Crematogaster sumichrasti

Occurring in a wide range of habitats, this ant can be abundant in mid-elevation urban areas.

Identification
Longino (2003) - In Costa Rica, sumichrasti is distinguished from the similar Crematogaster monteverdensis by the presence of one or more very long flexuous setae on the tibiae and by a more pronounced, almost tuberculate development of the juncture of the dorsal and posterior faces of the mesonotum. The only other species with similarly long macrosetae on the tibiae is Crematogaster flavosensitiva. The propodeal spines are upturned in sumichrasti, directed posteriorly in flavosensitiva.

I discovered the tibial pilosity character long after I had examined the types of sumichrasti, Crematogaster surdior, and Crematogaster atitlanica, and thus I am not positive of the character states on these types. However, six other collections from Mexico and Guatemala that I have recently examined all share the long tibial setae and tuberculate mesonotum characteristic of Costa Rica sumichrasti. Wheeler's illustration of subspecies Crematogaster maya shows a tuberculate mesosoma more like sumichrasti than monteverdensis. Forel's surdior was differentiated from sumichrasti mainly on the basis of color, but among the above mentioned Guatemalan and Mexican collections there is considerable variation in color, from light yellow to dark brown. Until there is further knowledge of character variation in northern Central America, I choose to consider maya and surdior synonyms of a widespread sumichrasti. In Costa Rica, collections are thorough enough to recognize a separate, microparapatric endemic species, monteverdensis. It is likely that similar patterns will emerge when additional collections are obtained and examined from other localities.

I have also chosen to treat Wheeler's atitlanica as a synonym of sumichrasti. Wheeler was collecting on the north shore of Lake Atitlan in Guatemala, in an area of open sandy soil in hot, dry conditions. He discovered two nests of Crematogaster under stones within about a mile of each other. Each of them contained about 100 adult workers, a small amount of brood, a large number of tiny apterous males, and one or three apterous adult queens respectively. The males and queens were apterous even in the pupal stage. Wheeler considered the workers nearly identical to sumichrasti (which did not stop him from describing them as a new subspecies). The queens and males were also very similar to sumichrasti, differing only in their aptery and, in the case of the males, in details of coloration.

I have found similar apterous males in monteverdensis, and the small polygynous queens of sumichrasti are not too different from the facultatively produced ergatogynes found in other Crematogaster species such as Crematogaster nigropilosa and Crematogaster curvispinosa. Given the frequency of ergatogynes in the genus as a whole and general indications of developmental plasticity, I suggest that social parasitism is unlikely to be the source of these apterous males. It is more likely to be an intraspecific phenomenon, perhaps facultative and associated with polygyny. We may discover that apterous males occur sporadically in a variety of species.

Distribution
Mexico to Costa Rica.

Distribution based on Regional Taxon Lists
Neotropical Region: Belize, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua.

Biology
Crematogaster sumichrasti occurs in a wide variety of habitats. It is most common in highly disturbed or urban areas at mid elevation sites, but can occur rarely in mature forest sites and low elevation sites.

Nests are in almost any kind of small cavity. I have collected nests from dead sticks and from cavities in the live stems of Acalypha (Euphorbiaceae). Ward collected nests in Mexico from dead sticks, a live vine stem, and from a swollen-thorn ant acacia. Skwarra (1934a,b), in her study of arboreal ant communities in the state of Veracruz, Mexico, found the species abundantly in a wide variety of nest sites including Cecropia internodes, orchid pseudobulbs, and between overlapping leaves of bromeliads. The types of Forel's surdior were tending aphids beneath the leaf-sheaths of banana (Forel 1885). The types of Wheeler's atitlanica and Crematogaster maya were collected beneath stones in a very dry, open area in Guatemala.

Colonies are polygynous and can have large numbers of dealate queens. Skwarra reported one colony with 31 dealate queens and 962 workers, and another colony with 164 dealate queens and about 1200 workers.

In Costa Rica, sumichrasti is very common in urban areas in and around the capital, San José. I have found it as an abundant ant in the backyard patios and gardens of several hotels and other dwellings. In these circumstances I have observed columns of workers and dispersed foragers on the vegetation, active both day and night. It is a somewhat less abundant ant along the upper parts of the road from the PanAmerican Highway to Monteverde, where I found small nests in dead sticks along the road edge. A collection that seemed out of place relative to my other observations was a small colony in a live stem of an Acalypha shrub in Hitoy Cerere Biological Reserve, a lowland rainforest site on the southern Atlantic slope. This small colony contained 23 workers and one dealate queen. Finally, a lone worker was collected in a mature wet forest site at 1000m elevation in Braulio Carrillo National Park, on the Atlantic slope of the Cordillera Volcanica Central. The ALAS project carried out an intensive program of sampling at this site, and out of 100 two-week Malaise samples obtained from a set of 20 traps, one sumichrasti worker was found.

