Myrmecocystus kennedyi

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Myrmecocystus kennedyi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Lasiini
Genus: Myrmecocystus
Subgenus: Endiodioctes
Species group: kennedyi
Species: M. kennedyi
Binomial name
Myrmecocystus kennedyi
Snelling, R.R., 1969

Myrmecocystus kennedyi casent0005412 profile 1.jpg

Myrmecocystus kennedyi casent0005412 dorsal 1.jpg

Specimen labels

Tolerant of a wide range of soil types, unlike many of its congeners, and shows a marked preference for nesting in patches of bare soil.

Identification

A member of the kennedyi group of the Myrmecoystus subgenus Endiodioctes.

Key to Myrmecocystus subgenus Endiodioctes species.

Worker - Malar area with fewer than three erect hairs in frontal view; head polished, sparsely pubescent; promesonotal hairs short, even in length, third tergum thinly pubescent; CI in excess of 90 in more than 85% of population. Female: Mesoscutum with large impunctate median area; parapsis with punctures of two sizes; penultimate segment of maxillary palp slender, parallel sided; malar area with few or no erect hairs; occiput with abundant fine punctures. Male: Lower lobe of aedeagus convex in profile; mesoscutum with shiny areas along midline; parapsis mostly polished and shiny; anterior mesoscutal hairs long. (Snelling 1976)

Keys including this Species

Distribution

United States, Mexico. Southern Idaho and Oregon south to northern Baja California and Sonora; western Utah and Arizona.

Distribution based on Regional Taxon Lists

Nearctic Region: United States (type locality).
Neotropical Region: Mexico.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Habitat

Known habitats for Myrmecocystus kennedyi range from Sagebrush Steppe and Great Basin Sagebrush in the north to Creosote bush-Bur sage and Palo verde-Cactus shrub desert in the south. Cole (l934a) noted that this ant (as melliger semirufus) is found in "... all parts of the desert region irrespective of the soil type ..." Since the present interpretation of kennedyi is more restrictive than previous interpretations, it follows that this no longer is strictly true. Thus, while kennedyi does exhibit a broad spectrum of nest sites, there is a decided preference for well-drained, coarse desert sands.

Biology

Snelling (1976) - Cole (1934b) found that in southern Idaho- nests were found in bare sandy areas between shrubs on small stable sand dunes. My own experiences parallel this observation: kennedyi tends to locate its nests in bare areas away from vegetation. Areas of dense grass, especially, seem to be avoided.

Nest tumuli of fully mature colonies may be as much as 20 cm in diameter, but rarely more than 6 cm high. These tumuli are usually in the form of very regular craters.

Wheeler (1908) reported finding workers tending pseudococcids (Orthezia sp.) near Needles, Calif. The pseudococcid Phenacoccus gossypii Townsend and Cockerell was found to be tended by kennedyi, near Gray's Well, Calif. (McKenzie, 1967). Shields (1973) found that larvae of the lycaenid, Philotes rita pallescens, were being tended by this ant near Currant, Nev. Specimens collected by the author south of Ravendale, Calif., were soliciting honeydew from an unidentified aphid feeding on Lupinus. In addition to soliciting honeydew from other insects, kennedyi very actively gathers nectar directly from floral and extra floral nectaries.

In addition to the above food sources, this species is also a general scavenger. The workers forage actively during the hot midday hours and secure large quantities of dead arthropods. Some are freshly killed and I have seen this species attack living insects. Those attacks which I have witnessed from inception are all similar to the following incident, observed near Mecca, Calif. on 13 Apr. 1963.

1311 hrs — Forager discovered live crab spider on ground under Sphaeralcea, grasped left fourth tarsus; spider attempted to dart away but ant pulled in opposite direction and impeded progress.

1314 — Second forager discovered struggling pair; attempted to grasp left third tarsus, but moved to opposite side, took hold of right third tarsus. Both ants now pulling backward.

1315 — Third ant joined, attached to left third tarsus; spider now being dragged toward nest about 1.5 m away.

1318 — Two more ants: one more on left third tarsus; one, after considerable "indecision" finally settled on right fourth tibia.

1319 — About 1.25 m from nest and another ant joined the attack, grasping first the right fore tarsus, but shaken off, managed firm hold on right second tarsus.

1320 — All ants now working concertedly to stretch prey and at same time move toward nest.

1321 — Two more ants, one on right second tarsus, one grasped side of abdomen in front of spinnerets.

1324 — About 0.5 m from nest; six or seven more ants, but they continually change holds on spider, now effectively "spread-eagled".

1328 — Spider carried down nest entrance by a mass of ants.

On another occasion a sphecid wasp, Ammophila sp., had "cached" a paralyzed lepidopteran larva while opening up her burrow. The caterpillar was discovered by a kennedyi worker which began to drag it away. The wasp, upon discovering the removal of her prey began a search, found it and began to drag it back toward the burrow. She was, however, driven off by the arrival of several more ants. Such "brigandage" may be fairly common.

