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Extant: 10 valid species
Fossil: 3 valid species
> CylindromyrmexHNS: Menozzi, 1931: 191 - 195, key to spp., p. 194 ----- Santschi, 1932: 410 - 412, MetacylindromyrmexHNS doubtfully distinct, p. 411. ----- Wheeler, 1937: 441 - 445, includes key to [[ worker ]] [[ queen ]] species, p. 444; virtual synonymy of MetacylindromyrmexHNS, p. 443.
Worker: Essentially monomorphic but varying considerably in size, even in uninidal series. Color reddish brown to black or piceous; appendages yellow to black, or dark with the tibiae extensively marked with yellow or ivory. Integument thick and hard.
Head longer than broad, and deep dorsoventrally; sides parallel, with blunt posterior corners and concave posterior border. Clypeus short, crowded by the antennal insertions and the frontal carinae, which approach or reach the anterior margin of the head; in the latter case, the median section of the clypeus is vertical. Posteromedian section of clypeus extending posteriad between the nearly approximate frontal lobes as a deeply sunken groove that broadens very slightly behind to encompass the tiny frontal area, which is not or barely distinguishable. Frontal carinae subparallel behind, where they arise more or less near the cranial midlength, curving mesad anteriorly to form a rounded plate or twin blunt points at or above the main part of the clypeus. The carinal lobes are extended laterad in the form of broad laminae roofing the medial sides of broad antennal scrobes that extend forward from the level of the eyes to the antennal insertions. Behind median groove, space between carinae is broad, flat, or gently convex. Ocelli present or absent. Antennae very short, broad, and flattened, 12 - merous; scape only about 2 - 3 times as long as broad, and not, or just barely, reaching the eye; funiculi gradually broadened toward apices; a vague club formed of the 3 apical segments, or no club distinguishable; apical segment as long as, or longer than, the 2 preceding segments taken together. Mandibles subtriangular, thick and slightly downcurved; apical and basal borders distinct and meeting at an angle; apical border with 4 - 10 low teeth or crenulations, sometimes virtually edentate, but with a more or less acute apex. Maxillary palpi with 2 segments, labial palpi with 2 or 3 segments; mouthparts of C. striatusHNS described by Gotwald 1969: 43, 47, pl. 31. Compound eyes situated near or behind cranial midlength, ranging from small and flat, with 20 or less indistinct facets, to large and moderately convex, taking up nearly 1 / 3 length of the sides of the head and having 500 or more facets.
Trunk elongate, boxlike, with subparallel, vertical sides and a gently convex dorsum (sometimes nearly flat); dorsal sutures represented at most by a feeble, promesonotal, arched line and a weakly indicated metanotal groove with a median pit, but often these sutures are obliterated. Lateral sutures reduced to an inverted U- or A-shaped system outlining the mesopleuron. Pronotum not transversely marginate in front, humeral angles rounded; propodeal declivity distinct and flat or nearly flat, but not, or bluntly, margined laterally and above. Propodeal spiracle situated below the middle axis of the trunk, round, oval, or elliptical, opening directed dorsad and usually slightly caudad. Metapleural gland opening a horizontal slit very near the bottom edge of the trunk (below a rather prominent bulla); a horizontal groove extends forward along the lower side of the trunk to the vicinity of the mesometanotal suture.
Petiolar node subcuboidal, usually a little longer than high and about as broad as long, a little broader behind than in front, sides slightly convex and vertical (receding ventrad); subpetiolar process stout and bluntly angular in front, subsiding concavely behind. Postpetiole much wider than petiole, wider than long, and almost as wide as succeeding (first gastric) segment, from which it is separated by a wide pretergital belt belonging to the latter; constriction between these two segments is marked, especially in side view. Stridulatory file present and extremely fine on middle of first gastric segment pretergite but not readily visible unless gaster is flexed.
In C. striatus, GotwaldHNS (1969: 126) found the tergum and sternum of the postpetiole (true abdominal somite III) to be fused, while in the succeeding segment, which I call the " first gastric " in this paper, the tergum and sternum are connected only by membrane, as are those of the segments following. The first gastric segment is larger than the postpetiole and the second and third gastric segments, but not markedly so, and these segments are well developed, mobile, and extend free. Apical (VII true abdominal) somite well developed, tapered caudad, the tergum flattened (obliquely truncate) and margined along the sides with subreclinate spinules that appear to be short, stout setae in raised sockets, arranged on each side in a more or less regular single row. The pygidium itself ends in a pair of blunt, flattened teeth lying just above the sting, which is well developed and tends to be curved in a sword shape (laterally compressed) and usually is extruded part way.
Legs stout, moderate to short in length; femora dorsoventrally incrassate and anteroposteriorly compressed, their flexor surfaces with a long, deep sulcus to receive the curved flexor surface of the tibia when the leg is folded. Tibiae more or less incrassate, especially in the assumed cryptic-foraging small-eyed species; apical spurs long, broadly pectinate, especially on foreleg; middle and hind legs each with an extra, small, pectinate outer spur next to the large one.
Metatarsus, especially that of middle leg, extremely variable in proportions: long and slender in C. striatusHNS, much shorter and broadened apically in the small-eyed species, with a semicirclet of 4 - 5 stout, spinelike setae on the outer apical edge, best developed also in the smalleyed species, where the middle legs may serve (along with the pygidium) as " pushers " in helping the ant through narrow cracks or passages in soil or rotten wood, perhaps through defensive walls being raised by termite prey.
