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Maximizing Mealworms: Research Aims to Improve Rearing Methods

yellow mealworm - Tenebrio molitor - larva

Yellow mealworms (Tenebrio molitor) have been produced since the 1950s as fish bait, food for pet reptiles and amphibians, and to attract bluebirds to backyard feeders. But they are a growing source of protein for animal feed and for humans in an ever-hungry world. Researchers at the U.S. Department of Agriculture have been conducting long-term research on mass-rearing methods to improve the production of mealworms for food and feed. (Photo credit: Flickr/AJC1, CC BY-SA 2.0)

Ed Ricciuti

Ed Ricciuti

By Ed Ricciuti

Dubbed “The Mealie Master” by the outdoor media for pioneering development of techniques and tackle for hooking trout with mealworms, outdoor communicator and marketer Matthew Wettish of Killingworth, Connecticut, vouches that the sturdier the mealworm, the better the catch.

“Last thing I want to do is grab all my gear, drive an hour plus to the river and get there only to find dead mealies,” he says. As far as selecting mealworms, he says, “health and stamina are paramount.”

Figuring out how to raise a better mealworm on an industrial scale—not just for anglers but also, on a larger scale, as animal feed and even human food—is the subject of a research project, covering eight years, described in a new study published today in the open-access Journal of Insect Science. The article is part of a new Journal of Insect Science special collection on mass rearing of high-quality insects.

Mass Rearing of High-Quality Insects

Mass rearing of insects is critical for efforts such as biological control of pests or producing insects for food and feed. Check out the new special collection on Mass Rearing of High-Quality Insects, published in the open-access Journal of Insect Science.

The project’s findings bode well for the growing edible insect industry because it suggests the efficiency and cost effectiveness of producing mealworms can be improved by selective breeding. After eight years, mealworms produced in the study were three-quarters larger than the stock from which they originated.

Already a $55-million market, the industry banks on mealworms—larvae of darkling beetles—as a potential protein source for animal feed and, beyond that, for humans in an ever-hungry world. Before that happens, however, the cost of mass producing mealworms for human and animal food needs drastic cutting. As the research paper notes, “The methods for mass producing insect biomass remain primitive and inefficient, requiring high levels of manual labor.”

Seeking a way to turn out more product with less effort, a team of researchers led by Juan A. Morales-Ramos, Ph.D., of the United States Department of Agriculture’s National Biological Control Laboratory in Stoneville, Mississippi, has attempted to demonstrate experimentally that improving rearing conditions, focusing on selecting for larger pupae over an eight-year period, could produce a better yellow mealworm (Tenebrio molitor).

yellow mealworm - Tenebrio molitor - adult

Perhaps better known for its larval form, the yellow mealworm (Tenebrio molitor) is a beetle in the family Tenebrionidae, known as darkling beetles. (Photo credit: Pest and Diseases Image Library,

And it did, with a caveat. On one hand, the researchers found that over time they could select mealworms to develop a strain that, compared to the strain from which it emerged, grew faster and to a “significantly larger” pupal size, produced relatively more young, and used food more efficiently. On the other hand, though, the survival rate of the larvae dropped from that of the so-called “ancestral” strain. Therefore, the total biomass of mealworms produced evened out.

Matt Wettish

Yellow mealworms, larvae of the beetle Tenebrio molitor are an emerging protein source for animal feed and even food for humans, but they’ve long been popular as fish bait. Connecticut angler Matt Wettish uses mealworms almost exclusively and has been dubbed the “Mealie Master” in the fishing community. According to Wettish, the sturdier the mealworm, the better the catch. (Photo courtesy of Matt Wettish)

The project demanded excruciating attention to detail. Daily, for eight years, pupae were sorted, counted, and weighed. As selection progressed, pupal weights increased. The researchers also found that weight increased as the density of larvae in rearing containers decreased.

The scientists focused on pupal size because previous research has shown the biomass production can be optimized by selecting for that trait. At the same time, even though selecting for desirable traits is a key to bringing down costs of any agricultural production system—and insect farming is just that—it never has been used to produce yellow mealworms.

True, mealworms have been produced since the 1950s as fish bait, food for pet reptiles and amphibians, and to attract bluebirds to backyard feeders. But more effort has gone into keeping them from infesting human food, such as flour, than to using them as a source of food. And mealworms for people to eat are still mostly a novelty market.

Admittedly, it may take marketing skill to sell the idea of munching mealworms to the American public at large, but, worldwide, 2 billion people regularly eat insects of one type or another. Mealworms have many features that could make them stand out on the menu. Research suggests they are healthier than beef, chicken, and pork. Moreover, they are an environmentally sound product. Farming mealworms takes up much less space and uses less water than livestock and produces a much smaller amount of greenhouse gasses.

The next step in the on-going effort to improve mealworm farming is research to determine the relationship between pupal size and development time as well as how to select for higher survival in the bigger, better mealworms. Eventually, it could lead to people everywhere making a meal of mealworms.

Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.

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