Trypoxylon scrobiferum, Richards Supraantenal, 1934

Amarante, Sérvio Túlio P., 2005, On The Systematics Of Trypoxylon scrobiferum Richards and T. anapaike Amarante With The Recognition Of A New Species Group In The Subgenus Trypoxylon (Hymenoptera: Crabronidae: Trypoxylini), Papéis Avulsos de Zoologia 45 (9), pp. 91-101 : 96-97

The scrobiferum species group

The proper placement of T. scrobiferum and T. anapaike into the currently recognized and species groups of Trypoxylon is puzzling. They have character conditions that has been regarded exclusive either of Trypoxylon s.s. or of Trypargilum . Originally, Richards (1934) included T. scrobiferum as a new species in his aureovestitum subgroup, part of the nitidum species group of Trypargilum . Among the characters he listed to define the subgroup, only one was unique within the subgenus, the long and well developed supraantennal carinae (“limiting keels of the antennal scrobes”) that enclose an area two times as long as broad. In fact, the shape of this carina is almost identical in T. aureovestitum and T. scrobiferum , but T. scrobiferum has characters that are only found in Trypoxylon s.s., as the dorsolateral carina of propodeum, the female hindcoxa with a ventral tubercle, the male VIII sternum shallowly emarginate apically with very short lateroapical apical processes, and the propodeal sternite. As in all other Trypargilum , T. aureovestitum has no dorsolateral carina of propodeum, the female hindcoxa lacks any ventral tubercle or pit, the male VIII sternum is deeply emarginate apically with long apical processes, and has no propodeal sternite. Furthermore, the same characters that suggest placement of T. scrobiferum in Trypoxylon s.s., are also found in T. anapaike , indicating that these two species constitute a natural group, the scrobiferum group.

Diagnosis

Trypoxylon scrobiferum and T. anapaike share the following unique combination of characters: (1) pronotal collar with triangular dorsoposterior median prominence; (2) omaulus present, although short and inconspicuous; (3) subomaulus well-developed, diagonally extending back beyond episternal sulcus; (4) dorsoposterior carina of hindcoxa straight and elevated, ending at coxal apex, not touching trochanter acetabulum; (5) hindcoxa with minute modified area on ventral surface (Figs. 7-9); (6) hind wing with two rows of hamuli separated from each other by more than length of apical row, forewing veinlet 1r-m of submarginal cell forming approximately 90º with vein sector RS+M; (7) propodeum with dorsolateral longitudinal carina (Fig. 10); (8) dorsal border of petiole socket broadened, flat but with deep impressed crescent-shaped area just above the petiole apodeme cavity (Fig. 11); (9) male sternum VIII with proximal half subtrapezoidal and posterior half elongated, with sides nearly parallel, apex shallowly emarginate, with short apicolateral processes (Figs. 1 and 4); (10) gonostylus simple apically, with inner mesal tooth-like projection.

Among these conditions, only two can be regarded as unambiguous synapomorphies supporting the scrobiferum group: the shape of the petiole socket border and the shape of male sternum VIII. The remaining character states may be either symplesiomorphies or homoplasies.