Switching Gears- Blow Flies as Recyclers

Blow flies (the metallic flies often associated with decomposing vertebrate remains) conjure up a lot of different images when one thinks of their offspring- maggots. Of course, in most cases these maggots, or larvae, are often associated with putrid remains of decomposing animals. Their presence along with the associated odor (and sound) often is disturbing to most. Those not disturbed are typically entomologists or those with a strong affinity for nature, the macabre, or in our case- recycling wastes to produce protein.

The article to be discussed today is out of a great lab in South Africa- a group well known for their work on waste conversion with insects (congrats on another outstanding paper).

Parry, N. J., E. Pieterse, and C. W. Weldon. 2017. Longevity, fertility and fecundity of adult blow flies (Diptera: Calliphoridae) held at varying densities: Implications for use in bioconversion of waste. Journal of Economic Entomology 110: 2388-2396.
The first thing to note is the group known as blow flies (Diptera: Calliphoridae) is quite diverse. There are species that do all sorts of things besides recycle decomposing animals. Some are known to colonize the living (also known as myiasis), while others colonize snails.  But for the most part- they do colonize decomposing vertebrate remains (Check out this time lapse video on this process).

The second thing to point out is that many of these species- especially those that are being targeted for mass production, are very much dependent on a high protein diet, which is why you see them often associated with vertebrate remains.  

Like with the black soldier fly, how we mass produce these insects in colony is critical- No colony equals no waste management. So in this study, the authors examined the impact of adult population density on longevity and fecundity.  And, they did this for four different species.

They determine optimal density is dependent on the species in question. In other words, do not attempt to apply what you know for one species to another and expect the same results.

They also determined there is a tradeoff between longevity and egg production. This concept has been explored quite a bit in the ecology and evolution literature. Basically- if you have a lot of offspring, you probably will not live as long (from the bug perspective).  Here is a cool paper showing that mating can impact longevity of a female. 

What I appreciate most about the article is their discovery of optimal density for producing viable eggs. This topic is something that just has not been explored as much with the BSF and published. 

I suspect, with the right density (speaking of cages designed to hold 5,000 adults), production could reach 50 g of eggs per day per cage. And, yes- I am speaking of the BSF!

Author

Jeff Tomberlin, PhD, Blow Fly Person Too!
Twitter: @FliesFacility
​Director, EVO Conversion Systems