Solenopsis molesta species complex

The following is based on: Pacheco, J.A. & Mackay, W.P. 2013. The systematics and biology of the New World thief ants of the genus Solenopsis (Hymenoptera: Formicidae). Edwin Mellen Press, Lewiston, New York. 501 pp. PDF

Solenopsis molesta Species Complex / Key to workers / Clave a las obreras

This is a group of New World thief ants in the genus Solenopsis.

Diagnosis - These species bestow thief ants the reputation of being difficult to identify, as they are all small to medium sized, yellow ants (with a few exceptions of dark brown to black coloration), in which the worker caste is morphologically very similar. The head is longer than wide, usually slightly elongate, but can be quadrate. These species are nearly devoid of sculpturing with nearly all body surfaces smooth and shiny. When sculpturing is present it consists of horizontal striae on the metapleuron, occasionally on the mesopleuron, petiole and postpetiole. In the majority of the species, the cephalic punctures are fine and difficult to see, but in a few species the punctures are semi-coarse (however not as coarse as in the members of the fugax species complex). There are typically only two teeth (the lateral teeth) along the anterior clypeal border with an occasional swelling in the extralateral position that is angulate in some instances (Moreno-Gonzalez, 2001). The petiole is wider than the postpetiole viewed laterally with an occasional subpeduncular tooth present ventrally. The postpetiole is oval and about as wide as the petiole or larger than the petiole when viewed dorsally.

Workers are very difficult to identify without females. For example, workers of Solenopsis castor, S. conjurata, S. corticalis, S. gnoma, S. nickersoni, S. picta, S. subtilis, S. sulfurea, S. tenuis and S. zeteki are nearly identical. Likewise the workers of S. basalis, S. clytemnestra, S. decipiens, S. franki, S. helena, S. joergenseni, S. laeviceps, S. latastei, S. loretana, S. major, S. molesta, S. parva, S. picea, S. quadridentata, S. rosella, S. salina, S. striata and S. validiuscula are difficult to separate. Workers of a third group, consisting of S. abdita, S. abjectior, S. carolinensis, S. maboya, S. orestes, S. patriciae, S. pollux and S. texana are nearly impossible to separate. Unfortunately the workers are often collected without females, especially in series from baits, pitfall traps and litter samples. The differences among the females suggest that they are all valid species and the females are usually necessary for accurate identification. Consequently, it has been necessary to recognize three subgroupings; the molesta, pollux and tenuis subgroups to facilitate identification. Workers of the molesta subgroup are relatively large (1.4-2.0 mm) in total length, moderately hairy and ranging from yellow to black in coloration. The pollux subgroup is small to relatively large (l.0-1.5 mm) in total length, very hairy and yellow to medium brown in color. The tenuis group is small to relatively large (1.0-1.6 mm) in total length, not hairy to moderately pilose and yellow to dark brown in coloration.

The minor worker of S. tetracantha (also placed in the fugax species complex) is placed in the South American key as it may be confused with workers of the pollux subgroup. Due to the great similarity in the worker caste form, a reference collection of these species may be necessary for correct identification.