Researchers discover new species of gall wasp

Discovery adds new species to Rice lab’s ghoulish insect menagerie
More than 50 species of wasps in genus Allorhogas live in Central America, but only two species had been documented in the United States prior to the discovery of four new species described this month in a study by biologists from Rice University and the National Autonomous University of Mexico. The new species (left to right) are: Allorhogas belonocnema, discovered in McAllen, Texas; Allorhogas gallifolia, discovered at Rice University in Houston; Allorhogas bassettia, discovered in the Florida panhandle; and Allorhogas caulinarius, discovered at several locations in Florida. Credit: Egan lab/Rice University

A horrifying insect soap opera with vampires, mummies and infant-eating parasites is playing out on the stems and leaves of live oak trees every day, and evolutionary biologist Scott Egan found the latest character—a new wasp species that may be a parasite of a parasite—within walking distance of his Rice University lab.


Egan, an associate professor of biosciences at Rice, studies gall wasps, tiny insects that cast a biochemical spell on live oaks. When gall wasps lay their eggs on oak leaves or stems, they chemically program the tree to unwittingly produce a tumor-like growth, or gall, which first shelters the egg and then feeds the larval wasp that hatches from it.

Egan describes the wasps as “ecosystem engineers,” because their galls are attractive morsels that harbor a supporting cast of opportunistic ne’er-do-wells, thieves and killers. It’s a great setting to study how competition for resources drives evolution, and Egan and his students have spent more than a decade documenting the eerie, interspecies who’s-eating-who drama.

The latest species they discovered at Rice, Allorhogas gallifolia (al-UHROH’-guhs GAHL’-ihf-ohl-eeuh), is one of four new wasp species from the genus Allorhogas that Egan and collaborators Ernesto Samacá-Sáenz and Alejandro Zaldívar-Riverón at the National Autonomous University of Mexico (UNAM) in Mexico City described in a study this month in Insect Systematics and Diversity.

“They lay their egg in another wasp’s gall,” Egan said of A. gallifolia, which his group first hatched in 2014. “They’re using the gall as a resource, and we’re still not certain how, but I think they’re attacking herbivorous caterpillars that are feeding on the gall tissue, and the wasp larva are eating those caterpillars after they hatch.”

He said more than 50 species of Allorhogas have been found in Central America and Mexico, but only two species were previously documented in the United States, one at the University of Maryland campus in 1912 and another some years later in Arizona.

Discovery adds new species to Rice lab’s ghoulish insect menagerie
Allorhogas gallifolia is a new species of wasp discovered in live oak trees at Rice University. First collected in 2014 by students in the lab of Rice evolutionary biologist Scott Egan, A. gallifolia is one of four new wasp species described in a study this month by Egan and collaborators Ernesto Samacá-Sáenz and Alejandro Zaldívar-Riverón at the National Autonomous University of Mexico in Mexico City. Credit: Ernesto Samacá-Sáenz/UNAM

The A. gallifolia found at Rice was collected as part of an effort to describe the community of natural enemies for one

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