Lasius coloradensis

This species nests under stones in rocky soils or sandy soils.

Identification
The workers of this species have a petiole with a relatively sharp apex (as seen from the side), which is usually concave or notched as seen from the front. The hairs on the underside of the head are usually 0.20 mm or less in length, and usually cover only the posterior 3/4 or 1/2 of the length, the hairs on the gaster are usually less than 0.22 mm in length, and are uniformly distributed across the surface. The side of the second tergum of the gaster has dilute to moderate, appressed pubescence, the pubescence on the remainder of the ant is usually only moderately abundant. (Mackay and Mackay 2002)

Distribution
Ranges from New Mexico, Colorado, and Utah north to Manitoba and west to Alberta and Oregon.

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



Habitat
Ranging from prairies and deciduous forests, ponderosa pine - Gamble oak transition, to coniferous forests. (Mackay and Mackay 2002)

Biology
Wing (1968) - Of the 70 samples received for study, 6 had associated data on nests; 1 colony was under cow dung, 4 were under stones. Sandy soil was indicated in 2 of the 6 samples. Most of the samples reported as Lasius claviger by Wheeler and Wheeler (1963) are coloradensis. The data of their paper suggest that many coloradensis nests are covered by stones. In the paper by Cole (1954), the colonies reported as coloradensis are Lasius latipes. One of those reported as latipes is coloradensis (N. Beaverhead). Two of those reported as claviger are coloradensis (Bandelier and Mescalero National Monuments). The 2 nests of coloradensis that could be associated with the data of this paper were under stones on dry grassy slopes under cover of scattered trees. Based on data associated with specimens and that in the literature references cited above, the altitudinal range of this species is from below 2000 to above 7000 feet.

Reproduction
Wing (1968) - Of the 13 dated samples containing alates, July 30 and September 16 are the extreme dates for those associated with workers. One sample collected on September 16 contained alate and dealate queens but no workers. Another collected on December 27 contained only dealate queens. Wheeler and Wheeler (1963) listed September 16 as the latest date for collecting winged males and females of claviger (= mostly  Lasius coloradensis). A comparison of the dates cited above with those given for claviger in the general section treating nuptial flights, indicates that the flights of coloradensis average much earlier than those of claviger.

Associations with other Organisms
Nest Guests - Schwartz (1895) reported that T. Ulke collected (Coleoptera: Pselaphidae) in the Black Hills of South Dakota. The host ant, listed as claviger, was probably Lasius coloradensis.

Nomenclature

 *  coloradensis. Lasius (Acanthomyops) interjectus subsp. coloradensis Wheeler, W.M. 1917a: 532 (w.q.m.) U.S.A. Combination in Acanthomyops: Creighton, 1950a: 429; in Lasius: Ward, 2005: 13. Subspecies of claviger: Creighton, 1950a: 429; Raised to species: Buren, 1950: 185. See also: Wing, 1968: 78.

Worker
Wing (1968) - Very closely similar to Lasius claviger, but averaging and ranging smaller. Standing body hairs more numerous and shorter; this difference between the two sibling species is especially evident on the dorsum of the gaster. Also the second and third femora frequently have at least a few suberect standing hairs. Pubescence more dilute and longer. Body color averaging darker, usually a yellowish brown to brown.

Queen
Wing (1968) - Quite similar to claviger, but SI at least 67, usually 70 or more. Antennal scapes and funiculi never more than slightly clavate. Somewhat more pilose and less pubescent. Body color darker, usually a very deep brown, often appearing nearly black to naked eye.

Male
Wing (1968) - Similar to claviger, but smaller; usually AL 1.50 mm or less, HW 0.99 mm or less, SL 0.62 mm or less, and terminal width of pygostyle 0.03 mm or less. Scale width at level of petiolar spiracles not over 1.3 times its height above spiracles. Pilosity moderate; pubescence dilute to very dilute. Body color dark brown, often appearing black or nearly black to naked eye.

Hybrids
Wing (1968) described a hybrid form of this species.

Lasius latipes × coloradensis hybrid
When the manuscript of the present revision was nearing completion, I noted that Weber (1935) had reported collecting alpha-latipes queens on September 2, 1931 from Towner, McHenry Co., North Dakota. In this paper on Formica obscuripes, he reported on their collection as follows: "Live workers, males and dealate alpha and beta females of Lasius latipes Walsh were found in digging up an obscuripes nest at a depth of about two feet (61 cm.). They did not seem to be captive and were possibly an independent colony." Upon my request, Dr. Weber sent me a beta queen and 3 "alpha" queens, 1 lacking a head. He was unable to locate the workers and males. The study of these specimens was of particular interest, because I knew of no other alpha queens collected so far outside the known range of claviger. Claviger and coloradensis are so closely related that the previous absence of records of latipes × coloradensis seemed odd, especially since latipes × claviger is our most frequently collected hybrid taxon.

A study of these specimens showed the beta female to be a perfectly typical latipes queen. The three "alpha" females resembled latipes × claviger queens closely enough to pass for small variants of this hybrid. Assignment of these queens to latipes × coloradensis was based both on structural characters, largely metric, and the known ranges of claviger and coloradensis.

Queen
Bears a close resemblance to latipes × claviger, from which it cannot readily be separated.

Ranging and averaging smaller for most metric characters, but with AL, CI, and FI about the same, and SI higher than in latipes × claviger. Minor differences from latipes × claviger in conventional characters are: antennal scapes slightly less clavate, petiolar scale crest a little less blunt, and slight color differences. The head and appendages are light yellowish brown; the rest of the body a darker brown. Only a small proportion of the latipes × claviger queens appear bicolorous; they range and average somewhat darker than latipes × coloradensis.