Pirate Bug Tag-Team Spells Double Trouble for Thrips

The minute pirate bug, Orius insidiosus, was formerly thought to work alone, spearing its prey with a long, needlelike beak and sucking out its victim’s juices. But now it appears this tiny agricultural ally of commercial growers and home gardeners may have a partner: O. pumilio, a closely related species found hunting with it on an organic farm in Alachua County in north- central Florida.

The 2008 discovery by Agricultural Research Service (ARS) scientists, reported in the June issue of Florida Entomologist, marks the first time the two pirate bug species have been observed prowling the same “hunting grounds”—the flowers of a crop of false Queen Anne’s lace—and stalking the same prey: Frankliniella bispinosa (Morgan), also known as Florida flower thrips.

Although O. insidiosus occurs throughout the United States and is used commercially to biologically control myriad crop pests, O. pumilio is a little-known species whose U.S. range until now had only been documented in south Florida, notes Jeff Shapiro. He’s an entomologist with the ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Fla.

Specimens collected from the Alachua County organic farm showed that O. insidiosus outnumbered O. pumilio by more than three to one. And yet both species preyed on thrips without apparent rivalry. Was this a case of insect magnanimity on O. insidiosus' part? No, the more likely reason was the abundance of thrips on the flowers, reports Shapiro.

Along with ARS colleagues and the organic farmer, Shapiro also observed that O. insidiosus males outnumbered females almost three to one—though for reasons yet unknown—while O. pumilio’s sex ratio was even. Additional collections and field surveys are under way to track other cases of coexistence and learn more about O. pumilio and its distribution. Ultimately, such information could yield new conservation strategies for bolstering the bugs’ numbers or improving their effectiveness as commercial biocontrol agents.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture.