Key to Pheidole pilifera group

This worker key is based on:

The principal distinguishing feature of this almost exclusively Nearctic assemblage is the possession by the major caste of 0-3 hypostomal teeth, instead of the usual (but not invariable) 4-5 found in other species groups. To this may be added the typically quadrate head shape of both major and minor, as well as their short scapes. Furthermore, the minor of most of the species has proportionally large eyes (the ratio of Eye Length to Head Length among the species ranges from 0.14 to 0.40, with the majority falling 0.20- 0.25, well above the average for other groups). All together these traits allow pilifera-group species to be separated at a glance from unrelated species that also possess 2 or 3 hypostomal teeth, including some members of the Neotropical biconstricta group; Pheidole eidmanni, Pheidole gigas, Pheidole laevivertex, and Pheidole puttemansi of the fallax group: Pheidole nebulosa, Pheidole oaxacana, and Pheidole scabriventris of the flavens group; Pheidole capillata and Pheidole gertrudae of the gertrudae group; Pheidole clydei of the granulata group; and Pheidole fabricator, Pheidole pidax, and Pheidole polita of the tristis group; as well as the African tramp species Pheidole megacephala. The pilifera-group species are otherwise most similar in the totality of their major and minor traits to members of the flavens group.

You may also be interested in


 * Pheidole
 * "New World Pheidole" Wilson 2003

1

 * Major: occiput covered partly or entirely by carinulae, rugulae, or a rugoreticulum . . . . . 2


 * Major: occiput smooth and shiny, or sparsely foveate, or densely foveolate, but not bearing carinulae, rugulae, or a rugoreticulum . . . . . 24

2
return to couplet #1
 * Major: rear of head phragmotic, i.e ., occiput strongly concave and rugoreticulate, creating an armored surface (Sinaloa, Mexico) . . . . . Pheidole setsukoae


 * Major: rear of head not phragmotic; occiput convex and variously sculptured . . . . . 3

3
return to couplet #2
 * Major: all or almost all of the dorsal surface of the head carinulate, rugose, foveolate, or combinations thereof . . . . . 4


 * Major: a large portion of the dorsal surface of the head just anterior to the occiput, and including at least a third of the head capsule, smooth and shiny . . . . . 15

4
return to couplet #3
 * A trimorphic species, with heads of both the major and supermajor, including occiput, completely covered with parallel longitudinal carinulae. Very large (Head Width of major 2.5 mm, of supermajor 3.9 mm, and of minor 0.9 mm). Major and minor: propodeal spine in side view exceeding three-fourths the length of the basal face of the propodeum anterior to it (southern Arizona, northern Mexico) . . . . . Pheidole rhea


 * Major: dimorphic, or, if trimorphic, dorsum of head of major partly bare (part of frontal lobes and area behind frontal lobes in hirtula and obtusospinosa, most of posterior half of head dorsum in tepicana, and clypeus in all three species); smaller than rhea, with Head Width of major 1.0-1.6 mm and of minor 0.5-0.6 mm. Major and minor: propodeal spine in' side view only half the length of the basal face of the propodeum anterior to it . . . . . 5

5
return to couplet #4
 * Major: in side view head "dented"-its profile strongly concave just anterior to the occipital border (southern Texas) . . . . . Pheidole hoplitica


 * Major: in side view, profile smoothly convex, or straight, or at most very weakly concave just anterior to the occipital border . . . . . 6

6
return to couplet #5
 * Major: occiput completely and coarsely rugoreticulate. Minor: posterior half of dorsum of head completely covered by carinulae (Arizona) . . . . . Pheidole cavigenis


 * Major: occiput transversely carinulate or rugulose, lacking rugoreticulum. Minor: posterior half of head foveolate or smooth, not carinulate . . . . . 7

7
return to couplet #6
 * Major: most of the side of the head mesad and posterior to the eye all the way to the occiput is rugoreticulate . . . . . 8


 * Major: side of head mesad and posterior to the eye is smooth or longitudinally carinulate . . . . . 9

8
return to couplet #7
 * Major: smaller (Head Width about 0.90 mm) but with larger eyes (Eye Length about 0.18 mm); medium yellow (some populations of californica, a widespread species of the western U. S.) . . . . . Pheidole californica (in part - also )


