Last month we learned how aphids can wind up with a hole in their rear end courtesy of tiny parasitic wasps that turned them into mummies. This week we see how aphids can meet another gruesome end in the jaws of aphid lions. With ample rainfall and favorable temperatures, the lush growth on trees and shrubs continues to generate healthy populations of aphids on many garden plants. A week or so ago, on a dynamite pollinator attractor called Silphium perfoliatum, a.k.a. cup plant, I noticed a fine crop of aphids happily sucking sap on the underside of leaves. The thought of giving these gals (many aphids at this time of year are a “ladies only” society due to parthenogenetic reproduction) a squirt of insecticidal soap to quell their numbers ran through my mind for a brief moment. Fortunately, upon closer inspection of the festivities I spotted a murderous contingent of Mother Nature’s hit squad nearby, brown lacewing larvae. Brown lacewings are close kin to debris carrying green lacewings we visited in a previous episode.
Green and brown lacewings go by the colorful common name of aphid lions. Here’s why. Adult lacewings are attracted to fragrant odors emanating from plants infested with aphids. As they feed on plant sap, aphids produce a waste product called honeydew. The honeydew is a sweet concoction of sugars, amino acids, and other compounds. As this sticky goo degrades, telltale odors waft from the plants. Female lacewings cruising the landscapes in search of food for themselves and their babes sense aphid-related odors. The scent is like the smell of burgers and fries to a fast food junkie and sends a signal to the mother lacewing that “dinner is served”. Upon arriving on a plant, if the proper cues are present, the female green lacewing touches her abdomen to the surface of a leaf and draws out a thin strand of protein. At the tip of this protein stalk, she deposits a single egg. Why she goes to this trouble is not entirely clear. Perhaps, by placing the egg on a stalk, hungry predators including other lacewing larvae are less likely to snack on the tasty egg. Brown lacewing mothers seem to eschew this behavior and deposit their eggs directly on the surface of the leaf. After hatching, the tiny larva shinnies down the stalk and begins its search for food. If mom was clever and placed the egg in the right spot, a smorgasbord of aphids awaits nearby.
Aphid lions to the rescue! Last week my cup plant was loaded with aphids. Brown lacewing larvae came to town and now it’s so long aphids. When aphids appear, before you spray take a moment to see if some of Mother Nature’s hit squad, like brown and green lacewing larvae, have arrived to help.
Aphid lions have powerful, sickle-shaped jaws that grasp their prey. Once attached to the aphid, a pump in the aphid lion’s head is activated and the liquid life is sucked from the hapless victim. Aphid lions are reported to devour 200 aphids per week and several hundred during the course of their development. After shedding its skin twice to grow, the aphid lion spins a white cocoon and attaches the cocoon to the plant. Within this silken orb the transformation from alligator-like larva to pupa to winged adult takes place. After a few weeks in the cocoon, the beautiful adult lacewing emerges. The adult green lacewing has fantastic green or golden eyes and dozens of veins running through its wings, hence the name lacewing. Adult lacewings eat nectar and pollen and honeydew produced by aphids and other sucking insects. In addition to feasting on aphids, voracious lacewing larvae eat a variety of prey including caterpillars, spider mites, lace bugs, beetle larvae, and eggs of many kinds of plant pests. They are highly beneficial. Aphid lions can be purchased commercially and released on plants to help reduce pest populations. These fierce predators have been used to reduce pests with some success in agricultural crops such as cotton and strawberries and to reduce mealybugs on houseplants indoors and lace bugs on azaleas in landscapes and nurseries. As I watched aphid lions devour aphids with remarkable gusto, I wondered what our world would be like if aphid lions were the size of the German Shepherd next door.
The interesting references “Handbook of Biological Control” by Thomas S. Bellows and T.W. Fisher, and “Biological control in specific crops: Woody Ornamentals” by Paula Shrewsbury and Michael Raupp, were used to prepare this episode.