Sphaeropthalma imperialis

Pitts, James P., 2006, Review of the Sphaeropthalma imperialis species­group (Hymenoptera: Mutillidae), with descriptions of females and taxonomic notes, Zootaxa 1248, pp. 1-20 : 4-6

Sphaeropthalma imperialis species­group

Diagnosis

Males have the head rounded to quadrate posteriorly ( Figs. 1, 2 ). The mandibles are broadly dilated and vertical throughout with the dorsal carina sharp and complete to the dorsal (third) mandibular tooth ( Figs. 5–7 ). The mandible also has only a slight angulation on the ventral margin ( Figs. 5–7 ). The clypeus varies from slightly to deeply depressed forming a basin with the closed mandibles. The mesosternum, coxae and trochanters are unarmed. The marginal cell is acuminate to almost truncate distally. Notauli are complete and deep. Parapsidal furrows are present on posterior portion of mesonotal disk. The sternal felt line is either entirely absent or present as small but distinct tuft. Genitalia are distinct for the species­group, having a long cylindrical cuspidis bearing simple setae ( Figs. 8–19 ). Females have the head round and not as wide as the mesosoma. The eyes are round and the antennal scrobes are carinate dorsally. The mesosoma varies from slightly longer than wide to distinctly wider than long. The first metasomal segment is distinctly petiolate with the second segment. The pygidium is defined laterally by carinae and is colliculate to distinctly granulate in sculpture ( Fig. 23 ). The females also bear plumose and brachyplumose setae.

Remarks

Study of Schuster’s S. imperialis species­group revealed that the marginal cell of S. imperialis and S. imperialiformis are similar to that of the S. edwardsii species­group sensu Schuster and are never as short, or shorter, than the stigma as stated by Schuster (1958). Furthermore, after surveying all of the characters used by Schuster to separate the males of the S. edwardsii species­group from those of the S. imperialis species­group, these two species­groups differ only by presence or absence of a sternal felt line. This level of variation in the development of the sternal felt line occurs in other Sphaeropthalma species­groups and in the small genus Dilophotopsis Schuster. Study of the genitalia, which was not considered by Schuster, has revealed that they are quite similar in morphology as well, but differ from other Sphaeropthalma species­groups. As such, these four species are deemed closely related and the S. imperialis species­group is redefined to contain S. edwardsii , S. imperialis , S. marpesia , and S. megagnathos .

Mandibular morphology of the males of the S. imperialis species­group is quite similar to that of the S. pensylvanica species­group. These two Sphaeropthalma species­groups also share integumental melanization, or at least integumental coloration darker than the normal “nocturnal” brown seen in the remainder of the Nearctic Sphaeropthalma species. Be aware that the integumental coloration of S. megagnathos does, however, tend toward the standard light brown coloration normal for other Sphaeropthalma species. The genitalia, especially the shape and vestiture of the cuspidis and the shape of the parameres, differ greatly between these two Sphaeropthalma species­groups (see Pitts 2005). Other Sphaeropthalma species in Central and South America, which are mostly undescribed, and S. unicolor (Cresson) found in the Western USA can also have brown to black integumental coloration, but these species have a different mandibular morphology with the apex oblique rather than vertical and greatly differing genitalic morphology.

The mandibular morphology of the males of the S. imperialis species­group also is similar to that of the Odontophotopsis venusta and, to a lesser extent, the O. conifera , O. parva and O. tapajos species­groups. These groups, however, can be easily separated from the S. imperialis species­group due to generic­level characters alone.

The females of this species­group are defined by the small ventral angulation located basally on the mandible, the distinctly petiolate metasomal segment 1, the granulate pygidium, which is defined laterally by carinae, and presence of plumose setae especially on the fringes of the metasomal tergites. These females are morphologically similar to Dilophotopsis concolor crassa (Viereck) (being described elsewhere), Dilophotopsis stenognatha Schuster (see Mickel 1963), and S. orestes (Fox) (see Mickel 1938), especially the sculpturing of the pygidium. The ventral mandibular tooth is much smaller for the females of the S. imperialis group, however. These females differ from those of Stethophotopsis Pitts, the Sphaeropthalma uro species­group, and S. jacala Schuster by laterally defined pygidium (see Pitts & McHugh, 1999; Pitts & Manley, 2002; Pitts et al. 2004; Pitts & Parker, 2005). Manley and Pitts (2002) present other characters useful for diagnosing the females of Dilophotopsis , Sphaeropthalma and Stethophotopsis.

Distribution

Found throughout the western USA and northern Mexico.

Figures

FIGURES 1 – 7. 1. Sphaeropthalma imperialis male, posterior portion of head in dorsal view; 2 – 4. S. marpesia: 2. male, posterior portion of head, dorsal view; 3. female mesosoma, dorsal view; 4. posterior portion of second metasomal tergite; 5. S. imperialis male, mandible, lateral view; 6. S. marpesia male, mandible, lateral view; 7. 5. S. megagnathos male, mandible, lateral view.

FIGURES 8 – 19. Genitalia: penial valve, lateral view; internal lateral view, penial valve removed; ventral view left, dorsal view right; Sphaeropthalma edwardsii: 8 – 10. S. imperialis: 11 – 13. S. marpesia: 14 – 16; S. megagnathos: 17 – 19.

FIGURES 20 – 25. Sphaeropthalma imperialis female, dark form: 20. lateral view; 21. anterior portion of second metasomal tergite; S. imperialis female, light form: 22. lateral view; 23. pygidium, dorsal view; 24. S. edwardsii female, lateral view; 25. S. marpesia female, lateral view.