- Common Name(s): Bottle Fly, Blow Fly, Carrion Fly
- Order: Diptera
- Family: Calliphoridae
- Common Species: Lucilia spp., Calliphora spp.
- Commonly Confused With: House Flies
How to Identify?
Blow fly adults are a metallic green, blue, copper, copper-green, or dark blue/green almost black color. The larva is a white or yellowish color and grow larger the more mature they are (these ‘levels’ of maturity are called instars). Pupa is generally a tan or brown color but is not commonly found. Fly identification can be hard without getting too technical or scientific so, if you want to be sure about your identification, capture a specimen and consult an Active professional or a University for identification help!
Where do they live?
As juveniles, blow flies live in carrion, feces, rubbish, other rotting garbage, or some other host (screwworms, which are a type of blow fly, prefer to use living hosts). They then crawl to the soil to burrow and become a pupa (resting stage between juvenile and adult flies), and later emerge as adults. Adults are commonly seen around trash cans, excrement piles, or dead animals because this is where they like to lay their eggs. Adult blow flies will bathe in the sunlight on the sides of homes or other safe areas.
What do they eat?
The larval stages (juveniles) feed on the feces, garbage, carrion, etc. on which they are laid. Pupae and eggs do not need to eat. Adults can eat a variety of different things, but their feeding is not what makes them a nuisance. It is their search for an adequate spot on which to lay their eggs that can make them annoying for homeowners.
What do they do?
These insects are not pests in the way you might think. Since they live on rotting, decaying, or other filthy matter they can be an indicator that you might have a dead animal around, which would definitely be a good thing to know! They are also very beneficial in forensic entomology to help determine the time of death (Post Mortem Interval). However, since they have such an affinity for nasty or unsanitary areas, they can mechanically vector a ton of viruses, bacteria, and other pathogens. Mechanically vectored diseases are spread by contact: a fly lands on poop, picks up bacteria on its body, lands on your food, bacteria is transferred to your food by the fly; mosquitoes transfer viruses, bacteria, etc. through a bite, which makes them chemical vectors.
There is actually a type of blow fly called a screwworm (Cochliomyia Hominivorax) that can affect cattle and other livestock through a process called myiasis (the fly larva will burrow under the skin to feed and grow). Visit https://www.cdc.gov/parasites/myiasis/faqs.html for more info on myiasis! There is also a process called “maggot therapy” which the University of Florida website: http://entnemdept.ufl.edu/creatures/livestock/flies/lucilia_sericata.htm covers more in depth. I won’t go into detail here, but if you have a strong stomach and are not afraid of insects it is an amazing process to read about!
Author: G. Wyatt West– B.S.E.S University of Georgia 2017; Board Certified Entomologist
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