Black Soldier Fly- Forensic Friend & Environmentalist

First- A Warning- this post contains a bit graphic information about death investigations and the use of the BSF as evidence.

But, if you trust me, and read the post, you will see how this topic relates to the BSF and its use in recycling nutrients.

My hope is I demonstrate how research in what appears to be completely disparate fields has relevance to the use of BSF for recycling nutrients. And, with that said, I encourage you to think outside the box- don't restrict yourself to entomology or BSF production. Always think- how can I apply what I learn about something completely separated from BSF... to BSF. Anyway, I hope you enjoy. :)

So... here is my official daily post! 

Today, I found myself sitting back and relaxing in my room after a long day working in China- thinking about what we know about the BSF and where the "holes" in its biology are present. You should know, I often find myself thinking about this topic- sort of an obsession for me. ;) 

Some of these voids are quite visible (e.g., adult biology is massively under-studied), while others seem to become more clear, or become recognizable, with each publication, post on Facebook, and completion of a side project carried out in someone's backyard (I cannot understate the value of the work others do primarily because of their passion or interest [researcher, environmentalist, conservationist] in BSF- please, keep up the great work and talk about it with others on Facebook or other similar platforms).

Again... I digress- back on topic!

Well- I was thinking today about the overlap between BSF as an environmental tool and its use as evidence in forensic investigations. Yes- you read correctly... forensic investigations.  For those that did not know, I am a board certified forensic entomologist. I have assisted with over 110 investigations from across the USA.

www.forensicentomologist.org

So, I thought I would provide a little background on this topic and link it back to the use of the BSF for recycling food or animal waste.

Forensic entomology can be defined as the use of arthropod evidence in criminal investigations. There are three sub-disciplines; 1) urban (insects in your home- e.g., termites/ants), 2) stored products (e.g., beetles infesting your flour), and 3) medico-legal entomology.  The primary focus of this post is the third topic- medico-legal.

www.forensicentomology.com/definition.htm

There are a number of ways arthropods can be used as evidence in criminal investigations (primarily neglect/abuse and/or death investigations).  Here are some of the major categories:

1. Time of Death- in many instances, insects colonize human remains soon after death. Thus, if you can determine when colonization occurred, you can potentially infer when the person died. Of course, that is dependent on a number of assumptions, such as colonization actually occurred after death.

2. Movement of remains- insect communities found in one area can be quite unique from another. Thus, if remains are moved from one location to another, differences in insect communities on remains could be indicative of such events taking place.

3. DNA evidence- insects feeding on human remains ingest the host DNA. So, even if the body is moved, DNA of the victim can be secured if larvae that were feeding on the body are still present.

4. Entomotoxicology- insects are what they eat. If insects are feeding on tissue contaminated with narcotics, those narcotics will impact the development of the insect. Furthermore, the insects will potentially bioaccumulate the narcotic, or its derivatives, in its fat body. So, toxicology analysis can be used to determine if narcotics were used prior to death.

Because the BSF will colonize a variety of decomposing materials, including human remains, it is considered an insect of forensic importance.

The first major study relating this insect to forensics was published in the mid-1990s.

Lord, W. D., M. L. Goff, T. R. Adkins, and N. H. Haskell. 1994. The black soldier fly Hermetia illucens (Diptera: Stratiomyidae) as a potential measure of human postmortem interval: observations and case histories. Journal of Forensic Sciences 39: 215-222.

The article is difficult to locate (restricted access); however, if you are interested in learning more about the field of forensic entomology, you might read this book as it gives an overview of the topic as well as mentions this particular study.

books.google.com/books?id=DAa0BzT7Mf0C&pg=PA215&lpg=PA215&dq=black+soldier+fly+forensic+entomology+Lord+1994&source=bl&ots=JzoAvmizmw&sig=4pA_ei8Pdj-VRawuRa_qCK4cmFc&hl=en&sa=X&ved=0ahUKEwjt-tOIvcLWAhUDTCYKHaqiCHQQ6AEIVzAO#v=onepage&q=black%20soldier%20fly%20forensic%20entomology%20Lord%201994&f=false

The interesting find in this study is the authors hypothesized the BSF colonizes decomposing vertebrate remains 20-30 days after death of the individual. This information proves critical when determining time of death. By estimating colonization occurred 20-30 days after death- the estimate, based on age of the insect, will be extended back several weeks.  

However, this conclusion did not prove to be universal.

A subsequent study by yours truly, determined this information to be... well, possibly not correct under all circumstances.

citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.546.4984&rep=rep1&type=pdf

The study I published was from my time as a PhD student at the University of Georgia. I did a project examining insect colonization patterns of swine remains and determined the black soldier fly will colonize within SIX DAYS after death of the animal. This discovery was a major shift in our understanding of BSF biology (remember, previous study said 20-30 days). So, because of the study I published, and it being in conflict with the previous study, forensic entomologists are extremely careful with drawing conclusions on time of death based on this particular insect.

Another study recently published also indicated the BSF has a very slow development when fed animal tissue, and this might explain why the first study concluded colonization had to be 20-30 days after death.

Basically, BSF in the first study were feeding on vertebrate tissue- something that suppresses their development extensively. Basically, the second study concluded colonization in the first most likely occurred soon after death of the victim; however, the insect just needed a lot more time to complete development.

Here is the paper- if you would like to read it.

www.sciencedirect.com/science/article/pii/S0379073816302092

This information is critical for forensic entomology as the studies demonstrate two key factors impacting development, 1) temperature (from the second study), and 2) resource type (first and second studies).  Understanding both are essential for applications in the field of forensic entomology.

But what does this have to do with nutrient recycling? First, if you made it this far in the blog post- congratulations!! :)  I see you are not easily swayed from reading about the BSF.

Second- good question! These factors demonstrate the BSF is not like most other flies. They can take months to develop while most other flies develop in a few weeks. This information is critical for mass-production of the BSF. You will find I often discuss these factors with regards to BSF production. Even when discussing other abiotic or biotic conditions- nutrition ecology as related to temperature will probably make an appearance.

Here is a cool link if you want to read a bit more about nutrition ecology:

www.nutritionecology.org/overview/nutrition_intro.html

But.... as far as this post... the take home message is this....

If you are wanting to harvest larvae in an efficient manner- you really need to be conscientious of these two factors as they can truly disrupt your production. 

As always, I hope you find this information interesting and helpful- until next time, best of luck and happy BSF farming!!

Author

Jeff Tomberlin, PhD, D-ABFE
Twitter: @FliesFacility
Director, EVO Conversion Systems
​evoconsys.com