Braconid Wasps Pupating and Emerging
Tobacco Hornworms, Manduca sexta (often found feeding on tomato plants and confused with Tomato Hornworms, Manduca quinquemaculata) are often the target of a species of a Braconid wasp (Cotesia congregata) that parasitizes beetle, moth, fly and sawfly larvae. The adult wasp lays her eggs inside the hornworm with her long ovipositor. The eggs hatch and the wasp larvae feed on the caterpillar. Eventually the wasp larvae emerge and spin silk pupa cases (cocoons) on the skin of the dying hornworm caterpillar, inside of which they transform into winged adults within four to eight days. Braconid wasps are extremely good at locating hornworms, even when there are very few to find. Because they parasitize hornworm, cabbage worm, aphid and gypsy moth larvae, Braconid wasps are considered important biological control agents. If you want to discourage Tobacco Hornworms in your tomato patch, allow the wasps to complete their metamorphosis – this accomplishes both the demise of the hornworm, as well as an increased population of Braconid wasps. (Thanks to Emily and Joe Silver for photo op.)
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Green Lacewing Larvae Use Corpses as Camouflage
Green lacewings are aptly named for the prominent venation of the adults’ wings. Some species in this insect family even have “ears” in the larger veins that allow them to detect the ultrasonic sounds made by hunting bats. Lacewing larvae and adults are both predators of soft-bodied insects such as aphids. Larval lacewings have long, hollow mandibles with which they puncture prey and suck out the liquefied contents, leaving the woolly husks. Some species of lacewing larvae have hairy backs, and camouflage themselves when in the presence of woolly aphids by sticking aphid husks on these hairs. These “trash packets” camouflage the lacewing larvae from predators, including ants that would otherwise attack the larvae if they recognized that they were lacewings and not woolly aphids.
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Ant Farmers
Certain species of ants have what is called a mutualistic relationship with aphids – a win-win situation for both the ants and the aphids. The ants protect the aphids from predators. In return, the aphids secrete droplets of “honeydew” from their abdomen when stroked by the ants’ antennae, which the ants devour. The act of stroking the aphids is referred to as “milking” them; hence, the ants are referred to as “farmers.”
Ants Farming Aphids
Some species of ants “farm” aphids. Ants and aphids have a mutualistic relationship, in which each benefits from the presence of the other. The aphids feed off of the sap of plants, which is low in nutrients. They must therefore consume a lot of sap in order to get adequate nutrition. As a result, the aphids excrete large quantities of waste, called honeydew, which is high in sugar content. This is where the ants come in – they love honeydew, and have actually learned to “milk” aphids by stroking them with their antennae, which stimulates the aphids to release honeydew. In return for this delicacy, the ants protect the aphids from predators. Chemicals on the ants’ feet tranquilize and subdue the aphids, and even inhibit their wing development, keeping them close by as a ready source of food. Ants have also been observed tearing the wings from aphids before they can become airborne.
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