Pheidole inquilina (Wheeler)

Wilson, E. O., 2003, Pheidole in the New World. A dominant, hyperdiverse ant genus., Cambridge, MA: Harvard University Press : 580

Pheidole inquilina (Wheeler)

Epipheidole inquilina Wheeler 1903h: 664. Combination m Pheidole by Cole 1965: 174.

Types Mus. Comp. Zool. Harvard.

etymology L inquilina , temporary guest, lodger.

diagnosis A permanent social parasite of Pheidole pilifera (including " subspecies coloradensis "). The queen is very small, and easily recognized by her subangulate occipital corners. Aside from these two traits, and possibly the rounded tips of the propodeal spines, inquilina queens are little modified in general from typical queens of other, non-parasitic species of Pheidole . Measurements (mm) Syntype queen: HW 0.70, HL 0.70, SL 0.64, EL 0.24, PW (not measured). Color Queen: light brown.

Range Colorado, Nebraska, and Nevada: rare (Wheeler 1910b; M. R. Smith 1940a; Gregg 1963; d. R. Smith 1979). In Colorado, inquilina occurs at about 2000 m.

biology In Colorado Pheidole inquilina was found by Wheeler with the host species P. pilifera (" subspecies coloradensis ") at about 2000 m, under rocks most likely in pinyon-cedar-oak woodland. The species is the least anatomically modified of the pheidoline social parasites. It is therefore not very surprising that both the major and minor workers have been discovered in addition to the usual queens and males. However, these castes are evidently in a state of evolutionary decline. In 19 infested nests of the host species excavated by A. C. Cole (1965), 8 contained a few individuals of inquilina ; and of these, one nest yielded only a single minor worker of inquilina , while another contained one minor and one major. M. R. Smith (1940a) noted the close resemblance of the worker castes between the two species, and suggested that inquilina was derived in evolution from pilifera or a related species. In other words, Emery's rule that social parasites are close relatives of their hosts is exemplified.

figure Syntype, queen. COLORADO: Broadmoor, Colorado Springs, 2000 m (William M. Wheeler). (Majors and minors have been discovered but are not figured; see under Biology below.) Scale bar = 1 mm.