You may remember the great outrage in 2012 over the Starbucks Strawberry Frappuccinos drinks– the red food coloring in these drinks came not from strawberries, but an interesting little cochineal scale insect, called Dactylopius coccus. Although outwardly these scale insects appear to be fluffy and white, this is only a combination of wax and silk that the scale insect extrudes about its body. The actual scale insect itself is soft and red. Here in Tucson Arizona, we are close to this insect’s native range, and can find it on pretty much any prickly pear cactus grown around town. In fact, my walk into work goes right by a heavily infested cactus
One day, I saw a beautiful parasitic wasp apparently laying eggs in a mass of cochineal scales
This is curious, because cochineal scales have potent chemical in their “insect blood” that deters ants and is thought to prevent insects from developing inside of them (Eisner et al. 1980). So far, no parasitic wasps that specialize on cochineal scales have been found, so what is this wasp doing?
After a bit research, I came up with two explanations: 1) No one has found this parasitic wasp before, or 2) the wasp was actually laying eggs in something underneath the mass of cochineal scales. To test which explanation was supported by the evidence, I returned to the prickly pear cactus, lifted up the mass of cochineal scales. And I found…
a caterpillar!!!!
Not many caterpillars eat cochineal scales and hide underneath their fluffy remains, so after doing some more research I was able to identify the insects and piece the story together. This caterpillar, Laetilia coccidivora, specializes on eating cochineal scales by sequestering the scales’ defensive chemicals. These chemicals, however, have not stopped our little parasitic wasp, Brachymeria conica, from laying eggs inside of this caterpillar. These eggs will eventually hatch, and the wasp larvae will eat the caterpillar from the inside out, pupate, and then emerge as adult wasps. For more about the cochineal scales and all things that eat them, check out some of the interesting references below!
Some classic studies on carminic acid, which is responsible for the cochineal scale’s red color:
Eisner, Thomas, et al. "Red cochineal dye (carminic acid): its role in nature." Science
208.4447 (1980): 1039-1042.
Eisner, T., et al. "Defensive use of an acquired substance (carminic acid) by predaceous
insect larvae." Experientia 50.6 (1994): 610-615.
For more on the cochineal scale predators their parasitoids, and their hyperparasitoids:
Gilreath, M. E., and J. W. Smith. "Natural enemies of Dactylopius confusus (Homoptera: Dactylopiidae): exclusion and subsequent impact on Opuntia (Cactaceae)." Environmental Entomology 17.4 (1988): 730-738.
Post written and unattributed pictures and videos taken by Corinne Stouthamer
Not many caterpillars eat cochineal scales and hide underneath their fluffy remains, so after doing some more research I was able to identify the insects and piece the story together. This caterpillar, Laetilia coccidivora, specializes on eating cochineal scales by sequestering the scales’ defensive chemicals. These chemicals, however, have not stopped our little parasitic wasp, Brachymeria conica, from laying eggs inside of this caterpillar. These eggs will eventually hatch, and the wasp larvae will eat the caterpillar from the inside out, pupate, and then emerge as adult wasps. For more about the cochineal scales and all things that eat them, check out some of the interesting references below!
Some classic studies on carminic acid, which is responsible for the cochineal scale’s red color:
Eisner, Thomas, et al. "Red cochineal dye (carminic acid): its role in nature." Science
208.4447 (1980): 1039-1042.
Eisner, T., et al. "Defensive use of an acquired substance (carminic acid) by predaceous
insect larvae." Experientia 50.6 (1994): 610-615.
For more on the cochineal scale predators their parasitoids, and their hyperparasitoids:
Gilreath, M. E., and J. W. Smith. "Natural enemies of Dactylopius confusus (Homoptera: Dactylopiidae): exclusion and subsequent impact on Opuntia (Cactaceae)." Environmental Entomology 17.4 (1988): 730-738.
Post written and unattributed pictures and videos taken by Corinne Stouthamer