Monomorium pallidum Donisthorpe, 1918

Borowiec, Lech, Mossadegh, Mohammad Saeed, Salata, Sebastian, Mohammad, Shima, Torfi, Ebrahim Tamoli, Toosi, Mehdi & Almasi, Ali, 2019, Redescription of Monomorium pallidum Donisthorpe, 1918, revised status, Asian Myrmecology (e 011001) 11, pp. 1-7 : 3-6

Monomorium pallidum Donisthorpe, 1918 status revised ( Figs. 1-3 )

Monomorium (Paraholcomyrmex) destructor var. pallidus Donisthorpe, 1918: 166 .

Monomorium (Monomorium) pallidum : Crawley 1920: 178.

Monomorium (Paraholcomyrmex) destructor var. pallida : Emery 1922: 180.

Monomorium destructor pallida : Pisarski 1967: 48.

Monomorium pallidum : Borowiec 2014: 123.

Trichomyrmex destructor pallidus : Bolton 2018: AntCat.

Material examined

Type material: lectotype (here designated): Amara | Mesopotamia | ( Evans ) || pallidus Donis. || SYNTYPE || ex coll. | Donisthorpe. | B.M. 1934-4. || BMNHE | 1015255 || ANTWEB | CASENT0902219 ( BMNH) [examined]; all other syntypes from Amara preserved in BNMH have to be considered as paralectotypes.

Other material: 31 workers (19 in alcohol): IRAN, Khuzestan Prov. | Shoosthar | 11.v.2017 | Mossadegh ant group ( DBET, SCUA) ; 6 workers: IRAN, Khuzestan Prov. | Ahvaz-M.I.S., Hoda’ Park, 4.v.2017 | Mossadegh ant group ( DBET, SCUA) .

Description

Measurements: HL: 0.57 ± 0.02 (0.55-0.6), HW: 0.45 ± 0.01 (0.43-0.47), SL: 0.5 ± 0.02 (0.47- 0.53), EL: 0.11 ± 0.008 (0.1-0.12), EM: 0.13 ± 0.009 (0.11-0.14), ML: 0.68 ± 0.03 (0.63-0.72), PTL: 0.23 ± 0.01 (0.21-0.25), PPL: 0.15 ± 0.01 (0.14-0.17), PTH: 0.19 ± 0.007 (0.17-0.2), PPH: 0.17 ± 0.007 (0.16-0.18), PW: 0.29 ± 0.01 (0.27- 0.31), PTW: 0.14 ± 0.01 (0.12-0.16), PPW: 0.18 ± 0.009 (0.16-0.19), TL: 2.3 ± 0.06 (2.2-2.4), Indices: CI: 79.1 ± 1.7 (76.6-81.8), SI: 110.5 ± 4.0 (105.6-119.4), EI: 24.9 ± 1.6 (22.2-27.8) (n=10).

Head. In full-face view approximately 1.3 times longer than broad with shallowly convex sides and straight or shallowly concave posterior margin in full-face view; median clypeal portion without carina or anterolateral angles, anterior clypeal margin feebly concave; antenna 12-segmented; scapes moderately long, when laid straight back, reaching or slightly surpassing posterior margin of head, antennal club feebly but distinctly defined; mandibles armed with four teeth, decreasing in size from apex to base; eyes oval, moderate, placed distinctly in front of the midlength of head, with six to seven ommatidia in the longest row; frontal lobes farther apart in full-face view. Mesosoma. In lateral view with regularly convex promesonotal dorsum, which slopes posteriorly to a deep metanotal groove; propodeal spiracles small and circular; propodeal dorsum evenly sloping posteriorly to short declivity. Petiole. Node massive, narrowly rounded above, and as high as postpetiolar node in lateral view; anterior peduncle moderately long; ventral petiolar surface below node only slightly convex extending anteriorly to form a small dent; petiolar spiracle located in anterior sector of node. Postpetiole. Node large with convex dorsal margin; postpetiole slightly broader than high. Sculpture. Cephalic surface smooth and shining, only a few fine wrinkles curve posteriorly around the fossa; mandibles smooth and shining, sometimes with feeble longitudinal striation; pronotal dorsum smooth and shiny, sides with diffused striation and microreticulation but shiny; meso-and metapleuron finely microreticulate-punctate including dorsum of propodeum, without cross ribs; peduncle of petiole ventrally and dorsum of petiole and postpetiole with scattered microreticulation, appear shiny, sides of petiole and postpetiole distinctly shagreened but shining; gaster smooth and shining. Pilosity. Frontal part of head and posterior margin of head with four long erect hairs, anterior clypeal margin and mandibles with longer hairs, underside of head with numerous erect hairs only slightly shorter than hairs on front of head, pronotum with a pair of long hairs, mesoand metanotum without hairs only with sparse appressed pubescence; cephalic surface with scattered minute hair-pits; antennae with abundant appressed hairs; petiole and postpetiole with a pair of long hairs; gaster with numerous longer hairs on the first tergite, appressed pubescence absent. Color. Uniform clear yellow, in most specimens first gastral tergite apically with a pair of small brown patches of diffused borders, mandibular teeth brown.