Little is known about predation on honey ants by other animals. However, that horned lizards may occasionally prey on Myrmecocystus is indicated by an unpublished record before me. Mr. Lan Lester, Natural History Museum of Los Angeles County, found Phrynosoma platyrhinos feeding on kennedyi workers near Inyokern, Calif.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • kennedyi. Myrmecocystus kennedyi Snelling, R.R. 1969a: 6 (w.q.m.) U.S.A. [First available use of Myrmecocystus melliger subsp. semirufus var. kennedyi Cole, 1936b: 119; unavailable name.] See also: Snelling, R.R. 1976: 62.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Snelling (1976) - This is the species erroneously referred to as melliger semirufa by Wheeler (1908) and subsequent authors. As shown by Snelling (1969), melliger semirufa is a very different species, belonging to the melliger complex. Cole's name, described as a variety of melliger semirufa, is available and must be used for this common species.

Creighton (1950) placed melliger semirufa var. testacea, sensu Wheeler (1908) and subsequent authors, in the synonymy of semirufa (i.e .. kennedyi). Since the ant which Emery described as testacea is actually a senior synonym of mojave of the nominate subgenus, Snelling (1971) renamed testacea auctorum as wheeleri. Although related and superficially similar, there are numerous features by which kennedyi and wheeleri are separable, as discussed under the latter species.

The cephalic characters of this species show several interesting clinal variations. Gross head size averages larger in northern populations. While northern and southern populations both include the full range of variation, measurements from southern samples tend to be distributed in the lower half of the regression zone.

Overall eye size is of interest, too. Eye length increases by about 6% between the northern extremity of the range and the Mexican border. Below the border, there are too few samples to indicate a clear trend, but there appears to be a reversal. Thus, specimens from Idaho have an average EL of 0.244 mm, those from southern California average 0.267 mm and those from the Punta Penasco area of Sonora average 0.247 mm. The similar, and closely related nequazcatl has an average EL of 0.267 mm. The apparently reversed cline of kennedyi may be an example of "character displacement". However, until sympatric populations of the two species, if such exist, can be studied this phenomenon, as described by Brown and Wilson (1956) is not definitely demonstrated.

Description

Worker

Snelling 1976 figs. 100-108

Snelling (1976) - Measurements. HL 0.87-1.27 (1.17); HW 0.77-1.23 (1.07); SL 1.03-1.47 (1.37); WL 0.9-2.0 (1.6); PW 0.5-0.9 (0.7).

Head: Longer than broad to a little broader than long, CI 80-103 (91) (exceeding 90 in 88% of specimens measured), shorter than scape, SI 109-130 (117); sides, in frontal view straight or gently convex, slightly convergent toward mandibular insertions. Occiput, in frontal view, flat or slightly convex, without perceptible lateral angles. Eye small, 0.9-1.1 x first flagellomere; OMD 1.42-2.25 (1.88) x EL. Mandible with seven teeth.

Thorax: Slender to moderately robust, rarely robust, PW 0.37-0.67 (0.43) x WL; mesonotum, in profile, evenly sloping to metanotum. Propodeum about as high as long, basal face broadly rounded into posterior face.

Petiole: Thick in profile, summit rounded; in frontal view, crest narrow, convex, without median incision.

Vestiture: Pubescence fully appressed, very short, fine and sparse on head, a little more abundant on occiput. Denser on thorax, especially on sides, and propodeum. Dense and fully appressed on first two terga, extremely scattered on third and following segments.

Malar area usually with three or four short, fine, erect hairs near base of mandible, rarely two to four elsewhere; occipital hairs sparse, short, longest hairs equal to about 0.5 x MOD. Erect hairs sparse on thoracic dorsum, longest pronotal hairs not more than 0.5 x MOD. Propodeum with conspicuous erect hairs on basal and lateral faces, all hairs shorter than longest pronotal hairs. Crest and sides of petiole with sparse, short, erect hairs. Erect discal hairs of first two terga numerous, short, about as long as minimum thickness of hind tibia; longer, sparser, on following segments and ventrally. Scape with numerous fine, erect hairs on all except posterior surface, with interspersed subdecumbent to suberect finer pubescence. Femora and tibiae with numerous fine erect hairs on all except inner surface of fore femur.

Integument: Head moderately shiny, very lightly shagreened and with scattered fine, obscure punctures; frontal lobes more coarsely, closely and sharply punctate; clypeus polished, with scattered coarser punctures. Mandibles finely striate and with sparse, fine punctures. Thorax slightly shiny, closely micropunctate and shagreened. First two terga slightly shiny and closely micropunctate; third tergum shiny, almost polished, with scattered micropunctures and finely shagreened.

Color: Head, thorax and appendages clear light ferruginous. Gaster blackish to brownish, rarely with yellowish median blotches on first two terga (see Discussion).

Queen

Snelling (1976) - Measurements. HL 1.57-1.70; HW 1.64-1.87; SL 1.50-1.70; WL 3.4-3.9; PW 2.1-2.4.

