Monomorium dentatum, Sharaf, M. R., 2007

Sharaf, M. R., 2007, Monomorium dentatum sp. n., a new ant species from Egypt (Hymenoptera: Formicidae) related to the fossulatum group., Zoology in the Middle East 41, pp. 93-98 : 94-97

Monomorium dentatum sp. n.

(Figs 1 & 2)

Holotype. Worker, Egypt, Damietta , 20.viii.2003, 31°26'N, 31°48'E, leg. M. R. Sharaf . - Paratypes: 17 workers, same series as holotype , 13 workers, Abu-Swelem, El-Minyia, 29.vi.2003, 28°06'N, 30°45'E, leg. M. R. Sharaf ; 3 workers, Abuzabal, Qalyubiya , 21.vi.2003, 30°03'N, 31°15'E, leg. M. R. Sharaf ; 1 worker, Port Said , 26.viii.2003, 31°16'N, 32°18'E, leg. M. R. Sharaf .

The holotype is deposited in the entomological collection of the Egyptian Entomological Society, Cairo (EESC); paratypes are deposited in the entomological collection of the Entomology Department, Faculty of Science, Ain Shams University, Cairo (ASUC) and in the entomological collection of the Ministry of Agriculture, Giza (MAC).

Measurements of workers [holotype in brackets], TL 1.49-1.63 [1.63]; HL 0.39-0.43 [0.41]; HW 0.33-0.36 [0.34]; CI 82.9-92.3 [82.9]; SL 0.34-0.35 [0.34]; SI 98.6-101.4 [100]; EL 0.02 [0.028]; PL 0.184-0.210 [0.184]; PW 0.110-0.120 [0.113]; PPL 0.110-0.127 [0.127]; PPW 0.09- 0.127 [0.127] (13 specimens measured including the holotype and the same series, Damietta , 20.viii.2003, 31°26'N, 31°48'E ).

Worker description. A unicolorous yellow, smooth, shining and slightly hairy ant. Monomorphic with very small size variation within the same nest. Head clearly longer than broad, smooth and shining with abundant, minute and scattered hair pits on the dorsum; sides of head with dense and relatively long yellow hairs. Mandibles armed with 4 teeth, the 3rd and the 4th teeth not close to each other; the whole mandible surface with relatively long and abundant yellow hairs. Frontal carinae very short; the area behind the lateral clypeal margins and adjacent to antennal insertions widely depressed. Antennae 12-segmented with a well defined 3-segmented club; antennal scapes with abundant and relatively long hairs; funiculus with very short and dense hairs; antennal club with very dense pubescence; the terminal funicular segment clearly longer than the two preceding segments together; the 2nd to 8th funicular segments clearly wider than long. Eyes very tiny with one ommatidium. Occiput raised. Pronotum sides smooth; promesonotum in profile with dorsal outline evenly convex; metanotal groove sharply defined as a U-shaped impression; junction of propodeal dorsum and declivity equipped with a pair of minute tubercles or tiny denticles; propodeal spiracles relatively large and round; lower part of mesopleuron faintly but conspicuously punctulateshagreenate; impression between mesopleuron and metapleuron faintly cross-ribbed. Pronotum with about 9 pairs of relatively long erect hairs; mesonotum with 3 pairs, propodeal dorsum with 2 pairs of hairs. Petiole pedunculate, with a high rounded node and one pair of long hairs; subpetiolar process simply dentiform. Postpetiole as long as broad, with one or two pairs of hairs. Gaster smooth and shining with abundant scattered and relatively long hairs. Dorsal surfaces of head, alitrunk and gaster unsculptured except for scattered hair-pits.

Remarks. This new species is a member of the Monomorium fossulatum-group as defined by Bolton (1987) and cannot be identified with any of the Monomorium species in Bolton's key to the Afrotropical species. M. dentatum appears taxonomically closest to M. sersalatum Bolton , 1987, which was described from Rwanda, and M. thrascoleptum Bolton , 1987, which was described from Ivory Coast. All three species are uniformly yellow; the promesonotum profile is evenly convex, the propodeum immediately behind the metanotal groove rises to an acute peak then slopes posteriorly to a pair of distinct projecting denticuliform angles at the junction of the dorsum and declivity; the propodeum with two or three pairs of hairs; the scapes and sides of the head behind the eyes have erect to suberect pubescence; sides of pronotum are smooth; and the area between the mesopleuron and metapleuron is faintly cross-ribbed.

M. dentatum may be closer to M. thrascoleptum , but is consistently smaller, TL 1-49-1.63 versus TL 1.9-2.2 mm; has a lower scape index, SI<100 versus SI 103-110; and M. dentatum also has sculpturation on the mesopleuron, which is smooth in M. thrascoleptum . The latter is known only from a single collection from Ivory Coast, West Africa.

Comparing M. dentatum with M. sersalatum , the scape index is similar but M. dentatum is smaller, TL 1.63 mm or less, versus TL 2.0-2.2 mm; the metanotal groove in M. dentatum is distinctly U-shaped whereas in M. sersalatum it has a sharply defined V-shape; in M. sersalatum the erect hairs on the body are shorter (Bolton 1987).

The Monomorium fossulatum-group contains seven species, widely distributed in tropical Africa (bolton 1987) and two species, M. fossulatum Emery and M. australicum Forel , which are widespread in the Indo-Australian region and on the islands of the Pacific and Indian Oceans (Wilson & Taylor 1967).

The new species has been collected from different localities in Egypt (Damietta, ElMinyia, Qalyubiya and Port Said) and represents the first record of the fossulatum-group from Egypt and the Palaearctic region. It seems likely that M. dentatum sp. n. has a wide distribution inside Egypt especially in the Nile river valley because specimens collected from Damietta, Abu-Swelem (El-Minyia) and Abuzabal (Qalyubiya) are all rather close to the river with the exception of the single specimen collected from Port Said.

Derivatio nominis. The species name is based on the dentate propodeum and was proposed by Cedric A. Collingwood.

Ecological observations. One type series, including the holotype, was found nesting under a rock in a small village 3 km from El-Minyia city (Upper Egypt); there were many Collembola and a single unidentified specimen of the ant genus Pyramica (Trichoscapa) Roger, 1862 , living in the same niche.