Farming BSF | Propagating Larvae Simply and Economicallyby Terry Green on 08/21/15
There is growing interest in the potential opportunity of commercially farming and harvesting Black Soldier fly (BSF) larvae as efficient and environmentally beneficial recyclers of waste, and as alternative high quality animal feedstocks, even though much work and research remains to be done for this goal to become a viable option (see Black Soldier Flies as Recyclers of Waste and Possible Livestock Feed). Farming BSF successfully on a commercial scale of any significance will depend very much on yields realized. It is known that larval yields harvested from food scrap, an abundant source of waste, depends principally upon the waste load rate (WLR) and waste processing footprint (see Scaling Up BSF Production | Theoretical and Practical Effect of BSF Bin Space Surface Area and Food Scrap Load Rate on Larval Yield). Other variables affecting the yield of larvae grown from waste include the average daily larval population feeding on the waste, and the nutritional quality of the waste. Larvae grow better and faster on food waste richer in nutritive value relative to animal manures, for example. This blog describes how to setup a simple and economical method for propagating larvae concerning scaling up BSF yields.
To better understand how the average daily population of larvae housed in a waste processing bin or trough affects harvest yield, consider what happens as the larval population increases. If you were to double the average number of larvae in your waste processing site, for example, you would realize a proportionate increase in the turnover rate of waste processed by the larvae, and a corresponding increase in larval yield accompanying the increase in the WLR made possible by increasing the number of larvae feeding and growing off of the waste. This underscores why it is important to maintain as high of a population of larvae as practical in maximizing larval yield.
BSF female adults, attracted to decaying waste, are not particularly adept in ensuring that their egg clutches are best positioned for the survival of new larvae emerging from the eggs they lay. They waste a lot of egg clutches depositing their fertilized eggs near but not in optimal locations that would ensure that all newborn larvae successfully find their way into waste processing bins and troughs used in farming BSF. Egg clutches laid too far away not uncommonly become desiccated before hatching. Eggs left in the open also occasionally become contaminated with fungi which destroy the eggs before larvae are able to hatch and crawl free from the egg clutches. These scenarios left unchecked markedly reduce the efficiency of a farming operation.
It is feasible however to entice adult female BSF to deposit their egg clutches in large numbers in confined egg incubator/hatching units, easily managed, readily available and assembled from discarded plastic food containers, which, after assembly, serve as protective incubators and hatcheries. Setting up a system for capturing larval eggs more efficiently and safeguarding newly hatched larvae from fungi and other predators pending their transfer to waste bins and troughs greatly improves the efficiency of the farming operation.
Larvae recovered using these units can be easily transferred to waste processing bins and troughs at will “round-robin” in ramping up the number of larvae processing and growing off of the waste.
There are biological constraints limiting the practicality of increasing the larval population at a processing site above specific thresholds dependent upon the source of the waste, the temperature of the waste as it decays, its water content, and a variety of other complex variables. Nevertheless, if as noted earlier the WLR can be doubled, or even tripled, by increasing the average larval numbers processing waste proportionately, the footprint required in processing and harvesting larvae can be correspondingly reduced resulting in a savings in upfront capital outlay in building a processing site. Increasing the average daily larval harvest rate furthermore provides more income in offsetting the cost of farming BSF. Maximizing the average daily population of larvae growing off of waste in farming BSF is consequently quite important in achieving a viable operation that will pay for itself over the long haul.
Assembling egg incubator/larval hatchery units can be done simply and inexpensively. One can use discarded retail plastic ~34 Oz (~960 g) coffee cans, for example, which can be stacked on shelves in proximity to mating BSF that are also easily cleaned and recycled as needed. Such collection units are accepted very well by female adult BSF looking for a safe place to deposit their egg clutches.
The lids to the recycled plastic cans should be retained as well and serve to retain moisture inside the units which reduces the prospect of eggs desiccating in addition help contain newly hatched larvae inside the assembled units pending their transfer to waste bins and troughs where they will be grown and harvested. Lids that come with the discarded coffee cans can be snapped over the top of the cans also providing a perfect hidden enclosure for adult females seeking a convenient site for laying their eggs.
To provide female adults access to the assembled units, drill two to three holes in the lid approximately ¾ inches (~1.9 cm) in diameter spaced evenly around the center sections of the lid (Fig. 1). Adult females fly or crawl inside the units through the holes in the lids and tend to deposit their egg clutches in large numbers on the underside of the lids where the lids abut the edges of the discarded coffee cans.
Fig. 1. Picture of an assembled BSF egg incubator/larval hatchery unit assembled from a discarded plastic coffee can. Holes in the upper lid allow adult female BSF access to the unit.
To attract female BSF to the egg incubator/hatchery units, add a layer of empty larval puparia shells mixed with BSF/food scrap leachate (see Soldier Fly Food Scrap Leachate | A Treasure Trove Amended in Soil). A small amount of food scrap should also be placed on top of the empty puparia shells (see Fig. 2) to support growth of newly hatched larvae pending follow-up transfer of the new larvae collected in this manner to larger bins and troughs where harvesting of prepupae subsequently occurs.
Fig. 2. View of interior of BSF egg incubator/hatchery unit showing appearance of prepupae shells wetted with BSF leachate obtained from BSF processed waste which in combination with a small amount of food scrap serves to attract egg laying female adults inside the unit. Females deposit egg clutches principally on the upper inside lid of the unit (not shown).
Figs. 3, 4 and 5, show pictures of typical egg clutches deposited on the underside of the lid of an egg incubator/hatchery unit, and subsequent hatching and confinement of newly hatched larvae, respectively, inside the units. The deposition of eggs in the units usually occurs in one to two days of setting the units out where females have access to the units.
Female adults are strongly attracted to the combination of pupae shells and BSF leachate. They land and crawl around the top edges and inside the units, and lay eggs around the outer edges of the lids (Fig. 3).
Fig. 3 Image of many thousands of BSF eggs deposited by adult female BSF on the underside of an assembled egg incubator/hatching unit using BSF puparia weted with BSF processed food scrap leachate as an attractant and a small piece of food scrap set aside for sustaining the growth of newly hatched larvae.
Newly hatched larvae can be retained in the units (see Figs. 4 and 5) until subsequently transferred to larger waste bins and troughs. Egg incubator/hatchery units should be routinely emptied into larger bins and troughs “round robin” as soon as the larvae have all emerged from egg clutches left around the edges of the lids, in this manner serving to boost the average daily population of larvae in the larger bins and troughs.
Each incubator/hatching unit houses upwards of several thousand newly hatched larvae. Units can be loaded and emptied on a continuous basis, making it feasible to ramp up and sustain a large scale and continuous stream of new feeder larvae as needed in sustaining the farming operation.
Fig. 4. Image of newly hatched BSF larvae crawling around on lid of egg incubator/hatching unit ready to be transferred to scale-up waste processing food scrap bins and troughs.
Fig. 5. Image of newly hatched BSF larvae hatched in egg incubator/hatching unit ready from transfer to scale-up waste bins and troughs. The incubator/hatching unit holds several thousands of newly hatched larvae, many feeding on residue left behind and buried along with puparia at the bottom of the unit.
Check back for more to follow on the management and strategies in farming BSF. Comments on this blog, or any of our other blogs, are always welcome. Follow us through our RSS feed. For additional information or follow-up questions, visit our Q&A's or Forums page, or Contact Us (http://www.dipterra.com/).