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!
Jeff Tomberlin, PhD, Blow Fly Person Too!
I have been a bit slow with new posts; however, I am truly dependent on those conducting research. So I encourage all of you researchers to publish, publish, publish on the black soldier fly! The blog is dependent on you (small amount of joking with you).
The article to be reviewed today is hot off the press. I do not believe I have reviewed this one before as it is new. If I have - my apologies... but maybe this is an indication the study is so important a secondary review of it is necessary. :)
Xiao, X., P. Jin, L. Zheng, M. Cai, Z. Yu, J. Yu, and J. Zhang. Effects of black soldier fly (Hermetia illucens) larvae meal protein as a fishmeal replacement on the growth and immune index of yellow catfish (Pelteobagrus fulvidraco). Aquaculture Research: n/a-n/a.
This study, like many others, used black soldier fly larvae as a feed replacement for fish. In this case, yellow catfish were used as the model.
Here are some basic facts from the study design:
What did they find?
So, I conclude from this study, that more evidence has been generated for the use of BSFL as a feed replacement for the aquaculture industry- in this case, yellow catfish.
Trivia Fact: Yellow Catfish can reach 50 pounds (22 kilograms)! That is a very large fish IMO.
In previous posts, we have discussed many abiotic factors that impact BSF growth and production ; however, a new article was just published from a join effort with my colleagues in China (Longyu Zheng & Jibin Zhang). The topic covered was pH.
Ma, J., Y. Lei, K. u. Rehman, Z. Yu, J. Zhang, W. Li, Q. Li, J. K. Tomberlin, and L. Zheng. 2018. Dynamic effects of Initial pH of substrate on biological growth and metamorphosis of black soldier fly (Diptera: Stratiomyidae). Environmental Entomology: nvx186-nvx186.
My first set of comments is with regards to the first author- Junhua Ma. Our first encounters were via email with regards to this study and the resulting publication. However, I had a chance to meet him in person this past year and I made a few observations about him (and maybe myself).
1. He is an undergraduate student!! I was so very impressed with his efforts as a student pursuing his BS degree. To invest the time and produce such a high quality study. His maturity is simply impressive! I hope that there are other undergraduates, or producers, out in the world reading this blog and are inspired to conduct their own research.
2. My second observation? I am getting OLD!!!!! Man- when I met Junhua in person... I thought he was in secondary school!!!
Well- enough about Junhua Ma! He has a bright future in research as he is aiming to pursue his PhD in the USA.
Now- how about his (our) paper? What are the major conclusions?
First- you should recognize their goal was to determine the impact of initial pH (important factor- not long term pH... over time) of diet on larval development. This could be a critical component of any system when you consider if you do single feeding (batch) or continual feeding. With continual feeding, you would be adding food periodically to the larval container- which means the larvae are continuously exposed to a set medium pH. On the other hand, if you do a single feeding system, you would be only exposing them to the medium pH one time and then the larvae would modify the pH to a more optimal condition for them to develop (of course, assuming they can modify the pH).
Second- they determined initial pH did impact larval final weights. For larvae exposed to a slightly acidic diet (6.0), larvae were 23% larger than those reared on a more acidic (pH = 2 or 4).
Third- the same results were determined for prepupae (22% larger on the slightly acidic diet, pH = 6.0 rather than the more acidic medium, pH = 2.0/4.0).
Fourth- pH impacted development with those reared on the slightly acidic diet finishing developing 3 days faster.
Jeffery K Tomberlin, PhD
A New Post to Celebrate the New Year- Different "baits" to Attract and Induce Egg-Laying Behavior of the Black Soldier Fly
Hello Everyone- I hope you all are well and enjoying a wonderful new year!
I believe 2017 was a great year for BSF- the blog has been a lot of fun and a success (averaging 6,000 to 8,000 reads per month)- My hope it is serving a role with the BSF community.
But I am optimistic 2018 will be even better. The frequency of BSF publications is ever increasing- and I will do my best to stay on top of everything and make sure to convey these papers and their major findings to you as quickly as possible.
With that said- a paper that just came out examined different "attractants" for ovipositing (egg-laying) BSF.
Comparison of the performance of different baiting attractants in the egg laying activity of the black soldier fly (Hermetia illucens L.)
This study was conducted by researchers in Kenya (awesome to see such a global effort exploring BSF and its benefits) and published in the Journal of Entomology and Zoology Studies.
Basically, the authors wanted to explore different attractants for ovipositing BSF. They used fish, fruit, cow manure, and frass (larval manure - in this case most likely they used larval frass mixed with digest- distillers’ grains and cookies mixture).
They placed these materials individually in containers and then examined the grams of eggs deposited in egg traps associated with each container.
What did they find?
1. These materials were attractive and adults did lay eggs.
2. Manure had the greatest amount (g) of eggs deposited.
3. Frass was second in terms of attraction
The challenge with these results is the level of variation across treatments. Based on the figure, the level of variation would indicate these resources were equally attractive so concluding one is more attractive than another is difficult.
What this work does demonstrate is the larval substrate does play a role in terms of attracting egg-laying adults. So, if someone wanted to tackle a critical question to BSF mass production- I think this would be a great topic.
Imagine if you could get flies to lay eggs where you wanted... precisely.
Jeffery K Tomberlin, PhD, BSF Egger
Individuals with over 25 years research experience with the black soldier fly. We are passionate about the science behind the black soldier fly and its ability to convert waste to protein.
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