Friday, July 1, 2011

Identification and Distribution of Aphaenogaster

Aphaenogaster is a common genus of specialized scavengers. There are 27 accepted species in North America and many more to be discovered. The hardest to identify to species level are those in the "fulva, rudis, texana complex." A. fulva and A. rudis are more than likely several species nearly indistinguishable. A. texana thankfully looks different but branches off into numerous subspecies and varieties. From here we move on to more unique species and end with certain oddities I'm still working out. Hopefully this is helpful to someone out there.

Overall Aphaenogaster nest in the ground and occasionally have mixed nest or live directly in rotting wood.

Aphaenogaster fulva, rudis, and texana complex (I haven't been able to look at a study about this yet so some of these are differences I've noticed.)
Aphaenogaster fulva  (2)                               SC, SE, NC, NE
Spine length varies as does the angle and thus other than having spines can't be used for a good ID. The legs are a similar color to the body. Antenna scape are fairly short. Mesonotum is abruptly raised above the pronotum, fallowed by a depression. The katepitemum (from side view part of thorax that connects to the middle leg's coxa,) is fairly fat looking compared to A. rudis, A picea, and especially A. texana. The head is a slightly longer oval shaped compared to the other 3 species.

Aphaenogaster rudis (2)                                 SC, SE, NC, NE, Eastern Canada
Brown in color. Often the ant is bicolor with brown-red, brown, and black. Legs are usually lighter in color as well. The katepitemum is between that of A. fulva and A. texana in terms of girth. The head is similar in shape to A. fulva but seems slightly flatter when looked at from the side view. 

Aphaenogaster picea (2)                              SE, NC, NE, Eastern Canada
Darker in color, usually black. Legs are usually lighter than the body. The katepitemum is between that of A. fulva and A. texana. Head is rounder looking than A. fulva from a side view.

Aphaenogaster texana                               SW, SC, SE, NC, NE
Body color is brownish red. Legs are usually lighter than the body. The katepitemum is very slim and thin looking. The head is also much slimmer looking than any other species in the complex. Eyes are also larger.
There is some dispute over how big the queen is. One study suggested queens are 8 to 8.5mm. Another proudly said they're 11mm long. One study mentions A. texana var. furvescens which isn't an official species as far as I can tell, and says their queens are 7.5mm. Workers to var. furvescens are said to be redish brown in color with a dark brown abdomen except for the tip. True texana in face view has a flat head up top.

Aphaenogaster texana var. miamiana                           SE (Florida)
Pubescence on legs is thicker than true A. texana. Spines are slightly longer too. Body color is red with a darker abdomen and lighter colored legs and antennae. The head is rounded at the top but only slightly.

Aphaenogaster texana var. carolinensis                         SE (Georgia)
On average slightly smaller than true A. texana. Spines are less erect and point more towards the abdomen. Underside of the head, thorax, waist segments, and abdomen varying from light and dark brown. In face view the head is rounded at the top.

Aphaenogaster texana var. flemingi                              SE (Florida)
Hair is longer than true A. texana.  Spines are much longer too. In face view the head is rounded at the top.

Aphaenogaster texana var. huachucana                        SW
Found around 7000ft nesting under stones on a rocky slope. Mesonotum and propodeum are divided by a "U" shaped depression (open side facing the propodeum). Color is red-brown to yellow brown. Legs are either yellow-brown too or yellow. Hair is few and far between compared to other Aphaenogaster.

Aphaenogaster texana var. punctaticeps                       SW, SC
Fair amount of long hairs sparsely distributed on the body. The head is rounded at the top. Similar to A. huachucana but the scape is fatter at the base.


Standard Aphaenogaster
Aphaenogaster megommata                       SW, NW
This ant is common species that forages at night. Nuptial flights are also held during this time. Nests are found in soil but hard to spot from the lack of any mound or craters around the entrance. This ant has huge eyes compared to the head. The color is also distinct and described as "callow-like" as though it never fully gained the pigment after the pupa stage. One could also say it's a very pail yellow with light brown. Spines are underdeveloped looking and the word tubercles is more appropriate.

Aphaenogaster tennesseensis (2)                    SC, SE, NC, NE, Eastern Canada (social parasite to A. fulva)
Spines are very long with a slight curve. The head thorax and most of the legs are a robust red color. The abdomen, coxa, and waist segments are a light orange color. Very few erect hairs on the body. Pubescence is sparse too except on the antennae. Queens are social parasites to A. fulva species.