Nomenclature

 *  sumichrasti. Crematogaster sumichrasti Mayr, 1870b: 993 (w.) MEXICO. Forel, 1908b: 46 (q.m.). Combination in C. (Orthocrema): Emery, 1922e: 136. Senior synonym of atitlanica, maya, surdior: Longino, 2003a: 114.
 * surdior. Crematogaster sumichrasti st. surdior Forel, 1885a: 375 (w.q.) GUATEMALA. Combination in C. (Orthocrema): Emery, 1922e: 136. Raised to species: Dalla Torre, 1893: 87. Subspecies of sumichrasti: Forel, 1899c: 82; Emery, 1922e: 136; Kempf, 1972a: 89. Junior synonym of sumichrasti: Longino, 2003a: 114.
 * atitlanica. Crematogaster (Apterocrema) atitlanica Wheeler, W.M. 1936c: 47, fig. 1 (q.m.) GUATEMALA. Wheeler, G.C. & Wheeler, J. 1960b: 13 (l.). Junior synonym of sumichrasti: Longino, 2003a: 114.
 * maya. Crematogaster (Orthocrema) sumichrasti subsp. maya Wheeler, W.M. 1936c: 48, fig. 1 (w.) GUATEMALA. Junior synonym of sumichrasti: Longino, 2003a: 114.

It should be noted that Crematogaster atitlanica, currently considered a junior synonym of this species, is listed by the IUCN as vulnerable. See the IUCN website for details.

Worker
Longino (2003) - HL 0.675, 0.563, 0.750; HW 0.751, 0.606, 0.789; HC 0.673, 0.544, 0.730; SL 0.608, 0.525, 0.664; EL 0.182, 0.161, 0.189; A11L 0.245; A11W 0.138; A10L 0.102; A10W 0.121; A09L 0.067; A09W 0.093; A08L 0.052; A08W 0.069; WL 0.801, 0.625, 0.883; SPL 0.157, 0.119, 0.151; PTH 0.181, 0.149, 0.197; PTL 0.244, 0.196, 0.253; PTW 0.220, 0.163, 0.231; PPL 0.189, 0.152, 0.192; PPW 0.242, 0.197, 0.258; CI 111, 108, 105; OI 27, 29, 25; SI 90, 93, 89; PTHI 74, 76, 78; PTWI 90, 83, 91; PPI 128, 130, 134; SPI 20, 19, 17; ACI 0.24.

Color yellow orange; workers monomorphic in size.

Mandibles striate; clypeus with two to four longitudinal carinulae at anterior margin, anterior margin gently convex; head about as long as wide, subquadrate, with emarginate posterior border; antenna with terminal two segments enlarged to form a club, third segment from end somewhat enlarged, blurring distinction between two and three-segmented club; scapes with abundant long erect setae; when scapes laid back from antennal insertions, they barely surpass margin of vertex; face smooth and shining, with variable extent of striated region between antennal insertion and eye, and whorled above antennal insertion; face covered with abundant long flexuous white setae, no appressed pubescence; in face view abundant setae project from lateral and posterior margins.

Pronotum in lateral profile convex; dorsal face of mesonotum long, flat, somewhat produced, posterolateral margins almost tuberculate, posterior face short, dropping abruptly to propodeal suture; propodeal suture deep in dorsal view but may be more or less obscured in profile due to lateral carinulae that bridge the suture; propodeum with very short, weakly differentiated dorsal face and long posterior face; propodeal spines long, spiniform, upturned; pronotal dorsum mostly smooth and shining, with faint traces of longitudinal carinulae; dorsal face of mesonotum with strong parallel lateral carinae, terminating posteriorly at almost tuberculate juncture with carinulae extending down posterior face, across suture, and onto bases of propodeal spines; medial mesonotum concave, smooth and shining; posterior face of propodeum flat to concave, smooth and shining; side of pronotum smooth and shining; katepisternum and side of propodeum shining, largely smooth with traces of feeble carinulae; mesosomal dorsum with abundant long flexuous amber setae, setae on pronotal humeri and posterolateral mesonotal tubercles very long, subequal in length, longer than anterolateral mesonotal setae; tibiae with abundant long erect setae, of variable length, one or more tibial setae very long, subequal to twice maximum tibial width.

Petiole in side view trapezoidal, smooth and shining or faintly microareolate, with minute right-angle or rounded anteroventral tooth; dorsal face of petiole smooth and shining, longer than wide, widest posteriorly, sides weakly convex, gradually converging to level of petiolar spiracles, abruptly narrowed anterior to spiracles, with about six long amber setae along posterior border; postpetiole with minute subacute to right-angle anteroventral tooth, postpetiole in dorsal view subquadrate and wider than long, with abundant long erect setae; fourth abdominal tergite smooth and shining, with abundant long flexuous erect amber setae, no appressed pubescence.

Queen
Longino (2003) - A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum) with general shape, sculpture, and pilosity characters of the worker; size characters as in Figures.

Type Material
Longino (2003) - Syntype workers: Mexico (Sumichrast, Norton) (examined, Norton worker here designated LECTOTYPE).