DISTRIBUTION

Iraq (Baghdad and Majsan Provinces), Iran (Khuzestan Province), Israel & Palestine ( Jordan Valley and southern Golan, Central Coastal Plain, Southern Coastal Plain and Golan Heights regions). Recorded also from Afghanistan (Kandahar Province), but based on the description provided by Pisarski (1967) this record refers to different species. The species is a new record to Iran.

COMPARATIVE NOTES

Based on general morphology M. pallidum have most of the characters of the M. monomorium group as defined by Bolton (1987) and Sharaf et al. (2018): monomorphic, with size variation but without allometric variation; median clypeal portion raised, projecting anteriorly and longitudinally bicarinate; anterior clypeal margin without a pair of teeth; dorsal surface of mandibles unsculptured and masticatory margin armed with four distinct teeth, decreasing in size from apex to base; antennae with 12 segments, terminating in a well-defined three-segmented club; eyes present, situated in front of the midlength of the sides in full-face view, with more than four ommatidia in the longest row; head longer than broad; cephalic dorsum smooth and shining; metanotal groove impressed; propodeal spiracle circular; propodeal dorsum meeting declivity in a rounded angle; promesonotum and propodeal dorsum unsculptured; head, pronotum and first gastral tergite with erect hair; petiole and postpetiole partly and gastral tergites completely unsculptured.

However, M. pallidum can be distinguished from other members of the M. monomorium species-group in metanotal groove lacking cross-ribs and finely sculptured propodeal dorsum. The latter feature is also characteristic for Monomorium sarawatense , species included in the revision of the M. monomorium species-group ( Sharaf et al. 2018). Also, similar to M. sarawatense , M. pallidum has head with fine sculpture surrounding fossa. It can indicate that those taxa are closely related and create a separate unit within the M. monomorium group.

There are six species of the M. monomorium species-group known from Arabian Peninsula ( Sharaf et al. 2018). Four of them, M. aeyade Collingwood & Agosti , M. clavicorne André , M. exiguum Forel and M. mohammedi Sharaf & Hita Garcia differ from M. holothir Bolton, M. sarawatense Sharaf & Aldawood and M. pallidum in 11-segmented antennae. Among three species with 12- segmented antennae M. sarawatense differs in clubbed body setae, while M. holothir and M. pallidum have simple body setae. Monomorium holothir differs in dorsum of mesosoma with numerous erect setae and petiole and postpetiole completely smooth and shining while M. pallidum has only a pair of erect setae on pronotum and sides of petiole and postpetiole with reticulate microsculpture. Both, M. holothir and M. sarawatense , have gaster uniformly yellow to yellowish-brown, while in M. pallidum in most specimens occur brown spots in apical part of first gastral tergite.

The discussed characters for Monomorium pallidum indicate that perhaps the redescription of this taxon given by Pisarski (1967) concerns another species. He noted this taxon as uniformly yellow while lectotype and all recently studied specimens have distinct brown spot on each side of first gastral tergite.

In the key to the Arabian M. monomorium group proposed by Sharaf et al. (2018) M. pallidum runs to couplet 2 and the key is modified as follow:

2. Body pilosity clubbed; mesosoma, petiole and postpetiole distinctly sculptured (Fig. 4A in Sharaf et al. 2018) ................................................ .................... M. sarawatense Sharaf & Aldawood

-. Body pilosity simple; mesosoma, petiole and postpetiole smooth and shining (Fig. 4B in Sharaf et al. 2018) or with reticulate-punctate sculpture on their sides ( Figs. 1-2 ) ................................... 3.

3. First gastral tergite uniformly yellow to yellow-brown, dorsum of mesosoma with numerous erect setae, petiole and postpetiole completely smooth and shining (Fig. 8 in Sharaf et al. 2018) ................................................ M. holothir Bolton

-. First gastral tergite with brown spots on its posterolateral part, dorsum of mesosoma with two erect setae on pronotum, sides of petiole and postpetiole with reticulate-punctate microsculpture ( Figs. 1-2 ) ............. M. pallidum Donisthorpe

Figures

Figs 1 – 2. Monomorium pallidum Donisthorpe worker (scale bar – 0.5 mm). Fig. 1 – body in dorsal view, Fig. 2 – body in lateral view.

Fig. 3. Monomorium pallidum Donisthorpe worker (scale bar – 0.25 mm), head in full-face view.