Lasius claviger

This species exhibits temporary social parasitism. Queens found new colonies by infiltrating an established nest of another Lasius species, killing the queen and using host workers to care for her initial brood.

Distribution
Southern New England to Minnesota, south to Kansas and east to Florida.

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



Biology
This section is reported, slightly modified, from Wing (1968).

Habitat data in varying degrees of completeness were associated with 137 of the 486 samples of claviger. Samples collected in woods numbered 78, those in the open, 30, those of uncertain origin, 29. With respect to immediate nest-cover, 45 were under stones, 21 associated with logs and stumps, 1 came from a grassy mound, 30 with miscellaneous or no cover, and 40 of uncertain status. One of the 30 nests in the miscellaneous category was under a beef marrow bone in a backyard in Ithaca, New York.

In addition to the data associated with specimens received for study; Carter (1962b) and Talbot (1963) have published data based on a large number of colonies. Carter found claviger common throughout North Carolina except in the Coastal Plain. Nests were located under stones, in well-decayed stumps, and without cover in a variety of soil types ranging from red clay to loose sand. They occurred in fields of various ages and in forests ranging from young to mature. The forests were composed of various species of pines, oaks, and hickory. Talbot, working in southern Michigan, found claviger versatile in its nesting habits. Nests were about equally frequent in deep woods, open woods, and fields. In deep woods, most nests were associated with logs and stumps. In open woods, stones and old logs usually formed the immediate nest-cover. Nests located in the open often were not associated with stones or wood; small mounds frequently marked their location. The soil thrown up at the time of flight probably was overgrown with grass, eventually becoming permanent mounds. Some of them were up to 3 feet in diameter and 2 to 4 inches high. My own field observations on claviger, principally in Minnesota, New York, and North Carolina, indicate that the location and immediate cover of nests varies somewhat from one local to another. Before more precise quantitative statements than those indicated above can be made, a number of habitats in various parts of the range need to be uniformly investigated.

Reproduction
Annual sexual cycle June may be taken as a starting point for the cycle of this species. During June and July most records of sexual forms in nests are based on queen larvae and pupae. The immature stages of queens were investigated in claviger to determine their seasonal distribution as closely as possible. It is estimated that 6 weeks to 2 months elapse from the first appearance of queen larvae to the time when adult queens are found in the nest. The timing for males is probably similar to that of females. Investigation of the seasonal distribution of the sexual immatures of other taxa was done far less exhaustively than in claviger. It is likely, however, that the estimate for claviger will hold for other taxa producing alates during the warmer months of the year.

By August, mature claviger nests contain adult alates in sizable numbers. These nests remain relatively numerous on into October. Most nuptial flights begin in September and continue into November, with a few occurring earlier and later.

Associated with flights is the appearance of many dealate queens. In claviger, unlike other species, the dealate queens remain numerous until the end of the following April, when they suddenly disappear. claviger infests buildings infrequently, so most of these queens are collected out-of-doors, either singly or in groups. Occasionally they are associated with alate females, and more rarely with males. They are found in woods or fields under trash, stones, logs, or other cover. It is evident that large numbers of dealate queens of claviger regularly overwinter in all or most parts of the range. The reasons for their sudden disappearance in late April are unknown. Intensive field studies of this species during the spring months might well lead to an understanding of its method of colony foundation. At worst such field studies stand a chance of turning up clues that could help in designing experiments to test likely alternatives.

claviger is one of the two species with a sexual cycle that spans most of the year. The chief reason for this extensive time-range is the continuing abundance of overwintering dealate queens, which occur long after normal flight activities are over.

