Pristomyrmex punctatus

Aiki Yamada & Katsuyuki Eguchi, 2016, Description of the male genitalia of Pristomyrmex punctatus (Smith, 1860) (Hymenoptera, Formicidae, Myrmicinae), Asian Myrmecology 8 (1), pp. 1-8 : 4-7

MALE GENITALIA OF PRISTOMYRMEX PUNCTATUS

Description

Pygostyle digitiform with 3-8 long setae in its apical third ( Fig. 2 ). Abdominal sternite IX subhexagonal in outline ( Fig. 3 ); spiculum (anterior apophysis of the sternite IX, Sp in Fig. 3 ) short; anterior margins meeting in an obtuse angle basal to the spiculum; anterolateral sternal corners weakly produced anterolaterally; lateral margins slightly concave; posterolateral sternal corners somewhat produced anterolaterally; posteromedian part ventrally with long setae. Genital capsule longer than wide. Cupula wider than long, weakly constricted anteriorly ( Fig. 4 ), with its mesoventral part shortened anteroposteriorly as a transverse bridge (the anterior and posterior margins of cupula indicated by black dashed line in Fig. 4 ). Telomere distinctly differentiated from basimere by ventral notch (the notch indicated by dashed line in Fig. 5 ); oblique carina present on lower of basimere (BmC in Fig. 5 ); gonostipital arm (median anteroventral extension of the basimere indicated by red dashed line in Fig. 4 and Ga in Fig. 4 and 5 ) in ventral view almost as long as basal width, with its lateral and mesal margins converging and forming an acute apex; telomere in lateral view almost as long as high, with setae on the outer surface of its posterior part ( Fig. 6 ); ventral ridge of volsella with setae ( Fig. 5 ); cuspis in lateral view roundly lobate and short, not reaching posterior margin of digitus ( Fig. 7 ); digitus in lateral view claw-shaped, entirely hooked ventrad ( Fig. 7 ); very short setae with distinct sockets scattered ventrally on digitus. Valviceps in lateral view with posterior apex hooked ventrad, anteroventral corner not produced; ventral margin with 9–13 denticles ( Fig. 8 ); foveae (recognized as tunnels running inside valviceps) sparsely present on apical and ventral area of valviceps (some of apical foveae probably with short setae but obscure in optical microscope observation); valvura directed dorsoanterolaterally (Va in Fig. 9 ); lateral apodeme produced ventrolaterally (Lp in Fig. 9 ), forming wing-like structure which hold basal part of volsella in genital complex; penisvalva membrane densely spinate (Pvm in Fig. 9 ).

Remarks

General constitution of formicid male genitalia as shown by previous authors ( Krafchick 1959; Ogata 1987; Ogata 1991) was preserved in irregularly produced males of Pristomyrmex punctatus , and conspicuous deletion, deformation, or ornamentation of the main components was not recognized. Gonostipital arm which was claimed as a synapomorphy of the Myrmicinae by Ogata (1991) is present in the male genitalia of Pristomyrmex punctatus . But this structure is not a synapomorphy of the Myrmicinae because of its presence in other ant subfamilies and in other hymenopteran lineages ( Schulmeister 2003; Boudinot 2013). Based on a comparison of the male genitalia of P. punctatus with those of other myrmicine genera described and illustrated by Ogata (1991), the general features of male genitalia of Myrmicinae can be summarized as follows: (1) cupula wider than long; (2) gonostipital arm present, but variable in shape; (3) digitus strongly curved ventrad (except for Solenopsis japonica : both of digitus and cuspis reduced); (4) cuspis simple and reduced, shorter than digitus and nev- er protruding dorsad above digitus in lateral view, or absent. In order to understand morphological synapomorphies of Myrmicinae in male genitalia, more detailed and comprehensive comparision across taxa is needed.

In agreement with previous observations by Itow et al. (1984), the male genitalia of P. punctatus seem to be functional. Further comparison of the male genitalia between P. punctatus and amphigonic sister species, e.g., members of P. punctatus group (sensu Wang 2003), might provide valuable information for our better understanding of the origin of parthenogenesis in the genus.

Figures

Fig. 4. Entire genital capsule, dorsal view, dashed line indicates outline of ventral surface of cupula (black line) and anteroventral outline of basimere (red line). Scale bars = 0.1 mm. Cs cuspis; Cu cupula; Dg digitus; Ga gonostipital arm; Pm paramere; Pv penisvalva.

Figs 2 – 3. Pygostyle and abdominal sternite IX: (2) pygostyle, left side, dorsal view; (3) abdominal sternite IX, ventral view. Scale bars = 0.1 mm. Abbreviations: Sp spiculum.

Figs 5 – 7. Paramere and volsella. (5) paramere and volsella, right side, inner view; (6) anterior part of paramere, right side, inner view; (7) volsella separated from paramere, right side, inner view. Scale bars = 0.1 mm. Bm basimere; BmC carina of lower basimere; Cs cuspis; Dg digitus; Ga gonostipital arm; Tm telomere; Vo volsella.

Figs 8 – 9. Penisvalva. (8) penisvalva, left side, outer view. (9) pair of penisvalvae, dorsal view. Scale bars = 0.1 mm. Lp lateral apodeme of penisvalva; Pvm penisvalva membrane; Va valvura.