The word “insect” equals “pest” in a lot of people’s minds, especially in agriculture. But we have to remember that the insects that attack crops actually represent a small number of all insect species. In fact, a few are here to help us against their annoying cousins. So this week, I want to highlight some insects that are more friend than foe.
- Lacewing and lady beetle larvae
Some of these beneficial insects are natural born killers. I know that sounds ominous, but believe me when I say that that’s a good thing. Being a voracious predator at birth means no time is wasted growing up before being a productive member of society. Two good examples are the larvae of lady beetles and lacewings, which are driven by a hunger for their fellow insects from the moment they hatch. Both larvae are slender, cigar-shaped critters and can be confused for each other by the unwary. To tell them apart, look for the mouthparts. Lacewings (aka “aphid lions”) have large, wicked-looking mandibles, good for seizing prey. The mouthparts of lady beetle larvae are reduced in comparison. Lacewing larvae are dull in color compared to lady beetles, which tend to be black with orange or yellow markings, but they do like to dress up. Like a tiny, insectoid Buffalo Bill, some species of lacewings wear a gilli suit made from past victims. This allegedly allows them to blend in amongst their prey like the proverbial wolf in sheep’s clothing.
- Robber flies
A lot of the time, insect names can be pretty boring. They don’t tell you anything about the insect or why should you care. But in a few special cases, the name tells you everything you need to know. Like a thief, the robber fly steals, but what it snatches isn’t gold and jewelry, but lives. Robber flies are mostly slender insects, built for speed and bringing a voracious appetite to the table. They are generalist predators that scan the area from a well-chosen perch and bursting forth when a potential meal flies by. The robber fly will snatch their prey in mid-flight and immediately inject the victim with a neurotoxin into their soft tissue. Once pacified, the robber fly returns to its perch to enjoy a hand-made milkshake.
- Insidious flower bug
The insidious flower bug’s name also demands attention. The name may sound evil, but these tiny bugs are some of the good guys. At less than 1/8 inch long, you wouldn’t expect these critters to be effective predators… and you would be wrong. Insidious flower bugs are well-adpated for attacking some of the smallest prey, keeping populations in check before we humans can even detect a problem. Thrips, aphids, and the eggs of other insects fall before the piercing bites of the bug’s syringe-like beak. Make sure you show these guys some respect if you see them in the field. If not, you might receive an over-sized bite in return.Not every insect can be the predator we want, however. Some… some just are the predators we need. You see, not all insects like to play fair in the game of life. When the robber fly chases down prey, there’s a sportsman-like feel to the hunt; like there’s something fair about the experience.
The next two groups I’m going to talk about don’t have time for any of that.
- Tachinid flies
Tachinid flies are a family of mostly drab flies that can easily be mistaken for smaller house flies. Some can be metallic colors as well, but for the most part they are pretty unassuming. That is… until it’s time to make the next generation.You see, many tachinid flies are what we call parasitoids. A parasitoid is any organism that requires part, but not all, of its lifecycle feeding off a living host. These flies prey on the caterpillars of butterflies and mosts, especially pests like armyworm and european corn borer. Laying their eggs on the unsuspecting larvae, the fly maggots later hatch and burrow inside to feed on the still living caterpillar. Once mature, they reenact that chest burster scene. Despite the squeemish results, tachinid flies can easily reduce pest pressure in an area by 50-70%.
- Trichogramma wasps
Our last friendly group of insects are also parasitoids, though thankfully they tone down the ick factor a bit. Species in the genus Trichogramma are egg parasites and were first identified by entomologist and biological control proponent, Charles Valentine Riley. Since their discovery, Trichogramma wasps have become one of the most widely-released insects for biological control. These wasps are small- usually less than 1 mm in length- and you may at first mistake them for a fruit fly, given their often tan color and bright red eyes. But the slender waist and stinger at the end should make it clear that these ladies are all wasp.They inject their eggs into those of larger insect, where the larvae quickly hatch and feed on the unfortunate victim. Their growth is rapid and new adults can emerge as soon as eight days later. Because they are generalists, Trichogramma wasps can suppress a number of pest species in the same area, making them a boon for biocontrol efforts.
The services beneficial insects provide is hard to quantify and we’re still trying to get an accurate picture of how much they impact agricultural pest management. But it’s indisputable that they are there to help.