Key to Trichomyrmex

A worker key for the entire genus. This key was created by Ben Hoffmann (13 Jan, 2021).

The following key is my personal attempt at bringing together the Trichomyrmex species to assist species identification, especially for biosecurity purposes. It has been developed entirely from photos and information obtained from websites dedicated to ants by many people. I like to use simple language as much as possible. It is no-doubt imperfect, potentially lacking species, and characters I have used may not be consistent or reliable within the intraspecific morphological variation of the species. There may also be better characters to use for differentiation that I have missed. I welcome any feedback by anybody to modify this key (ben.hoffmann@csiro.au).

Please note that the key does not include Trichomyrmex bodenheimeri and Trichomyrmex rogeri. Trichomyrmex bodenheimeri was described by Menozzi in 1929. This ant is only known from the worker holotype and there are no images of this specimen. This specimen needs to be re-examined to understand how it compares to its congeners. The other species missing from this key, Trichomyrmex rogeri, is only known from the queen caste.

There are species and subspecies of Trichomyrmex
 * Species Checklist
 * Species by Country
 * Trichomyrmex Genus page

1

 * Cepahlic dorsum from the level of the eyes to the posterior margin entirely smooth and shiny without any punctation or striae apart from hair insertion points. At most some slight transverse striae on the occipital border . . . . . 2
 * Cepahlic dorsum from the level of the eyes to the posterior margin with punctation or striae in any amount . . . . . 20

2
return to couplet #1
 * Unicolorous yellow species. Dorsum of head smooth and shiny, at most with some striae on the occipital border. Occipital border deeply concave. Propodeal dorsum densely punctulate-reticulate without transverse reticulation. Eyes conspicuously large (EI 31-37) . . . . . 3
 * All features not as above . . . . . 5

3
return to couplet #2
 * Standing hairs on the mesosoma . . . . . 4
 * No standing hairs on the mesosoma . . . . . Trichomyrmex shakeri

4
return to couplet #3
 * Postpetiole longer than wide. Posterior margin of head distinctly narrower than the width of the clypeus. Scapes not reaching the central posterior margin of the head by approximately one third their length . . . . . Trichomyrmex nengraharicum
 * Postpetiole distinctly wider than long. Scapes only barely not reaching the central posterior margin of the head . . . . . Trichomyrmex santschii

5
return to couplet #2
 * Underside of head with numerous long J-shaped hairs forming a distinct psammophore . . . . . 6
 * Underside of head with no hairs, scattered short hairs or few long hairs but not forming a distinct psammophore (Fig. 1B) . . . . . 8

6
return to couplet #5
 * Unicolorous black species. Eyes reniform in profile, with distinctly concave ventral margin and broadly convex dorsal margin. Propodeal dorsum making an obtuse angle with propodeal declivity in profile. Posterior margin of head strongly concave in full-face view. Underside of head with abundant long ammochaete J-shaped hairs forming a distinct psammophore . . . . . Trichomyrmex almosayari


 * All features not as above . . . . . 7

7
return to couplet #6
 * Scapes reach the posterior margin of the head (SI 82). Posterior margin of head nearly straight or shallowly concave. Cephalic dorsum between frontal carinae and in front of eyes longitudinally rugulose with posterior half slightly shining. Area either side of the mid-dorsal strip of the head showing some fine longitudinal striolae both otherwise the posterior half of the head void of striae and punctations and being smooth and shiny. No transverse striae on the occipital border. Head and mesosome concolourous light orange . . . . . Trichomyrmex chobauti


 * Scapes not reaching the posterior margin of the head by a distance less than the maximum diameter of the scapes. Posterior margin of head shallowly concave. Entirety of cephalic dorsum with striae. Transverse striae on the occipital border. Entire body deep orange to dark brown . . . . . Trichomyrmex chobauti ajjer

8
return to couplet #5
 * Anterior clypeal margin with a pair of extremely well-developed teeth, far greater than any minor angles at the ends of a declivity in the anterior clypeal margin . . . . . 9
 * Anterior clypeal margin without well-developed teeth, or such projections are just minor angles . . . . . 10

9
return to couplet #8
 * Nodes of both waist segments distinctly wider than long. Entire dorsum of head smooth and shiny, without striae . . . . . Trichomyrmex evansi


 * Nodes of both waist segments not distinctly wider than long. Area between the eyes and the clypeal margin with striae. No erect hairs on the first gastric tergite . . . . . Trichomyrmex glaber

10
return to couplet #8
 * Mesosoma and abdomen with no standing hairs . . . . . Trichomyrmex aberrans


 * Mesosoma with standing hairs . . . . . 11

11

 * Entire body covered with numerous long standing hairs giving it a lightly woolly appearance . . . . . Trichomyrmex criniceps