Aphaenogaster cockerelli (2) (3)                      SW, SC, Mexico
Fairly large at around 8mm long. Color ranges from red to dark brown to almost black. Hair also ranges from long to moderate in length about the body. The dorsum of the thorax is smoothly curved with a flat mesonotum. Spines are long and curved. The eye is somewhat big compared to the head too but not as big as A. megommata.  

Aphaenogaster albisetosa (2)                          SW
Similar to A. cockerelli but hairs are more abundant.

Aphaenogaster ashmeadi                            SE
(still working on)

Aphaenogaster lamellidens                         SE, NE
In the southern part of it's range legs typically contrast from dark brown to lighter on the tibia and femur. Spines are fairly long. "Distinctly has a tooth like lobe on the frontal carina that points towards the head behind it." (...I have no idea what that means.)

Aphaenogaster mariae (2)                              SC, SE, NC, NE
Body is very textured and Myrmica-like; looking similar to the skin of rotting fruit. The abdomen is smooth and shiny. Hair is sparse overall but abundant on the head, abdomen, legs, and antennae.

Aphaenogaster subterranea                        SW, Western Canada (odd distribution)
Hairs are sparce on the thorax but abundant on the legs, head and antennae. The abdomen is mostly free of hair. The pronotum and mesonotum are together convex almost perfectly.

Aphaenogaster treatae  (2)                          SE, SC, NE, NC
Easily identified by a distinctive lobe at the base of the antenna, appearing as a thick somewhat flattened patch. 

Aphaenogaster umphreyi                           SE (Florida)
The body is very textured except for the abdomen. Brown-red in color with lighter legs. Hair is abundant around the body.

Aphaenogaster boulderensis                        SW, NW
Hairs are moderately long and sparse on the body, with shorter hairs on the antennae, tibia, and tarsi. The body color is usually a light yellowish brown with darker mandables, parts of the head, legs, antennae, and of course the abdomen which is normally black.

Aphaenogaster floridana                             SE (Florida)
Suberect hairs are sparse on the body. Shorter hairs on the antennae, and legs are hard to notice. Spines are underdeveloped looking and the word tubercles is more appropriate.

Aphaenogaster mutica                               NW, Mexico?
Very average looking, besides a shaggy amount of hair on the legs and antennae. A fair amount on the abdomen, and head, with fairly little on the thorax. The body color is reddish with paler yellows. The abdomen is darker. Spines are underdeveloped looking and the word tubercles is more appropriate.

Aphaenogaster uinta                                  SW, NW
4.5 to 5mm long. The head and thorax are a yellow-red color (orange?) with the abdomen as black. Legs are lighter in color often yellow. Queens measure 7mm long and are colored similarly. Spines are underdeveloped looking and the word tubercles is more appropriate.

Some Oddities
Aphaenogaster mexicana                           Mexico
Originally described as an Ischnomyrmex species. This ant is about 7mm long. The head thins out forming a collar around the neck area before the thorax starts. Spines are underdeveloped looking and the word tubercles might be more appropriate.

Aphaenogaster occidentalis (2)                       SW, NW, (NC Nebraska)
(still working on)

Aphaenogaster patruelis                             SW (California)
(still working on)

Aphaenogaster patruelis carbonaria             SW (California)
(still working on)
Sources
Smith, M. R. 1941. Two new species of Aphaenogaster (Hymenoptera: Formicidae). Great Basin Naturalist 2: 118-121.
Smith, M. R. 1928. An additional annotated list of the ants of Mississippi. With a description of a new species of Aphaenogaster (Hym.: Formicidae). Entomological News 39: 275-279.

Creighton, W. S. 1934. Descriptions of three new North American ants with certain ecological observations on previously described forms. Psyche 41: 185-200.

Smith, M. R. 1963. A new species of Aphaenogaster (Attomyrma) from the western United States. Journal of the New York Entomological Society 71: 244-246.

Pergande, T. 1896. Mexican Formicidae. Proceedings of the California Academy of Sciences (2)5: 858-896

Mackay, W. P. 1989. A new Aphaenogaster (Hymenoptera: Formicidae) from southern New Mexico. Journal of the New York Entomological Society 97: 47-49.

Wheeler, W. M. 1915. Some additions to the North American ant fauna. Bulletin of the American Museum of Natural History 34: 389-421.

Wheeler, W. M. 1917. The mountain ants of western North America. Proceedings of the American Academy of Arts & Sciences 52: 457-569.

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