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Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

The text below is mostly taken directly from a revision of the species of Central America (Longino and Snelling 2002). Literature cited is not included in individual species accounts and there are no links from citations to individual references. Instead I have posted a single document with literature cited for all the Procryptocerus pages. See Literature Cited.
The genus Procryptocerus is endemic to the Neotropics, from southern Mexico to northern Argentina. It does not occur on any islands except those immediately adjacent to the mainland (e. g. Trinidad). It is always a low density element of tropical forests and is never dominant or conspicuous. Cephalotes, to which it is closely related, is much more common and conspicuous, especially in lowland habitats. Procryptocerus extends to higher elevations than Cephalotes. In mid-elevation cloud forests, just above the elevational limits of Cephalotes, Procryptocerus can become relatively abundant and conspicuous. Colonies are always small and foraging rates seem to be low. Foragers are solitary and very low density. Nests are in hollow dead or live stems. No species are known to be specialized plant ants, although opportunistic nesting in ant plants is common.

The genus can be separated from Cephalotes by the combination of the following worker and queen characters: (1) antennal scrobe extending almost to margin of vertex, (2) eyes situated below the scrobe, (3) frontal carinae not covering the genae from above, (4) pronotum without spines or teeth, (5) metatarsus not compressed, and (6) petiole and postpetiole without projecting spines, teeth, or tubercles (Kempf, 1951). Barry Bolton recently informed me of two other characters: Procryptocerus have a stridulitrum and the eyes are relatively far forward on the head; Cephalotes lack a stridulitrum and the eyes are situated relatively far back. Procryptocerus workers are strictly monomorphic (Wheeler, 1984). The larvae of several species of Procryptocerus have been described by Wheeler & Wheeler (1954, 1973), but no features unique to the genus have been identified. Although the above characters allow a clean separation of Procryptocerus and Cephalotes, it remains unknown whether any of them are synapomorphic. Thus it is unknown whether Procryptocerus is monophyletic or the paraphyletic remainder of the Cephalotini after Cephalotes is removed.

Kempf (1951) revised the genus, and subsequently published short addenda describing new species, making minor taxonomic changes, and providing new locality data (Kempf, 1957, 1960, 1964a, 1964b, 1969). Longino and Snelling (2002) revised the genus for Central America.

For those needing to identify South American Procryptocerus, a combination of this key and Kempf (1951) will serve to identify many of the common species, especially in Amazonia and southeastern Brazil. However, northern South America and the Andes are poorly collected, and many taxonomic problems remain in these regions.

The key is based on workers. Queens are similar to workers in most respects. Queen head width is 1 to 1.16 times worker head width. The face sculpture is usually the same, although subtle differences may occur. The main differences are the caste-specific structural differences of the mesosoma.

Terminology and abbreviations.

The head is assumed prognathous. The mandibles and clypeus are anterior. The face (= frons) is dorsal. The vertex is posterior. The occiput and genal bridge are ventral. The face and vertex are often sharply differentiated, meeting at an angle. The juncture is termed the vertex margin. The vertex is delimited ventrally by the occipital carina. In "face view" the anterior margin of clypeus and margin of vertex are in the same plane of focus.

An important character system that may have phylogenetic significance is the structure of the frontal carinae and their relationship to the torulus. In some species the frontal carina is a thin flange that forms the upper scrobe margin, continues above the torulus, curves medially, and continues onto the clypeus as a lateral carina. The carina is separate from the dorsal margin of the torulus. A character series can be seen in which the carina becomes thinner where it crosses the torulus, eventually becoming discontinuous from the lateral clypeal carina, and fusing with the dorsal margin of the torulus. The frontal carina then appears to end on the torulus. This is accompanied by a thickening of the margin of the frontal carina just posterior to its contact with the torulus.

True abdominal segment one is the propodeum, segment two is the petiole, segment three is the postpetiole. Subsequent segments comprise the gaster. The posttergite (sensu Bolton, 1994) of abdominal segment four is referred to as the first gastral tergite. Pretergites and posttergites of gastral segments two, three, and four are sharply differentiated by a pronounced carina. The pretergite is smooth and shiny; the posttergite is variously sculptured. The posttergite of the first gastral segment and the pretergite of the second are very tightly overlapping, and it may appear that the posttergite has a thin, smooth band at the posterior margin. In other words, the juncture between the pre- and posttergites of the second gastral segment may be mistaken for the posterior margin of the first gastral segment.

Sculpture terminology generally follows Harris (1979). The following measurements are reported:

AL: Length of first gastral tergite, measured in dorsal view, along median axis, from line tangent to humeral margins, to posterior border (n.b. do not confuse pretergite of second segment with postergite of first, see above).

ASW: Width of striae on first gastral tergite, calculated by measuring width of a group of striae that cross medial 1/4 of width, at a point between the petiolar insertion and mid-disc that is regularly striate (typically half way between), and dividing by the number of striae in the group.

AW: Width of first gastral tergite at widest point, measured in dorsal view.

EL: Maximum diameter of eye.

HL: Head length, measured along median axis, from line tangent to rearmost points of margin of vertex, to anterior clypeal margin on median axis (not to lateral extentions of clypeus).

HW: Head width, measured across the widest part of the head (not including eyes) in face view, just posterior to antennal scrobes.

MeL: Length of mesosoma, measured from the anterior margin of the pronotum (not including "neck") to the tip of a propodeal spine, in dorsal view.

MeW: Width of pronotum, measured across the widest part of the pronotum, in dorsal view.

MFL: Metafemur length; anterior or posterior view, measured along longitudinal axis from ventral juncture of femur and trochanter to distal extremity of femur.

MFW: Metafemur width; anterior view, perpendicular distance between lines parallel to longitudinal axis used for MFL and tangent to dorsal and ventral borders of femur.

MTL: Metatibia length, measured along exterior surface, not including basal condyle.

PpW: Postpetiole width, measured in dorsal view.

PrL = Length of dorsal face of propodeum, measured along median axis, from approximate center of propodeal suture, to approximate juncture of dorsal and posterior faces (corresponding to base of imaginary parabola formed by extending inner margins of propodeal spines).

PrS = length of propodeal spines, measured along median axis from posterior point of PrL to point perpendicular to tip of longest propodeal spine.

PrT = PrL+PrS. PrL and PrS are always measured at the same time, such that the end-point of PrL is the starting point of PrS. Because of the subjectivity of the posterior margin of the dorsal face of the propodeum, PrL and PrS are somewhat poorly defined, but PrT has more precise anterior and posterior boundaries.

PrW: Width of propodeum, dorsal view, across widest part anterior to propodeal spines (including basilateral lobes if present).

PtH: Petiole height, measured in lateral view, perpendicular to line from anterodorsal to posterodorsal margin, from summit of dorsal convexity to ventral margin.

PtL: Petiole length, in dorsal or lateral view, from anterodorsal to posterodorsal margin.

PtW: Petiole width, measured in dorsal view across widest point.

SL: Scape length, from distal end of shaft to lower edge of skirt which flares over basal condyle and neck.

Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu

Date of this version: 6 December 2002.

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