The business of breeding insects

Why breed insects?

“If you’re investigating integrated control measures, you need insects for testing,” says Dr Des Conlong, an Extraordinary Professor in the Department of Conservation Biology and Entomology at Stellenbosch University (SU).

Besides research, pest insects are needed for propagating natural enemies and developing and implementing sterile insect technique. Conlong has been involved in developing sterile insect technique for sugar cane borers and is currently establishing a research colony of macadamia nut borers (both are moths).

Hortgro’s bespoke phytosanitary research facility, PHYLA, employs insects for testing and validating postharvest control measures, so the PHYLA insectary is crucial for gaining and maintaining market access.

“Insects are also reared on a large scale for the production of high-value compounds, such as chitosan and melanin,” says Dr Elsje Pieterse, senior lecturer in the Department of Animal Sciences at SU. “Sometimes the main goal is to get rid of waste.”

Waste-combating soldiers

Black soldier flies are remarkable animals. Their larvae weigh a mere 0.2 mg at hatching but can increase their mass by 550-fold within six weeks. To put this in perspective, a broiler chicken increases its mass about 70-fold over the same period.

So, black soldier flies clearly have an edge when it comes to growth. But why would anyone want to grow them?

“South Africa is transitioning to zero waste to landfill,” says Pieterse. “This means the large food chains will no longer be able to send, for example, products past their sell-by dates or that have been exposed to cold-chain breaks, to landfill.”

Fortunately, black soldier fly larvae will eat almost anything humans eat (except margarine), turning food waste into useful products within five days.

“For every tonne of food waste we feed the insects, we can reclaim up to 600 litres of clean water. We can also potentially scrub out and reuse the ammonia and carbon dioxide they produce,” says Pieterse. “Everything in the system can be recycled.”

The larvae themselves are fractionated into chitin, melanin, fats, and protein. “The main fatty acid in black soldier fly larvae is lauric acid, which is the same fatty acid found in palm and coconut oil,” adds Pieterse. “Producing it from insects is completely sustainable.”

Lauric acid is mainly used to make soaps and cosmetics. Chitin and melanin have a wide range of applications, including in the pharmaceutical, medical, and bioremediation industries. Even the insect excreta have value: frass is an ideal substrate for biogas production.

Catering for insects

At PHYLA, Stenekamp frequently faces new catering conundrums. Most recently, she collected bryobia mites to establish a colony, but needed to figure out what to feed them, since giving them leaves from commercial orchards risks exposing them to predators or pesticides.

“The common method of breeding mites is to keep them on plants,” says Stenekamp. “Depending on the mite species, you can use bean seedlings.”

According to Conlong, it helps to start insects on their natural host. “Then you can try and develop artificial diets through analysis of the host plant,” he says. Besides being potentially safer, artificial diets are more convenient and cost-effective.

As an animal scientist, Pieterse uses the opposite approach. Rather than analysing the host, she analyses the insect to determine its amino-acid profile. She then systematically tests different feed formulations to discover the optimal amino-acid, energy, vitamin, and mineral levels for that insect species.

“Some of the vitamins and minerals we would usually give to humans and other vertebrates are deadly to insects,” she says. “On the other hand, insects generally need aldehydes. Some people think the formaldehyde in insect feeds is a preservative, but it’s actually included as a nutrient source.”

When formulating diets for mass rearing, Pieterse distinguishes insects that feed in a substrate, such as black soldier fly and false codling moth larvae, from those that feed on a substrate, such as crickets and cockroaches. The latter are easier to feed because the food’s structure isn’t important.

For insects that live inside their feed, structure is a matter of life and death. “The moisture in the feed must be bound. Insects aren’t fish – if you have free water, they drown,” says Pieterse. “Free water also cools the feed through evaporation, and the insects need warmth to eat and grow.”

Tricky species

Thriving colonies need insects that breed, but the invertebrates don’t always cooperate. “Sometimes they won’t mate or lay eggs, so you must try to see what’s bothering them,” says Stenekamp. “We’ve had species that won’t lay eggs in the laboratory because they need natural light.”

Conlong recalls breeding a particularly idiosyncratic fly species. “We had to put a newly emerged female and a three-day-old male in a test tube, and then stand in the sun, and shake them until the male was ready to mate with the female,” he says.

Black soldier flies breed relatively freely, but optimising their production has commonalities with pome and stone fruit. For example, insectaries share fruit growers’ focus on uniformity. Mixed maturities are disastrous, leading to some larvae pupating while others are too small to harvest.

Crop load management likewise matters. “The higher your densities, the more insects you’ll harvest, but the smaller the individuals will be,” says Pieterse.

By manipulating stocking densities, commercial insectaries can churn out high volumes of lower-quality larvae (for example, if breaking down food waste is the primary aim) or low numbers of high-quality larvae (for example, for generating broodstock). Most mass-rearing facilities aim to strike a balance between yields, size, and quality, as their larvae will be processed.

Whether producing a few thousand insects for research or mass rearing millions for sterile insect release or as a crop, Pieterse thinks entomologists and animal scientists have a lot to learn from each other.

“The mass production of insects is now where the poultry industry was 40 years ago,” she comments. “We have the technology to farm insects like we do chickens, but not many people understand how to optimise their production.”

According to Stenekamp, she still finds insects rewarding after more than a decade of working with them. “Like anything, it gets easier with experience, although every species is different,” she says. “But all insects have one big advantage: they don’t talk back.”