Talbot (1963) reported that extreme claviger flight dates at Tiffin, Ohio were September 11 and 25 during the period from 1933 to 1944. Buren (1944) reported flights during late August, September, and October in Iowa. Groskin (1947) reported an unusually late flight of claviger on December 3, 1963 in Pennsylvania. Talbot's observations at the Edwin S. George Reserve in Livingston Co., Michigan began in early June and ended in early September each year. The first date on which she found a claviger nest with adult alates was August 20. In commenting on her flight observations in Ohio, she stated that rains induced the workers to open the nests. Flights took place in mid-afternoon, and were favored by decreasing light, warmth, and high humidity. The nest observed during the flight of September 22 still contained males and females on October 21. Because of this observation, she surmised that the alates may have overwintered in the nest and flown during the next spring. Since flights are known to occur later than October 21, it does not necessarily follow that this colony failed to empty its nest of alates during that year. Even when a few alates do overwinter in parental nests, there is no reason to assume that this results in flights during the following spring. To my knowledge no spring flights have been observed for claviger.

Associations with other Organisms
Nest Guests In addition to the 2 or 3 dozen vials with aphids and coccids, and a few with mites, the following papers listed other insects associated with claviger: Evans (1961), Pseudisobrachium ashmeadi and P. elongatum (Hymenoptera: Bethylidae). Schwarz (1890), Batrisodes montrosus, B. ferox (Coleoptera: Pselaphidae), Panagaeus crucigerus (Coleoptera: Carabidae), Quedius molochinus, Homoeusa expansa (Coleoptera: Staphylinidae), and the larvae of Brachyacantha ursina (Coleoptera: Coccinellidae), which were preying on the Pemphigus pastured by the ants. Wickham (1898), Batrisodes frontalis found in the galleries of a nest under a log. Park (1935), Batrisodes globosus. Park (1932) studied the myrmecocole, Batrisodes globosus in a Lasius americanus (prob. = alienus) colony. He concluded that this species may act occasionally as a predator of living host larvae, but more frequently aids the host colony by disposing of dead larvae. The habits of B. globosus are probably similar in the colonies of the closely related L.claviger.

Nomenclature

 *  claviger. Formica clavigera Roger, 1862a: 241, pl. 1, fig. 13 (q.) U.S.A. Mayr, 1870b: 950 (w.m.); Wheeler, G.C. & Wheeler, J., 1953c: 155 (l.). Combination in Acanthomyops: Mayr, 1862: 700; in Lasius: Mayr, 1870b: 950; in Lasius (Acanthomyops): Emery, 1893i: 642; in Acanthomyops: Donisthorpe, 1916c: 276; in Lasius: Ward, 2005: 13. Senior synonym of parvula: Wing, 1968: 67. See also: Creighton, 1950a: 429; Regnier & Wilson, 1968: 955; Smith, D.R. 1979: 1440.
 * parvula. Lasius (Acanthomyops) parvula Smith, M.R. 1934b: 213 (w.) U.S.A. Combination in Acanthomyops: Creighton, 1950a: 432; in Lasius: Ward, 2005: 13. Junior synonym of claviger: Wing, 1968: 67.

Worker
Wing (1968) - Body size and pilosity moderate, pubescence dilute to moderate. Crest of petiolar scale sharp to moderate, usually distinctly to feebly emarginate. Separated from Lasius interjectus by the more or less uniform distribution of standing hairs over dorsum of gaster and by lower SL. Separated from Lasius latipes by the conformation of the petiolar scale, and standing hairs usually confined to posterior 2h of gula. Separated from Lasius californicus by SI usually 80 or less. Separation from Lasius coloradensis is difficult as discussed in the treatment of variation of that taxon.

Standing body hairs simple to barbulate, moderate to numerous, of variable length, but most not extremely short. In most specimens, standing femoral hairs are largely confined to the fore femora. Pubescence variable, moderate at base of gaster, more dilute on its dorsum; that on front of head very dilute to moderate, but rarely more dense than at base of gaster. Body surface usually at least feebly shining. Body varying in appearance from robust to slender, the smaller specimens usually appearing at least fairly slender. Body and appendages pale yellow to brown.

