Emma E. Mackay

COEXISTENCE AND COMPETITIVE DISPLACEMENT INVOLVING TWO NATIVE ANT SPECIES (HYMENOPTERA: FORMICIDAE)

The invasion of Camponotus laevigatus (F. Smith) nests by Formica haemorrhoida- lis Emery is described. The C. laevigatus workers attempt to defend their nest from attack but retreat into the inner galleries of the nest where they are slowly eliminated by. the F. haemorrhoi- dalis wolkers. Although the invasion of C. laevigatus nests by F. haemorrhoidalis is a common occurrence, the two species coexist. This coexistence may be due to several factors: 1) Camponotus laevigatus is able to disperse greater distances than F. haemorrhoidalis and is therefore able to invade and establish itself in recently disturbed areas several years before the area is invaded by F. haemorrhoidalis. 2) Camponotus laevigatus is able to occupy habitats such as dense woods where F. haemorrhoidalis does not occur. 3) Coexistence may be temporary and C. laevigatus may ulti- mately be excluded from certain areas. The effect of F. haemorrhoidalis on the C. laevigatus pop- ulation may not be important; evidence indicates that a C. laevigatus population can inciease in an area heavily colonized by F. haemorrhoidalis. It is often assumed that competitive displace- ment involving native species is rare as an equilibrium between the species has been established in the past. The investigations of Brian, Pontin, Scherba, and that reported here show that dis- placement involving native ant species may be common, at least in disturbed ol artificial

Lasius xerophilus (Hymenoptera: Formicidae), a new ant species from White Sands National Monument, New Mexico

We describe a new species of the ant genus Lasius collected from the arid Chihuahuan Desert, a very unusual habitat for the genus. The workers, females and males of this species are similar to those of L. neoniger , but have more abundant erect hairs on the tibiae.