Formica knighti

Formica knighti is often found in sandy soils nesting under low bushes. It is an uncommonly collected ant, there are numerous workers in mature colonies.

Identification
The head, mesosoma, and legs of this species are red or dark red, the gaster is black or dark reddish black. The dorsum of the head has a number of erect hairs, as does the ventral surface, the dorsum of the mesosoma, the outline of the petiole, and the gaster, the hairs on the scape are mostly appressed or only slightly raised from the surface. The posterior tibiae have erect hairs along the flexor surface, and few hairs are raised above the surface on the extensor surface. Many of the hairs, especially those on the mesosoma, are blunt-tipped, or weakly spatulate.

The queen is relatively large, bigger than the major worker. It is yellowish brown, with a medium brown gaster. The hairs are similar to those of the major worker, with the few hairs on the scape raised from the surface. The hairs on the mesosoma are blunt-tipped any nearly spatulate. Several hairs on the extensor surface of the tibiae are raised above the surface.

The species can be separated from most of the others in the microgyna group, as there are always a few hairs elevated above the surface of the tibiae on both the middle and posterior tibiae. It can be separated from similar species that also have such hairs on the tibiae, as the dorsum of gaster is dull and punctate and has few scattered, semierect hairs on the surface. It can be separated from Formica nepticula in which the gaster is moderately shining (although it is also punctate), by the densely punctate, dull surface of the gaster.

Buren (1944): This species has about the same coloration as Formica postoculata but does not seem closely related to it. F. postoculata has no hairs on the eyes, and no pilosity on the scapes or tibiae. It is much smaller in size, and there are several other differences in pilosity and in the shape of the head and thorax. F. knighti appears most closely related to Formica impexa, which it strongly resembles in the number and arrangement of the hairs. F. knighti may be distinguished immediately from impexa by the color of the head and thorax, which is deep red in impexa and scarcely infuscated except in the smaller workers. The head of impexa is less robust, more slender, and narrower in front; the clypeus is less produced and is rounded in front; the thorax appears less robust, and the mesoepinotal  constric­tion  is  shallow  and  narrow;  the  petiole is blunter and more rounded when  seen from behind; the erect hairs  are blunt or clavate, and the hairs on the scapes and legs are blunter  and erect. The erect hairs on the gaster are more numerous and larger and more conspicuous in impexa. The pubescent hairs also seem a little denser but shorter on impexa. The eyes of impexa are not distinctly hairy as in the new species. F. knighti, inci­dentally, is one of the few microgynous species with hairy eyes. Since the queen is unknown, there is no actual evidence that knighti is a microgynous species, but its general habitus and close resemblance to impexa lead the writer to believe so. It is certainly distinct from any species in the rufa group known to the author. F. knighti would perhaps key down to Formica oreas Wheeler in Wheeler's key to the Formica (1913), but workers of oreas may be distinguished immediately by the extremely abundant, very fine white hairs covering all parts. Many other differences show that areas is not closely related to knighti.

Distribution
Described from Bonaparte, Iowa. Also found in Massachusetts and New York.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.



Biology
Formica knighti is probably a temporary social parasite of Formica subsericea.

The type nest was located in pasture land covered with a rather dense growth of scrub oaks. The nest was well hidden under low bushes, and considerable plant debris had been used in the construc­tion of a low dome, immediately under which were numerous workers and the brood. (Buren 1942)

Nomenclature

 *  knighti. Formica (Formica) knighti Buren, 1944a: 303 (w.) U.S.A.

Worker
Length of  major  worker,  7.5  mm.

Head, excluding mandibles, about as broad as long, with posterior border feebly excised in the middle, the posterior corners rounded,  and sides slightly convex; scarcely narrower in front than behind. Mandibles 8-toothed. Clypeus rather angularly produced. Frontal area small, much wider than high. Frontal carinae evenly diverging, their length equal to twice the diameter of the antenna} foramina. Eyes hairy. First funicular joint one-fourth again as long as the second, the second slightly longer than the third, and each joint to the penultimate in turn slightly longer than the succeeding, the second almost one-half again as long as the penultimate. Promesonotal outline strongly convex. Mesoepinotal im­ pression deep and wide in large workers; marked by sutures before and behind. Declivity of epinotum a little longer than the base, meeting the latter with an angle of approximately 120-130 degrees. Petiole cuneate in profile, anterior and posterior  faces weakly convex. Superior border rather sharp; seen from behind angularly produced upward but usually notched at the tip. All surfaces opaque except the frontal area, which is smooth and shining, and  the  mandibles,  which  are moderately  shining  and  longi­tudinally striate. Erect hairs numerous, short, bristle-like, yellow, usually pointed at the tip but on the thoracic dorsum and gaster sometimes blunt or slightly clavate. Hairs present on all regions, even a few on the cheeks; few, however, on the gula. The numerous hairs on the scapes and legs short and strongly oblique or subappressed. Pubescence dense in all regions.

Ground color of head and thorax yellowish red, but usually heavily infuscated with black, even in the largest workers. Smaller workers have the head and thorax nearly as black as the gaster.

Type Material
Described from numerous workers taken from a single nest near Bonaparte, (Iowa) July 13, 1941.

Etymology
I take great pleasure in dedicating this species to Dr. H. H. Knight, Professor of Entomology, Iowa State College.