This spring a large black locust tree was removed from my backyard. In a fit of revenge, the roots of the locust sent hundreds of shoots skyward turning the lawn into a miniature locust forest. The succulent new growth of these saplings provided the perfect food and shelter for aphids and an aphidtopia erupted on these shoots. As aphids feed on plant sap, they produce a waste product called honeydew. Honeydew is a sweet concoction of sugars, amino acids, and other compounds. As this sticky goo degrades, telltale odors emanate from the aphid-infested plant. A delicate insect with diaphanous wings called a lacewing, the adult stage of the aphid lion, is cruising the hood in search of food for herself and her babes. The aphid-related odors wafting from my locust tree are like the smell of burgers and fries to a fast food junkie. They signal the mother lacewing that "dinner is served." Upon arriving on a plant, if the proper cues are present, the female lacewing touches her abdomen to the surface of the leaf and draws out a thin strand of protein.
Lacewing eggs are placed on stalks above the leaf surface.
At the tip of this 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 aphid lions, are less likely to snack on the tasty egg. After hatching, the tiny aphid lion shinnies down the stalk and begins its search for food. If mom was clever, a smorgasbord of aphids may await nearby. The aphid lion is a close relative of the antlion we met in Bug of the Week on June 20 - Lions in the sand. Like its cousin the antlion, aphid lions have powerful, sickle-shape jaws that grasp the prey. Once attached to the aphid, a pump in the aphid lion's head sucks the life 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 it 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 lacewing adult emerges. The adult green lacewing has fantastic golden eyes and dozens of veins running through its translucent wings. Lacewings adults eat nectar and pollen and honeydew produced by aphids and other sucking insects. Lacewing larvae are voracious and eat a variety of prey in addition to aphids including caterpillars, spider mites, beetle larvae, and eggs of many kinds of plant pests.
The aphid lion spins a cocoon and pupates within.
The aphid lion clasps a hapless aphid and sucks its blood.
Aphid lions can be purchased commercially and released on plants to help reduce pest populations. Aphid lions have been used to reduce pests with some success in agricultural crops such as cotton and strawberries, and to reduce mealybugs on houseplants indoors as well as sap-sucking bugs in landscapes and nurseries. As I watched the aphid lion devour an aphid with remarkable gusto, I couldn't help but be thankful that aphid lions are not the size of the German Shepherd next door. If they were, we would all be running for our lives!
References
To learn more about the fascinating lives of aphid lions and lacewings, visit the following web sites:
http://www.entomology.wisc.edu/mbcn/kyf103.html
http://www.inhs.uiuc.edu/cee/biocontrol/predators/habitat.html
http://www.nysaes.cornell.edu/ent/biocontrol/predators/chrysoperla.html