 20 mm), with a shiny smooth purplish-black body.”  Hogue also writes:  “the larvae are large … pale cylindrical maggots that feed in the rotting, soupy interior of dead and decaying tissues of cacti.”  You may also see numerous images of stationery specimens posted to BugGuide.

Mexican Cactus Fly
Mexican Cactus Fly

Many thanks. The insect I saw seemed to have a brighter coloring, but everything else looks the same.
Wow- they’re big!
Thanks again.


Photo of author


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