beneficial insects in the landscape

About 120,000 different species of flies annoy folks around the world. They are found everywhere including the Antarctica. Sometimes it is hard to remember that flies are an integral part of our ecosystems.

Flies can be beneficial and necessary, aiding in controlling other insect pests, acting as pollinators, recyclers and scavengers, and they are also a part of the food chain. Remember only bees (and a few wasps) pollinate more plants than flies.

The multi-beneficial black soldier fly (Hermetia illucens) is probably the best-known member of the Stratiomyidae family in the Diptera order. Diptera is taken from the Greek “di,” which means two, and “ptera” meaning wings, as most flies only have two wings.

Aristotle used the term more than 2300 years ago. In the order, Diptera, the word “fly” is always separate from the rest of the common name. Insects of other fly orders are always written as one word, such as dragonflies and sawflies. But we digress. The black soldier fly is one of a group of true flies. They are found mostly in the tropical/subtropical Western Hemisphere and Australia, breeding in compost, manure and outdoor toilets.

Black soldier flies can be seen in bright, sunlit areas, resting on nearby structures or vegetation and frequenting flowers of the daisy and carrot families. They are one of the most beneficial flies in existence and are considered non-pests. The adult black soldier fly does not have mouthparts and does not feed upon waste. They do not bite, and as only the larva feed, are not associated with transmitting any diseases. Also, this species makes the breeding areas of houseflies less desirable.

The hale and hearty adults are about 7/8-inch long. Adult black soldier flies are weak fliers and will spend their time resting in and around animal production facilities. They are black with dusky wings held over their backs when reposing. The black soldier fly’s first abdominal segment has two clear areas near its second segment giving it a “wasp waist”.

Gender-wise, the female’s abdomen is reddish at the top and the male’s abdomen is rather bronze. Their upper legs are black with white-yellow tarsi or forelegs. Black soldier fly’s antennae are elongated, projecting forward from the head, which is tapered and does not have an arista (sensory organ of touch).

Adult black soldier flies might be mistaken for an organ pipe mud dauber wasp as both have long antennae, the same pale colored tarsi, and the two small transparent areas in the abdominal segments. Adults appear as early as April but many do not emerge until late summer. However, it is the black solider fly’s larva that is of most interest.

This species mates in flight and females deposit egg masses (about 500 eggs) near edges of decaying organic matter. Eggs incubate anywhere from four days to three weeks before hatching. The oval egg can be up to 0.039 inches in length. Initially the egg is a cream color but darkens over time. Once hatched, the larva is an off-white and about 0.07 inch long.

As it develops through six instars, it becomes a reddish-brown. Mature larva can be anywhere from 1/8 to over an inch in length and quite plump. Larvae have been described as “torpedo-shaped and slightly flattened” with an exoskeleton, or skin, that is firm, tough, and leathery, and its back has spiracles (breathing pores). The yellow to black head is tiny and narrow.

What is of interest is that larvae are being used in manure management. Not only does the black soldier fly larva do its duty in manure reduction, but carries through as a feed supplement, and battles bravely in the war of pest fly control. Best of all, this is all interwoven. Read on, as this is really cool stuff.

First off, manure management reduces environmental damage that can result from large accumulations of manure. Black soldier fly larvae are scavengers and thrive on many kinds of decomposing organic matter, including algae, carrion, compost heaps, manure, mold, plant refuse, and the waste products of beehives.

They have large and powerful chewing mouthparts allowing them to shred and devour waste. These gluttonous little creatures are able to digest organic compound before the compounds have time to decompose, thereby immediately eliminating odor. The black soldier fly larva’s digestive system leaves behind a fraction of the original weight and volume of waste.

Statistically, food waste in the United States, could be significantly reduced and waste reduction of farm animals (chickens and pigs) might even reach 75%. Simply put, manure is rapidly decomposed by the black soldier fly larvae, greatly reducing the amount and odor, along with any potential disease problems.

Secondly, this non-pest larvae converts the manure’s nutrients into 42% protein and 35% fat feedstuff. This conversion of waste into feedstuff is called bioconversion and, consequently, the larvae can be fed right back to the animals or birds that generated the waste or used as feed for fish or livestock. It can be ground up and fed to earthworms or red worms for a second round or just used as compost. The larva is dry, friable, and odorless.

In addition, many experts believe that the high calcium content of the larvae (also called “phoenix worms”) may halt or reverse the effects of metabolic bone disease. This biomass, of larvae harvested nutrients, is worth about the same as meat and bone or fishmeal. It can be easily and economically transported, unlike unprofitable manure, and reduces the need to import concentrates that are added to other types of feed.

Thirdly, the larva’s eating style discourages the development of pest flies. As large populations of black soldier fly larvae churn manure, they make it more liquid and less suitable for, not only egg-laying (oviposition) by the pest fly, but the actual development of the pest fly’s larvae, thus reducing them substantially.

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