Farming BSF | General Guidelines that Work Well in Propagating BSF Larvae : The Life and Times of BSF (Black Soldier Flies)
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Farming BSF | General Guidelines that Work Well in Propagating BSF Larvae

by Terry Green on 03/10/16

In an earlier blog I described a simple technique for scaling up propagation of BSF using leachate recovered from food scrap and larvae mixed with leftover puparia shells (see Farming BSF | Propagating Larvae Simply and Economically). If you don’t have access to puparia shells, there are a number of other simple and inexpensive methods of propagating BSF. This blog describes the essential steps in achieving consistent and reliable results in maximizing the recovery of viable larvae.

From a business perspective there is a significant advantage in keeping propagation costs low and the recovery of viable larvae high. Although there are certain situations where the investment and construction of a separate BSF nursery may be preferable, if the principal goal is solely on scaling up larval production, setting up a separate more costly and labor intensive insect nursery unit is not necessary.

Adult female BSF looking for a site to deposit their eggs are attracted to the odor of decaying (putrescent) waste, especially waste wetted with residue and/or liquid on which larvae have previously fed. To attract female BSF to putrescent waste set out for the purpose of amplifying larval production, pay attention to the following guidelines:

  • Deposit the putrescent waste (the “attractant”) within a shallow breeding container constructed with access holes for female adults to crawl inside;
  • Layer the attractant on the floor of the container at a depth of not more than about 0.2 to about 0.5 inches (~ 0.5 to 1.3 cm);
  • Keep the container holding the attractant free of sporulating fungi which if present will quickly kill any eggs laid by the female inside the container;
  • Ensure that the attractant does not dry out by adding water as necessary to keep it moist; and
  • See that these operations are done in a place within a temperature range of anywhere from approximately 72 to 105 F ( ~22 to 40 C) for best results.
Since mating conditions for BSF are similarly ideal conditions for propagating new larvae, place breeding containers prepared with attractant in the same area where BSF are mating. After mating, females will find their way into the containers where they will deposit fertile eggs, usually around the inside perimeter of the container, but also not uncommonly around the top edges of the container (see Fig. 1).
image of BSF egg-laying larval propagating and hatching unit
Fig. 1. Top-down view of an egg-laying larval hatching and breeding unit constructed from a recycled plastic coffee modified for propagating BSF larvae. The lid is set to the side revealing large numbers of eggs deposited by female adults around the inside perimeter of the lid. Holes (~0.75 inches in diameter) allow females to enter the unit and lay their eggs from which new larvae soon emerge within a matter of a few days. Adult females can be seen crawling over the attractant (wheat bran + BSF leachate) layered on the floor of the unit. Units can be stacked on shelves in rows and layers in various staggered configurations that take up little space. Copyright © 2016 Terry Green, All rights reserved.

The advantage of this simple hands-free technique in propagating BSF larvae is that it is inexpensive and effective, it completely eliminates the necessity of transferring eggs laid by females to another breeding unit, reducing in one single step the labor otherwise required in harvesting and transferring eggs to another growth medium and, at the same time, increases the yield of larvae with less damage to eggs incurred when eggs are transferred from one medium to another.

Fig. 2 shows how wheat bran wetted with BSF leachate makes a very effective egg-laying attractant in propagating young BSF larvae in this manner. The shape of the breeding container is unimportant. Holes big enough for females to crawl inside the container (located preferably in the lid of the container) should be not less than approximately 0.5 inches ( ~1.3 cm), or greater than about 1 inch (~2.5 cm).

Image of elements needed in operating a BSF larval propagating unit

Fig. 2. Fundamental elements making up a simple hands-free BSF larval propagating unit. Upper Left, an assembled egg-laying larval hatching unit fabricated out of recycled plastic coffee can (note snap on lid with holes in top which allow BSF adult females to enter the unit and deposit egg clutches inside the hatching unit). Upper Right, whole wheat bran which provides nutrients necessary in supporting the initial growth of newly hatched larvae pending transfer to a BSF bioreactor; Lower Left, BSF leachate recovered from a BSF bioreactor used in wetting the wheat bran in rendering it an attractant to BSF egg-laying female adults; Lower Right, Several thousand newly hatched BSF larvae growing in the attractant waste ready for seeding a BSF waste processing bioreactor. Copyright © 2016 Terry Green, All rights reserved.

Once young larvae are seen growing in the attractant, seed the newly hatched larvae into a larval bioreactor by flipping the container upside down over the waste to be processed in the bioreactor.  Refill the egg-laying unit with a fresh layer of egg-laying attractant so as to draw more egg laying females into the container, and continue in this manner “round-robin” in building up the larval population in your larval bioreactors.

The lids and breeding containers can be intermittently rinsed as needed in water to clear them of fungal spores. Plastic breeding containers work best since they are easy to clean, light weight, and because they can be easily fabricated from common materials readily available for little or no cost.

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Comments (2)

1. Angie Bowers said on 5/12/16 - 03:21AM
I live in an area with very limited heat and sunlight most of the year. Are there certain bulbs that will work to stimulate mating?
2. Terry Green said on 5/14/16 - 09:27AM
Angie, there has been some limited work done on artificial lighting in rearing BSF larvae indoors. J. Zhang et al. published a study claiming success in inducing BSF adults to mate and oviposit fertile eggs (see “An Artificial Light Source Influences Mating and Oviposition of Black Soldier Flies, Hermetia illucens”, The optimal wavelength appears to be in the visible spectrum between 450 and 700 nm. Light intensity also appears to be of significance. More frequent mating appears to be associated with higher intensity lighting approaching that measured in sunlight. Zhang et al. found the best results with halogen (quartz iodine) lamps although mating was not as good as occurs in natural sunlight. CFL (compact fluorescent light) has a similar visible spectrum but are of much lower light intensity.

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