Last week we met stealthy debris carrying lacewing larvae. These masters of disguise search the bark of trees for soft bodied insects and mites in a season when most insects in the mid-Atlantic region are tucked away for a long winter’s nap. This week we meet another hibernal predator, the dusty-wing, kin of the lacewing and tiny hunter of spider mites, scale insects, whiteflies, and other very small soft bodied arthropods. Each winter during the January chill, the University of Maryland conducts a workshop aimed at teaching professional arborists and green industry professional strategies for managing landscape pests in sustainable ways. While examining a boxwood leaf through a microscope, one of the workshop students discovered something “wicked cool” cruising across a leaf. This tiny hunter is called a dusty-wing. With the visage of a chubby alligator, the dusty-wing larva measured less than 5 mm, just slightly larger than its spider mites prey.
Even in the depths of winter, on a warmish day dusty-wing larvae will search for tasty morsels of arthropod meat.
Dusty-wing larvae roam the undersides of leaves, bark of trees, and fruit searching for free range arthropod meat. Once discovered by the dusty-wing larvae, hapless victims receive a perfidious kiss and their body fluids are removed via short sucking tubes forming the mouthparts of the dusty-wing. After dining on many small prey and completing development, dusty-wing larvae spin silken cocoons on the undersurface of leaves or on other plant parts. The larvae possess specialized silk glands within their abdomens which exude silk from the anus. Like a weaver with a shuttle, a larva moves the tip of its abdomen to and fro in a circular dance to form the gossamer case in which it will turn into a pupa. This spinning ballet takes several hours to complete. After a week or so the adult dusty-wing emerges from the pupa and begins its quest for food and a mate.
Around and around the larva goes, exuding silk from the rear end to build a silken pupal chamber. Watch the tip of the abdomen move back and forth attaching strands of silk.
As the name implies, adult dusty-wings are covered with a fine layer of white wax. Specialized glands lining the abdomen of the adult dusty-wing produce ribbons of wax that the insect spreads across the surface of its body, legs, and wings to form a luxurious white coat. Undoubtedly, the waxy white coat aids in water retention for these tiny insects. In previous studies conducted we found dusty-wings to be common predators of nasty spider mites that attack boxwoods. Dusty-wings are believed to put a significant beat down on important pests of citrus including spider mites, scales, and whiteflies in Florida and California. The presence of these tiny hunters active in the thick of winter seems bizarre to me. Nonetheless their industrious pursuit of pests despite the cold is a welcome sight and a certain promise of warmer days to come.
We thank the hearty students of the 2017 Advanced Landscape IPM Short Course for providing inspiration for this episode. Two fascinating articles, “Characterization of the cuticular surface wax pores and the waxy particles of the dustywing, Semidalis flinti (Neuroptera: Coniopterygidae)” by Dennis R. Nelson, Thomas P. Freeman, James S. Buckner, Kim A. Hoelmer, Charles G. Jackson, and James R. Hagler, and “Biological notes on Coniopteryx vivina (Neuroptera: Coniopterigidae)” by Martin H. Muma were used to prepare this story.