 * Major: larger (Head Width about 1.10 mm) but with smaller eyes (Eye Length about 0.14 mm); dark yellow (San Clemente Island, mainland California, and Baja California) . . . . . Pheidole clementensis

9
return to couplet #7
 * A trimorphic species. Major: all of rear half of dorsal surface of head except occiput smooth and shiny. Supermaj or: all of rear half of dorsal surface of head carinulate and rugulose. Minor: lower half of mesopleuron and most of the side of propodeum smooth and shiny (Texas and Arizona to central Mexico) . . . . . Pheidole tepicana (in part - also )


 * Dimorphic or trimorphic species. Major: rear half of dorsal surface of head carinulate or rugulose (in supermajor, if present, most of rear half of dorsal surface lacks carinulae or rugulae) . . . . . 10

10
return to couplet #9
 * Major: sides of head posterior to and laterad to the eye mostly or entirely smooth and shiny. Minor: head and pronotum entirely foveolate and opaque . . . . . 11


 * Major: sides of head posterior and laterad to eye foveolate and opaque, or longitudinally carinulate, or both. Minor: head and pronotum entirely smooth and shiny . . . . . 12

11
return to couplet #10
 * Major: in side view, mesonotal convexity well developed, with a front face and descending to metanotal groove in a smooth curve; center of metanotum foveolate and opaque, with irregular, broken carinulae. Minor: longitudinal carinulae present laterad to eye (eastern U. S. populations of pilifera) . . . . . Pheidole pilifera (in part - also )


 * Major: in side view, mesonotal convexity absent; the promesonotum as a whole presents a continuous profile that descends to the metanotal groove in a steep posterior face. Minor: carinulae absent laterad to the eye (Chihuahua, Mexico) . . . . . Pheidole torosa

12
return to couplet #10
 * Trimorphic species, with occiput of major longitudinally carinulate . . . . . 13


 * Dimorphic species, with occiput of major transversely carinulate . . . . . 14

13
return to couplet #12
 * Occiput of supermajor in full-face view sparsely covered by round foveae, with interspaces smooth and shiny (upland central Mexico) . . . . . Pheidole hirtula (in part - also ))


 * Occiput of supermajor in full-face view sparsely covered by elongate foveae, with interspaces densely foveolate and opaque (montane southern Arizona, western Mexico) . . . . . Pheidole obtusospinosa (in part - also )

14
return to couplet #12
 * Major: center of promesonotal dorsum smooth and shiny. Minor: hairs on dorsa of mesosoma and petiole ordinary, not clavate. Major and minor: yellow (Arizona, southern California) . . . . . Pheidole micula


 * Major: center of promesonotum foveolate and opaque. Minor: most of the hairs on the dorsa of mesosoma clavate. Major and minor: light brown (Mississippi to southwestern U. S. and northern Mexico) . . . . . Pheidole soritis

15
return to couplet #3
 * Major: all of side of pronotum and upper half of sides of mesopleuron and propodeum covered by longitudinal carinulae; summit of petiolar node in side view acuteangular; seen from above, petiolar node drawn laterally into sharp points. Minor: posterior half of head carinulate (Colorado, New Mexico, Arizona) . . . . . Pheidole senex


 * Major: areas of body listed above lacking carinulae; summit of petiolar node in side view rounded; seen from above, the sides of the petiolar node either rounded or angular. Minor: posterior half of head not carinulate . . . . . 16

16
return to couplet #15
 * Major and minor: promesonotal profile seen from dorsal-oblique view (mesosoma rotated around long axis for 45 degrees from top view), with 3 convexities, 2 pronotal and a single mesonotal one, with the central convexity (second pronotal) being by far the highest. Minor: in full-face view, the occipital margin deeply concave, the two halves meeting to form an angle at midline; the eye enormous, as long as the entire petiole (Baja California Sur) . . . . . Pheidole bajaensis


 * Major and minor: promesonotal profile seen from dorsal-oblique view, with one or 2 convexities, or if 3, the central convexity is only about as high as the first convexity. Minor: in full face view the occipital margin variable, usually only shallowly concave and not forming an angle at midline; eye shorter than petiole . . . . . 17