" Pusher legs " are also found in the termite predators of tribe AcanthostichiniHNS, in genera CentromyrmexHNS and " Wadeura " ( PachycondylaHNS) of tribe PoneriniHNS, in CryptoponeHNS (prey unknown) of the same tribe, and in the termitotherous myrmicine genus MetaponeHNS; in MelissotarsusHNS, similar middle legs bear glands that may have a very special use in marking trails along the substrate above the ant's body as it moves along (see Delage-Darchen, 1972, Insectes Sociaux 19: 213 ff.).
Other tarsal segments also with 2 - 5 spinelike setae at apices. Claws simple, thickened basally.
Queen: Like the worker, and usually only moderately larger. Compound eyes larger, and pterothorax developed, but with a flat dorsum continuing the flat or feebly convex dorsal surface of the trunk.
Male: Similar in size to the conspecific worker, but body more slender; head shorter, subglobular, with very large convex eyes taking up more or less the anterior half of the sides of the head. Antennae long and slender, 13 - merous, with very short, cylindrical scape, even shorter, cup-shaped pedicel, and remaining flagellar segments long and subcylindrical. Frontal lobes short, raised, separated in front, but fused behind. Clypeus with a broad, sloping anterior part and a narrow posterior part between frontal lobes. Mandibles substantial, narrow-subtriangular, with curved, edentate (cultrate) apical margins and an acute, incurved apical tooth. Mandibles crossing over each other at full closure, leaving no anteclypeal space. Palpi segmented 2,2 or 2,3. Trunk compact and subcylindrical, pterothorax only gently convex and slightly raised above truncal outline. Notauli present ( C. parallelusHNS) but incomplete behind, not meeting as a Y or V. Metanotum small, transversely elliptical. Propodeum long, declivity nearly perpendicular and with a very strong margin and a vertical median septum or carina. Wings with complete ponerine venation, but Mf 2 and r-m have wide breaks, apparently at the crossings of a fold line; radial cell fairly short, closed apically at or very near the margin. Pterostigma thick, convex, heavily pigmented. Hind wing with distal free abscissae ending near mid-wing; r-m weak and broken; anal lobe lacking. Legs short and only moderately robust; anterior and middle coxae inserted far apart. Middle and hind tibiae each with 2 pectinate apical spurs, one larger than the other. Tarsal claws simple but with thickened, sometimes angular bases. Petiole much like that of worker; anterior face steep and marginate. Subpetiolar process present. Postpetiole only a little wider than petiole and not much narrower than gastric segments I-IV, which are subequal among themselves in length and width; postpetiole separated from gaster by a distinct constriction. Pygidium bluntly rounded; hypopygium ending in paired, long posterior spines (fig. 117) and a short median tooth (in C. parallelusHNS). Genital capsule complete; parameres tend to be divided into basal and distal pieces (gonocoxites and gonostyli?); the capsule of C. parallelusHNS is shown in fig. 130.
Integument coarsely striate as in worker and queen, but the pterothorax (including pleura) are largely smooth and shining, with numerous, fine punctures; postpetiole variably sculptured; striate, longitudinally rugulose, or partly reticulate; gaster shining, very finely reticulate, and with scattered punctures.
Pilosity fine, short, predominantly decumbent. Color black, legs and antennae often prevailingly yellow or light brown.
Wheeler (1937: 443) already gave justification for synonymizing his own subgenus MetacylindromyrmexHNS, based on the 2 spurs on the hind tibiae; but these spurs are present on both middle and hind tibiae in all of the species I have seen. The subgenus HypocylindromyrmexHNS is distinguished by the small, flat eyes of the worker and the longitudinal striation of at least the basal part of the first gastric (IV true abdominal) tergum. It seems to me that this distinction is rather a weak one, deserving recognition at the species-group level at most. Furthermore, Wheeler's own C. darlingtoniHNS from Cuba has eyes of intermediate size, and these are slightly convex.
Another new group character needs to be considered: the metatarsus of the middle leg in the HypocylindromyrmexHNS workers and queens is very short and subtriangular, broadened rapidly from base to apex, and bears an apical circlet of 3 - 4 stout, conical spinelike setae, at least 2 of which are directed laterad. This metatarsus is only about twice as long as its greatest breadth, less than half the length of the whole tarsus of which it is a part, and also less than half the length of the metatarsus of the hind leg, which is itself rather short but still cylindrical. In C. striatusHNS and C. brasiliensisHNS, the middle metatarsus is slender and elongate, more than 4 times as long as broad, and similar in proportions to the considerably longer metatarsus of the hind leg. C. darlingtoniHNS, C. meinertiHNS, C. brevitarsusHNS and C. parallelusHNS all have the short middle metatarsus, but an intermediate condition holds in the queen of C. boliviaeHNS, for which the worker is still unknown. In this last species, the middle metatarsus is almost 3 times as long as its greatest (apical) breadth. So far as known in this genus, queens and workers are alike in appendage characters and it would be interesting to know if the worker of boliviaeHNS is intermediate in eye size as well as metatarsal proportions. In any case, known intermediates connect the extreme HypocylindromyrmexHNS to CylindromyrmexHNS for each of the 3 known " diagnostic " characters, and I do not think a formal division can be maintained.
bionomics: The species of CylindromyrmexHNS nest in cavities in sound or rotten wood, under bark, in hollow stems of standing or fallen plants such as the castor bean, and in similar situations. The small-eyed species are evidently more cryptic in habits than are large-eyed forms such as C. striatusHNS. The workers and even nests of several species have been found in termite galleries, and males and queens of C. parallelusHNS collected in a log on Barro Colorado Island, Panama Canal Zone, by A. E. Emerson, are pinned with workers and sexual forms of a termite in the MCZ. Consequently, the old assumption that the genus is termitotherous is probably correct. Still, it would be useful to have some detailed observations on the feeding habits.
distribution: New World tropics, from Central America to southeastern Brasil and Bolivia; Galapagos Islands.