Trash Bug Versus Mealybug: Unique Insect Interaction Filmed for First Time  

By Erin Powell, Ph.D.

As an entomologist with the Florida Department of Consumer Services, Division of Plant Industry, I receive shipments of plant material from all over the world. Any day may come with a surprise: a new pest species established in the state, an intercepted exotic species coming from overseas, or perhaps a species unknown to science. Each year I provide over a thousand identifications of scale insects, mealybugs, and whiteflies to make regulatory decisions that protect Florida’s agriculture and our native ecosystems.

A sample I was sent in late 2022 turned out to be particularly exciting. A plastic bag filled with sugar apple (Annona sp.) leaves was delivered from South Florida, from inspectors looking for an identification of the mealybug pests. There, amid a teeming infestation of coconut mealybugs (Nipaecoccus nipae), was a “trash bug” busily piling wax onto its back, seemingly unbothered by being shipped across the state and now observed under bright artificial lights.

“Trash bug” is a colloquial name often used for green lacewing larvae (Neuroptera: Chrysopidae). You may have seen them bumbling around the garden like a walking piece of lint. The nickname refers to the behavior of many lacewing larvae that adorn themselves with assorted natural materials: lichen, plant trichomes, tiny bits of wood, prey remains, even spider silk.

These ubiquitous predators are important biological control agents, known for their voracity toward common plant pests such as mealybugs, aphids, mites, and thrips. But, up to now, lacewings have only been documented using the wax of a few species of scale insects, aphids, and flatid nymphs to construct their dorsal packets. Many of these kinds of insects produce honeydew and are tended by ants, which means camouflaging as the prey is critical to avoid being detected. Therein lies the comparison to the classic idiom “wolf in sheep’s clothing” made by previous researchers of lacewings. The predator must blend in as a sheep if they are to deceive the shepherd.

I quickly grabbed my camera, equipped with the Canon 65-millimeter MP-E macro lens that I use extensively to document arthropods both in the field and laboratory. Using its mandibles, the Ceraeochrysa claveri lacewing larva scooped wax up from the plant material with which it was shipped and flipped its head backwards to drop the wax onto its back, making a packet held in place by tufts of long hairs. What was particularly interesting was the incorporation of live mealybug nymphs into the packet, perhaps unavoidable given how many of them were densely packed amid the sample. When they do this in the wild, I wondered, could the lacewings potentially transport mealybug nymphs to new areas?

The lacewing larva alternated between constructing its dorsal packet and eating mealybug nymphs and adults, draining a first-instar mealybug nymph in less than 45 seconds with its menacing sucking mouthparts. The quick and efficient feeding puts their value as a biological control agent on display.

But there’s another layer to this story, which I shared in an article published in December in the open-access journal Insecta Mundi. Mealybugs may rely on ants as bodyguards, but they themselves are not defenseless. On the back of most mealybug species are two pairs of slit-like openings called ostioles. When disturbed or threatened, a bubble of liquid body contents, containing free wax, exudes from the ostiole(s). This “reflex bleeding” and the rapid drying of the fluid can cause the mouthparts of their predators to be totally gummed up, even leading to death in early-instar lacewing larvae that have the misfortune of contacting the fluid.

In the videos I captured, the lacewing larva had a strong distressed reaction, quickly retreating to wipe its mouthparts on the leaf. But, despite it getting itself into a sticky situation, I was able to rear this larva successfully to adulthood.

Long interested in anti-predator defenses, my expertise mainly lies in arachnids and scale insects. I knew little about lacewings until stumbling upon this chance discovery. They are so common and charismatic, I thought surely more videos are out there of this entertaining behavior. But, as I researched further, that was not the case. The footage in this study also represents the first video documentation of reflex bleeding by mealybugs to my knowledge, which is also poorly studied despite the importance of mealybugs as plant pests. Reflex bleeding probably has implications for the success of biological control agents on mealybugs, and more work is required to further understand both the efficacy and the chemical components of the ostiolar fluid.

So, next time you see a bumbling ball of lint, take a closer look. What is the lacewing larva’s packet made up of? Can you catch them in the act of constructing it?

Erin C. Powell, Ph.D., is a research scientist and curator at the Florida State Collection of Arthropods within the Florida Department of Agriculture and Consumer Services, Division of Plant Industry. See more of Erin’s photography and research on X/Twitter and Bluesky. Email: erin.powell@fdacs.gov.