Breaking the vicious circle

Though whiteflies have become a serious pest in south Florida, they are not without natural enemies.  Many species of parasites, parasitoids, and predators are important in controlling whitefly populations.  In our garden, the most visible threat to whiteflies is from one group of these predators: the lacewings.

An adult green lacewing (Chrysopidae) on a leaf with whiteflies.

An adult brown lacewing (Hemerobiidae) on a papaya leaf.

Lacewings were among the insects that I found most frequently in the garden, especially at night.  I would usually find one or two flying about and many more on the undersides of leaves colonized by whiteflies.  Even so, I was surprised one night to be able to see seven adult green lacewings from one spot -- each one on its own whitefly-covered leaflet of a Schefflera tree.  They did not seem to be actively eating the whiteflies; they may instead have been scouting for places to lay their eggs.

A row of lacewing eggs.

In some lacewing species, both the adults and the larvae will eat whiteflies and other small pests.  In other species, it is only the larvae that are important predators.  Although I did not see any lacewing larvae eating the plentiful whiteflies, I did find several green lacewing larvae roaming the garden in disguise.  Furthermore, from their disguises, I could tell that the larvae had not been restricting their diets to whiteflies.  For example, the larva pictured below seems to have had a large appetite for ants.

A green lacewing larva carrying a disguise of ant bodies.

A vicious circle

The mysterious cocoon was not the only odd-looking thing underneath the leaves in the garden.  Many of the leaves were marked with white, waxy spirals.

Eggs of a whitefly (Aleurodicus sp.) on the underside of a palm leaf.

These patterns were made by whiteflies (which are related to aphids and scale insects, not flies).  In some whitefly species, the adult females lay their eggs in spirals and cover them with a trail of wax.

An adult whitefly (Aleurodicus sp.) and eggs on the underside of a papapya leaf.

Although the adult whiteflies look harmless and the egg spirals could even be considered decorative, whitefly larvae are serious pests.  In addition to feeding on plant sap, they can transmit plant viruses when they pierce the leaves and the honeydew that they excrete can facilitate the growth of sooty mold.

A closeup of an adult whitefly on a palm leaf.