 * Not as above . . . . . 12

12
return to couplet #11
 * Petiolar spiracle on the peduncle, anterior to the beginning of the rise of the petiolar node . . . . . 13
 * Petiolar spiracle in line with or posterior to the beginning of the rise of the petiolar node . . . . . 14

13
return to couplet #12
 * Promesonotum in profile distinctly convex. Propodeum, petiole and postpetiole irregularly rugulose. Eyes positioned anterior to the midline. Petiolar node smaller than normal and leaning posteriorly . . . . . Trichomyrmex abyssinicus


 * Promesonotum in profile more flattened than convex after rising sharply anteriorly. Propodeum sides, petiole and postpetiole finely punctate-reticulate. Eyes positioned approximately on the midline . . . . . Trichomyrmex perplexus

14
return to couplet #12
 * Head in full face view approximately square shaped, not distinctly longer than wide. Centre of eye at or extremely close to the midline . . . . . 15
 * Head in full face view longer than wide. Centre of eye distinctly anterior to the midline . . . . . 16

15
return to couplet #14
 * Longitudinal striae present posterior to the antennal insertions extending to between the eyes. Long petiole and postpetiole wider than long. Erect hairs not much longer than the length of the eye . . . . . Trichomyrmex muticus


 * Any longitudinal striae present posterior to the antennal insertions not extending to between the eyes. Promesonotum in profile strongly convex. Transverse sculpture of propodeal dorsum coarse and broadly spaced. Pilosity of mesosoma, petiole, postpetiole and gaster longer, and strongly curved, longer than 3x eye length . . . . . Trichomyrmex robustior

16
return to couplet #14
 * Head yellow, alitrunk dark brown, gaster yellow; the colours of the head and alitrunk strongly contrasting . . . . . Trichomyrmex epinotalis


 * Not as above . . . . . 17

17
return to couplet #16
 * Entire body light yellow. Eyes just anterior to the widest point of the head in full-face view . . . . . Trichomyrmex oscaris


 * Entire body colour not light yellow, often with greatly contrasting colour among body parts . . . . . 18

18
return to couplet #17
 * Eyes positioned approximately at the widest part of the head. Posterior of the head distinctly concave. Head only slightly longer than wide. Mesosoma and waist segments distinctly lighter in colour than the head and abdomen. Propodeal spiracle eliptiod, not spherical . . . . . Trichomyrmex dentigera


 * Eyes positioned well anterior to the widest part of the head. Posterior of the head only very weakly concave. Head distinctly longer than wide. Propodeal spiracle spherical . . . . . 19

19
return to couplet #18
 * Head and mesosoma yellow contrasting with black gaster . . . . . Trichomyrmex destructor


 * Head and mesosoma brown or reddish brown, near concolourous with the gaster . . . . . Trichomyrmex mayri

20
return to couplet #1
 * Dorsum of head entirely punctate without striae or regulation, at most only some obsolete striae at the anterior end. Scapes long, exceeding the occipital border. Clypeal margin distinctly convex . . . . . 21
 * Dorsum of head with some striae or regulation . . . . . 22

21
return to couplet #20
 * Mesosoma entirely punctate. Mesosoma profile very flat . . . . . Trichomyrmex wroughtoni
 * Mesosoma smooth, without any sculpture. Body devoid of pubescence and erect hairs . . . . . Trichomyrmex kempi

22
return to couplet #20
 * Cephalic dorsum opaque, shagreenate-granular to punctulate-shagreenate, with the mid-dorsal strip of the head showing extremely fine longitudinal scratch-like striolae. Entire body glabrous. Head longer than wide. Head, mesosoma, waist segments and first tergite concolourous yellow . . . . . Trichomyrmex dilatatum


 * Entire dorsum of head covered in coarse striae that are distinctly finely and densely longitudinally costulate. Head and mesosoma colour deep orange to dark brown . . . . . 23

23
return to couplet #22
 * Dorsum of head with short appressed hairs whose maximum length barely exceeds the width of the antennal scapes . . . . . Trichomyrmex lameerei and Trichomyrmex lameerei stauderi Note that there is currently no official photograph of the latter, and the striations on the Antweb photograph of T. lameerei better match those of the drawing of T. lameerei stauderi from the type manuscript. Note that the original drawings also show distinct differences in eye size, shape and position between these two “species”.


 * Dorsum of head with long appressed hairs whose maximum length greatly exceeds the width of the antennal scapes . . . . . 24

24
return to couplet #23
 * In dorsal view, petiole and the peduncle < twice as long as the post petiole . . . . . Trichomyrmex emeryi and Trichomyrmex emeryi laevior Note that there is no current official photograph of this latter species and the type description is in german.


 * In dorsal view, petiole and the peduncle more than twice as long as the post petiole . . . . . Trichomyrmex scabriceps