Triorla interrupta (Macquart)

Dennis, D. Steve, Barnes, Jeffrey K. & Knutson, Lloyd, 2008, Pupal cases of Nearctic robber flies (Diptera: Asilidae), Zootaxa 1868 (1), pp. 1-98 : 51-53

Triorla interrupta (Macquart)

( Fig. 32 )

Davis (1919) and Osterberger (1930) observed that Triorla interrupta pupae, under the names Erax maculatus Macquart and Erax interruptus , respectively, occur in the soil. The length of the pupal stage varies between 20 and 34 days. Malloch (1917) described the pupal case of a male under the name E. maculatus . The following redescription is based on a female pupal case with a pinned adult from the United States National Museum. It is labeled "8/21 '14; Cage B11."

Redescription: Greatest length, including anterior antennal processes, 18.0 mm; greatest width of thorax 5.5 mm; greatest width of abdomen 5.0 mm, tapering to 2.0 mm at greatest width of abdominal segment 8. Integument subshining golden brown; spines and other processes reddish brown, spurs yellowish brown.

Head with pair of dorsally flattened, ventrally wedge­shaped anterior antennal processes not joined at base and group of 3 basally fused posterior antennal processes located ventrolaterally on each side; middle and outer posterior processes closer together, fused for greater distance, appearing shorter than inner or first posterior process; inner posterior process slightly more acute than middle and outer posterior processes; outer or third posterior process elbowed basally. Labral sheath with small apical keel posteriorly, slightly rugose. Proboscial sheath slightly rugulose posteriorly on each side of midline, with minute median tubercle on each side and median, apically flattened tubercle posteriorly. Maxillary sheath with terminal, apically rounded process posteriorly. Proboscial sheath with small tubercle on each side, slightly below juncture of labral sheath and proboscial sheath.

Anterior coxal sheath irregularly rugulose along margins with anterior, median, longitudinal split. Prothoracic spiracle elongate­oval, situated midlaterally at anterior margin of thorax, projecting above surface of thorax, with ridge­like area anterior to spiracles. Anterior mesothoracic spines on each side of thorax above base of sheath of mid legs; spines short, wide, dorsoventrally flattened and broadly blunt apically with 2–5 furcations. Posterior mesothoracic callosity at base of each wing sheath large, rugose, with basally broad, apically acuminate posterior mesothoracic spine. Wing sheath irregularly rugulose, with small, well developed median tubercle and pair of small, rugose tubercles near posterior margin. Thoracic area above wing sheath smooth to irregularly rugulose. Apex of hind leg sheath reaching to middle of abdominal segment 3.

Abdominal spiracles elongate­oval to crescent shaped, light reddish brown and almost flush with surface, situated along midline laterally.

Abdominal segment 1 with dorsal transverse row of 21 long, apically recurved spurs and 9 bristle­like spines behind spiracle; dorsolateral bristle­like spines absent; venter obscured by wing and leg sheaths.

Segments 2–7 with dorsomedian transverse row of 6 long spurs alternating with 8–21 short, straight spines; spines slightly in front of long spurs; long spurs with basal upraised anterior part; spine numbers decreasing on more posterior segments. Segments 2–7 with 6–11 dorsolateral bristle­like spines on each side and 11–18 long, apically recurved lateral bristle­like spines behind each spiracle.

Segment 2 with 9 ventral bristle­like spines on each side of hind leg sheaths; segment 3 with complete transverse row of bristle­like spines not interrupted by short, wide, hind leg sheath; segments 4–7 with complete transverse row of 29–41 ventral bristle­like spines, some bristle­like spines shorter than others.

Segment 8 with 4 long dorsal spurs on each side of dorsal midline; small spiracle along midline laterally; 11 lateral bristle­like spines; and 2 bristle­like spines on each side of ventral midline.

Segment 9 with pair of long dorsal posterolateral processes curved toward each other, 2 shorter ventral posterolateral processes apically curved toward dorsal posterolateral processes, and 2 ventromedian processes nearly same size as ventral posterolateral processes.

Figures

FIGURE 32. Triorla interrupta (Macquart), lateral view with enlarged dorsolateral views of thoracic region of female and male. Abbreviations: amsp = anterior mesothoracic spine, pmc = posterior mesothoracic callosity, wsh = wing sheath.