Have you seen this cottony-looking mass on papaya trees in the landscape? This mass is composed of the cocoons of braconid wasp larvae that emerged from one of the large sphinx moth caterpillars (hornworms) that feed on papaya. Hornworms can be very damaging to papaya, so it’s a great sign when we see signs of this wasp. Most likely, the hormworm that was attacked in this case is the juvenile ello sphinx moth, Erinnyis ello.
A few weeks ago I wrote about another beneficial Braconid wasp that attacks the tomato hornworm. The lifecycle and mechanism of control for this one is similar. The wasp lays its eggs just under the skin of the hormworm. When larvae emerge from the eggs, they begin feeding on the insides of the still-living hormworm. When the juvenile wasps have matured, they eat through the skin of the hornworm, and spin their cocoons, after which the hornworm will die. Adult braconid wasps will then seek out other hormworms to attack. The difference between this braconid wasp and some others is that the host hornworm is gone here, whereas in other cases we find it still intact.
The Braconid family is made up of over 1000 species of tiny wasps that pose no threat to humans. Insects in this family act as parasitoids to control pest insects, including a number of harmful caterpillars, aphids, and other landscape pests. These beneficial insects are another good reason to use pesticides responsibly in the landscape and to spot-treat when possible.