Tetramorium densopilosum Radchenko & Arakelian, 1990

Csősz, Sándor & Schulz, Andreas, 2010, A taxonomic review of the Palaearctic Tetramorium ferox species-complex (Hymenoptera, Formicidae), Zootaxa 2401, pp. 1-29 : 15-17

Tetramorium densopilosum Radchenko & Arakelian, 1990

Tetramorium densopilosus Radchenko & Arakelian, 1990: 372 . Holotype queen and paratype worker, male (6w, 4m): Armenia, Nature Reserve, 14.VI.1986 (A. Radchenko) [label: Arm SSR Khosrovskij, z-k No 237.86, A.Radchenko 14.6.86] (examined) [SIZK].

Description of workers (figs 25–27). Medium to large size, CS 833 [763, 878]. Whole body and appendages light brown to brown. Head slightly longer than broad, CL/CW 1.04 [1.02, 1.05], with straight sides, straight posterior head margin and rounded corners. Eyes small, EYE 0.17 [0.17, 0.18]. Frons moderately wide, FR/ CS 0.40 [0.38, 0.41], frontal lobes usually as wide as the frons, rarely slightly broader, FL/FR 1.00 [1.00, 1.02]. Scape long, SL/CS 0.78 [0.76, 0.80], with a feeble dorsal carina basally. Promesonotal dorsum slightly convex, metanotal groove moderately deep. Propodeal denticles moderately long. Petiolar node very high, NOH/NOL 1.23 [1.06, 1.44] trapezoid seen in profile, steeply rounded backward.

Head longitudinally rugulose and microreticulate, posterior surface ruguloso-reticulate, ground surface microreticulate, appears dull. Mesosoma dorsum and mesopleura ruguloso-reticulate, ground surface coarsely microreticulate. Dorsum of petiolar node ruguloso-reticulate, ground surface microreticulate, median part smooth. Dorsum of postpetiole rugulose and microreticulate. First gastral tergite smooth, appears shiny. Ventral surface of head with a row of short setae only (without long C-shape hairs).

Description of gynes (figs 22–24, 28). Medium to large size, CS 980 [970, 990]. Head, mesosoma and appendages light brown, gaster dark brown. Head broader than long, CL/CW 0.87 [0.83, 0.90] with sides and posterior margin straight. Head trapezoid in full face view, narrower at genae. Frons moderately wide, FR/CS 0.40 [0.38, 0.41]. Scape long, SL/CS 0.76 [0.74, 0.78], without a dorsal carina basally, its surface is smooth and shiny. Head slightly narrower than scutum, MW/CS 1.06 [1.05, 1.07]. Propodeal teeth long and acute. Petiole and postpetiole wide, CS/PEW 1.71 [1.68, 1.75], CS/PPW 1.28 [1.24, 1.33].

Head dorsum, posterior surface and sides ruguloso-reticulate, ground surface microreticulate. Frons longitudinally rugulose and microreticulate. Scutum and scutellum longitudinally rugulose. Sides of mesosoma, rugoso-reticulate and microreticulate, ventral part of katepisternum always rugulose, or microreticulate. Dorsum of petiolar node and postpetiole coarsely reticulate and microreticulate, medially shiny. First gastral tergite smooth, appears shiny, 1st gastral tergite very densely covered by pubescent hairs. Ventral surface of head with a row of short setae only (without long C-shape hairs).

Description of males. Head sides feebly convex, posterior margin and corners rounded. Scutum much broader than head. Propodeal denticles short but acute, propodeum angulate in profile. Dorsum of petiolar with a transverse crest, dorsolaterally sharp and angulate. Whole body and appendages brownish black. Head, scutum, scutellum, anepi- and katepisternum as well as petiole and postpetiole finely rugulo-reticulate, between main sculpturation microreticulate. First gastral tergite smooth, appears shiny, 1st gastral tergite very densely covered by pubescent hairs.

Diagnosis. The very dense pubescence on the first gastral tergite (Fig. 28) makes the T. densopilosum gynes unique within this group.

Tetramorium densopilosum workers cannot be confused with those of T. diomedeum or T. aegeum . The general appearance of the head and mesosoma of T. densopilosum workers is always rugulose and microreticulate, but head and mesosoma of the two latter species are always shiny and usually at least partly smooth.

FIGURES 22–28. Tetramorium densopilosum Radchenko & Arakelian, 1990 . Gyne mesosoma, petiole and postpetiole, dorsal view (Fig. 22), lateral view (Fig. 23); gyne head, dorsal view (Fig. 24); worker head, dorsal view (Fig. 25); worker mesosoma, petiole and postpetiole, dorsal view (Fig. 26), lateral view (Fig. 27); dense pubescence pilosity on 1st gastral tergite of a gyne (Fig. 28).

Tetramorium feroxoide workers usually bear feeble, often parallel rugulae on head and mesosoma. Discriminant function D(3a) = -0.1025 FL +0.0712 MW –0.0942 SPSP +8.1089 for T. densopilosum and T. feroxoide workers resulted in 100% success, and each case (56 individuals) was correctly identified. The mean D(3a) scores for T. densopilosum workers (n=8) was -2.191 ±0.89 [-3.512, -0.918], for nest means (n=2) -2.186 ±0.01 [-2.193, -2.180]. The mean scores for T. feroxoide workers (n=48) was 2.191 ±0.99 [+0.012, +3.911], for nest mean (n=2) -2.186 ±0.01 [-2.193, -2.180].

Separation of T. densopilosum and T. ferox workers is very difficult. With 8 observed workers we are not able to show variation in T. densopilosum . Tetramorium densopilosum workers have a slightly trapezoidal head and the petiolar node is slightly angulate anterordorsally (Fig. 26) in contrast to that of T. ferox , which is rounded. The frontal carinae are more developed in T. densopilosum , and also the erect hairs of mesosoma seem to be longer end denser than those of T. ferox . A discriminant D(4b) function proves the separation between T. ferox and T. densopilosum : see differential diagnosis of T. ferox .

For the results of cumulative discriminant analysis for worker caste see Tables 3 & 4 and for gynes see Tables 5 & 6 . Morphometric characters and indices for workers and gynes are provided in Table 7 & 8.

Distribution. This species is known from Armenia, Georgia and Eastern Turkey.

Material examined. GEORGIA—USSR, Georgia, Dranda, Kodori stream, 20.05.1975. leg. Zombori (1w / HNHM, 1w / PCAS); Georgia, USSR, Novy Afon, 24.05.1975, leg. Zombori (1w / HNHM);

TURKEY—Agri, Cilli Gecidi 30km N Dogubayazit 1600mH Strassenrand Steppe leg. Schulz, 30.06.1989 (2q / PCAS).