Hydrocarbon-released nestmate aggression in the Argentine ant, Linepithemahumile, following encounters with insect prey

Argentine ants, Linepithema humile, were attacked by their nestmates follow ing contact with a particular prey item, the brown-banded cockroach, Supell a longipalpa. Contact with prey, as brief as 2 min, provoked nestmate aggre ssion. Argentine ants contaminated with hydrocarbons extracted from S. long ipalpa also released nestmate aggression behavior similar to that released by the whole prey item, confirming the involvement of hydrocarbons. In cont rast to S. longipalpa, little or no nestmate aggression was induced by othe r ant prep from diverse taxa. A comparison of prey hydrocarbon profiles rev ealed that all hydrocarbons of S. longipalpa were very long chain component s with 33 or more carbons, while other prey had either less, or none, of th e very long chain hydrocarbons of 33 carbons or greater. We identified the hydrocarbons of S. longipalpa and some new groups of long chain hydrocarbon s of L. humile. The majority of S. longipalpa hydrocarbons were 35 and 37 c arbons in length with one to three methyl branches, and closely resembled t wo previously unidentified groups of compounds from L. humile of similar ch ain length. The hydrocarbons of S. longipalpa and L. humile were compared a nd their role in the Argentine ant nestmate recognition is discussed. (C) 2 001 Elsevier Science Inc. All rights reserved.