Queen
Wing (1968) - Head not deformed. Antennal scapes and funiculi weakly clavate to clavate, antepenultimate segment of funiculus not over 1.55 times wider than long. SI not over 66, usually 63 or less. Body size moderate; HW at least 1.22, and usually 1.38 mm or more; AL ranging from 2.08 to 2.82 mm, usually over 2.25 mm. FW 0.33 to 0.51 mm; fore femora without genual plates; FI 33 to 42. Crest of petiolar scale sharp to moderately sharp, usually distinctly emarginate. Scale covered with 45 or fewer standing hairs. Gula with standing hairs usually confined to its posterior 2/3, and usually numbering less than 24, their maximum length rarely over 0.30 mm. Pilosity on dorsum of gaster: (1) confined to rows on posterior edges of tergites beyond first, or (2) more or less evenly distributed over entire surface, or (3) exhibiting a pattern intermediate between these two. Pubescence on head and gaster usually dilute, occasionally moderate, usually more dilute on head than on gaster. Body color medium to dark brown, not appearing black to naked eye.

Standing body hairs simple to finely barbulate. Most standing femoral hairs on fore femora. Most of body surface shining, often strongly so. Appendages usually lighter in color than body.

Male
Wing (1968) - Scapes slender to somewhat clavate. AL usually 1.60 mm or more, HW often 1.00 mm or more, SL usually 0.65 mm or more. Terminal width of pygostyle 0.04 mm or more. Width of petiolar scale through spiracles at least 1.5 times its height above spiracles. Pubescence dilute to moderate. Body color brown to moderately dark brown, but rarely dark enough to appear black or nearly black to naked eye.

Standing body hairs simple to minutely barbulate, usually moderate in number. Body surface usually shining. Color medium reddish brown to dark brown, head and alitrunk often darker than gaster, appendages lighter.

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

Lasius latipes × claviger hybrid
This sporadic form is recorded in a band from Minnesota and Central Illinois east to New England and New Jersey. It is by far the most common of all known hybrid taxa, most of which are known from only one or two collections.

Worker
Intermediate between latipes and claviger, but having the general appearance of latipes, from which it is not now reliably separable.

Pubescence on gaster dilute to dense. Petiolar scale variable, but usually quite similar to that of latipes. Standing hairs on gula almost invariably cover the entire surface. Length of standing body hairs and body size average and range a little greater than in latipes. Body color yellow to brownish yellow.

Queen
Intermediate between latipes and claviger. Head not or only slightly deformed. Antennal scapes and funiculi decidedly clavate; antepenultimate segment of funiculus greater than 1.55 and less than 2.30 times wider than long. Entire surface of gula covered with from 24 to 40 standing hairs, with maximum length usually less than 0.30 mm. FW 0.50 to 0.75 mm, usually at least 0.55 mm; genual plates of fore femora moderate, not conspicuous. FI 43-54. Crest of petiolar scale usually blunt to very blunt, not emarginate, rarely sharper and feebly emarginate. Scale covered with 50-75 standing hairs. Most standing femoral hairs confined to fore femora.

Pubescence on gaster from very dilute to very dense, that on rest of body usually much less dense, most of body usually shining. Pilosity on gaster variable, but most specimens have standing hairs largely confined to the posterior edges of tergites beyond first. Body color variable, most frequently a medium-dark castaneous brown. Some specimens are lighter yellowish brown, others are a dark grayish brown.

Male
Typical of the males of latipes in all known respects.

Type Material
Wing (1968) - Type locality: Pennsylvania. Location of type: The type specimen, a queen bearing the locality data "Pennsylvanien", is in the collection of the Institut fur spezielle Zoologie und Zoologisches Museum der Humboldt-Universitat, Berlin. The type, probably collected by Schaum near Philadelphia, is more or less intermediate between the "typical" and "variant" forms. The distribution of standing hairs on the dorsum of the gaster is that of the "typical" form. The antennal scapes and funiculi are weakly clavate, as in the "variant" form. Most of the standardized measurements fall in the midrange of the "variant" form. The 2 other queens mailed to me for examination bear "Nordamerika" labels. They appear to represent samples from separate localities, both of which are probably different from that of the type.