Head: Sides straight, slightly convergent toward mandibular insertions; head broader than long, CI 105-109, slightly longer than, to as long as, scape, SI 95-100. Occiput, in frontal view, evenly and rather strongly convex from side to side, with no trace of lateral angles. Eye small, about 1.1 x first flagellomere; OMD 1.46-1.63 x EL. OOD 4.0-5.3 x OD, IOD 3.0-4.0 x OD. Penultimate segment of maxillary palp slender, parallel-sided. Mandible with seven teeth.

Thorax: Moderately to very robust, PW 0.57-0.71 x WL. Scutum and scutellum strongly flattened. Propodeum with strongly sloping basal face.

Petiole: In profile, compressed cuneate, apex acuminate; in frontal view, crest deeply angularly incised.

Vestiture: Pubescence diffuse on front of head and occiput, longer and denser on malar area, especially near base of mandible. Pubescence of thoracic dorsum sparse; longer and denser on sides and propodeum. Dense on gaster, producing noticeable sheen on first three terga, sparser on fourth segment.

Malar area with 1-6 erect hairs visible in frontal view; longest occipital hairs exceeding 0.5 x MOD. Longest mesoscutal hairs subequal to those of occiput; longest scutellar hairs exceeding MOD; longest pleural hairs shorter than those of scutellum. Propodeum with erect hairs about equal to those of mesoscutum present on basal and lateral faces. Petiole with sparse short, erect hairs on crest and sides. Terga with numerous short, fine, erect hairs discally, longer on succeeding segments and on sterna. Appendages with numerous fully decumbent to erect, short, fine hairs, except on posterior surface of scape and inner surface of fore femur, where subdecumbent to suberect pubescence is present. Wings without marginal fringes.

Integument: Clypeus shiny, with scattered coarse punctures; frontal lobes coarsely punctate, punctures separated by about a puncture diameter, interspaces smooth and shiny; except for sparsely punctate area before ocellar triangle, front of head coarsely and closely punctate, punctures separated by 2-3 puncture diameters; malar area with punctures coarse, close, mostly separated by a puncture diameter or less, tending to be linearly arranged, some elongate. Mesoscutum shiny, with scattered fine punctures, center of disc impunctate; parapsis finely punctate, punctures uniform in size, separated by up to twice a puncture diameter. Scutellum finely and sparsely punctate, especially along midline, shiny. Anepisternum moderately shiny, finely and sparsely punctate, interspaces finely shagreened; katepisternum duller, finely and closely punctate. Propodeum dull, finely and closely punctate, interspaces roughened. Summit of first tergum with dense micropunctures; discs of second and third terga similar.

Color: Head and appendages light ferruginous, gaster blackish; thorax usually mostly light ferruginous, but scutum and pleura may be brownish. Wings light brownish yellow, veins and stigma ferruginous.

Male

Snelling (1976) - Measurements. HL 0.78-0.86; HW 0.73-0.85; SL 0.86- 1.03; WL 1.8-2.1; PW 1.0-1.3.

Head: A little longer than broad to as broad as long, CI 94-100, shorter than scape, SI 108-120; in frontal view, sides straight, convergent toward mandibular bases; occiput, in frontal view, evenly arched, with barely perceptible lateral angle. OMD 0.82-1.00 x EL; OOD 2.8-4.0 x OD; IOD 2.5-3.5 x OD. Mandible without preapical notch or basal denticles.

Thorax: Robust, PW 0.56-0.68 x WL. Propodeum evenly sloping in profile, without basal face.

Petiole: Cuneate in profile, summit sharp; in frontal view; crest notched in middle or straight.

Vestiture: Pubescence everywhere sparse, except on pleura.

Pilosity short on front and vertex, a single hair in front of each lateral ocellus longer, exceeding 0.5 x MOD; hairs longer on side of head. Mesoscutal hairs numerous, stiff, longest less than MOD; some scutellar hairs a little longer; pleural hairs abundant, stiff, equal to those of scutum; propodeum with a few longer hairs on each side. Petiole with short erect hairs on sides and crest. Gaster with sparse long hairs. Scape, femora and tibiae with abundant, short, subdecumbent to erect hairs on all surfaces. Wings without fringe hairs on apical or posterior margins.

Integument: Malar area with close fine punctures, head otherwise polished, with scattered micropunctures; discs of scutum and scutellum polished and shiny, with scattered fine piligerous punctures. Pleura slightly shiny, integument roughened between fine punctures which are 2-4 puncture diameters apart. Propodeum moderately shiny and closely micropunctate on side, middle shinier, smooth and nearly impunctate. First three terga subpolished and shiny, with scattered micropunctures only.

Color: Blackish brown, mandibles, antennae and legs light brownish to yellowish. Wings faintly brownish, veins and stigma light yellowish.

Type Material

Snelling (1976) - Described from all castes from Indian Cove, nr. Hammett, Elmore, Co., IDAHO (A. C. Cole). Holotype and paratypes of all castes in Los Angeles County Museum of Natural History. Additional paratypes in American Museum of Natural History, Museum of Comparative Zoology, National Museum of Natural History.

References