Parasite Wasps More Numerous than Once Thought

The large number of species of wasp that lays its eggs under the skin of unwitting caterpillars is even more diverse than previously thought according to researchers.

The wasps were reared from caterpillars collected in Area de Conservación Guanacaste (ACG), a biological reserve in northwestern Costa Rica.

By combining ecological and genetic data using a technique called DNA barcoding with the painstaking detective work of taxonomy, the researchers have dramatically increased – nearly doubling – the estimated number of species of parasitoid wasps. "This represents microgastrine wasps reared from approximately 3,500 caterpillar species in ACG," said Josephine Rodriguez, a doctoral student and microgastrine expert. "Since there are an estimated 10,000 species of caterpillars there, including many unsampled ones that mine inside leaves or live in fungi, this is just the tip of the microgastrine iceberg."

The wasps are extraordinarily specific to the caterpillar hosts they attack. More than 90 percent of the wasp species were found to target only one or a very few species of caterpillar, out of more than 3,500 caterpillar species sampled in ACG.

"One of the messages of this paper is that you really need all of these different kinds of data in order to tell the species apart – that just using the morphology alone, or the genetic data or the ecological information alone isn’t enough," said University of Illinois entomology professor James Whitfield, who led the taxonomic study. "However, once the species are distinguished, anyone can use the DNA barcode to rapidly and accurately identify one of them."

"The family Braconidae, to which the microgastrines belong, has about 15,000 described species in the world, and it’s been estimated to have 50 to 60,000 species, about the same as all vertebrates – all fish, mammals, amphibians, reptiles, birds – which is a lot!" Whitfield said. "And what we’re saying is that if anything we’re underestimating how many more there are."

-- Justin Jernigan

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