Asilus sericeus Say

Dennis, D. Steve, Barnes, Jeffrey K. & Knutson, Lloyd, 2008, Pupal cases of Nearctic robber flies (Diptera: Asilidae), Zootaxa 1868 (1), pp. 1-98: 92-93

publication ID 10.11646/zootaxa.1868.1.1


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scientific name

Asilus sericeus Say


Asilus sericeus Say  

( Figs 54–56 View FIGURE 54–56 )

A good description of an Asilus sericeus   female pupal case was given by Malloch (1917). This species was also included in a key to the pupal cases of Connecticut robber flies by Bromley (1946). The following description is based on 3 male and 3 female pupal cases from the United States National Museum and 2 females from the Charles A. Triplehorn Insect Collection, Ohio State University. A male preserved in alcohol without an associated adult is labeled " Asilus sericeus Say   ; Stoughton, Mass.; May 1924; D. H. Blake coll." The other 2 male pupal cases and 2 females from the National Museum are pinned with adults and labeled "Stoughton, Mass.; June 1924; D. H. Blake coll." Among the Stoughton material collected in June 1924, one female case is pinned with an adult male and two male cases are pinned with adult females. The last National Museum female is labeled "Falls Church, Va.; May 13, 23; in earth under rotten manure; pupated May 16, 1923, emerged June 4, 1923." The 2 females from the Ohio collection are pinned with associated adults and labeled "Columbus, O.; issued 6.10.03."

Redescription: Greatest length, including anterior antennal processes, ♂ 14.5–15.5 mm, ♀ 14.5–20.00 mm; greatest width of thorax ♂ 3.5–4.0 mm; ♀ 3.5–5.0 mm; greatest width of abdomen ♂ 2.8–3.3 mm, ♀ 3.0– 4.3 mm, tapering to ♂ 1.0– 1.5 mm and ♀ 1.0–2.0 mm at greatest width of abdominal segment 8. Integument subshining golden brown, wing and leg sheaths darker apically; spines and other processes glistening reddish brown, darker apically except for uniformly colored dorsal abdominal spines; bristle­like spines yellowish to 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 and fused for greater distance, appearing shorter than inner posterior process; inner posterior process usually somewhat thicker than middle and outer posterior processes; outer posterior process with posteriorly lipped, outer, oval flattened area toward dorsum; all 3 posterior processes apically rounded to acute, outer posterior process often more so anteriorly; 1 male with very small middle posterior process almost completely lying against outer posterior process and with small spine­like process between middle and inner posterior process. Labral sheath slightly rugulose, especially along midline, and with elongate, tubercle­like posterior keel. Proboscial sheath smooth to slightly rugulose on each side of midline, with very shallow median groove posteriorly and small tubercle separated from groove by area of flattened cuticle. Maxillary sheath smooth to rugose on inner margin, especially on each side of labral sheath; posterior and median processes or tubercles absent.

Anterior coxal sheath smooth to irregularly minutely rugulose, with anterior, median, longitudinal split. Prothoracic spiracle elongate­oval, directed posteriorly on small callosity with slight anterior ridge, situated midlaterally at anterior margin of thorax. Anterior mesothoracic spines long, subequal, posteriorly curved, situated above base of sheath of mid legs; posterior spine apically rounded, 2–3 times as wide as apically acute anterior spine. Posterior mesothoracic callosity smooth to irregularly rugulose near apically rounded posterior spine, usually irregularly rugulose to rugose on margin, at base of each wing sheath. Wing sheath rugose on posterior third, smooth to irregularly rugulose anteriorly; basal and median tubercles absent. Thoracic area above wing sheath smooth to irregularly rugulose. Apex of hind leg sheath reaching between middle and posterior margin of abdominal segment 3.

Abdominal spiracles reddish brown, elongate­oval, elevated along midline laterally.

Abdominal segment 1 with dorsal transverse row of 12–15 (usually 12) long, apically recurved spurs; sometimes with smaller spur between larger spurs, outer spurs sometimes slightly shorter than others; dorsolateral bristle­like spines absent; with 5–7 lateral bristle­like spines behind each spiracle; venter obscured by wing and leg sheaths.

Segments 2–5 with 1–4 short outer spines on each side and dorsomedian row of 6 long, straight to apically recurved spurs alternating with 4–6 short, straight spines; spines slightly anterior to spurs; median short spine sometimes bifurcate; segments 6–7 with row of 6 long spurs alternating with 7 short spines, with or without short, median, bifurcate spine.

Segments 2–6 with 4–7 (usually 4–5) dorsolateral bristle­like spines and 7–9 lateral bristle­like spines on each side; segment 7 with 2–7 dorsolateral bristle­like spines and 6–8 lateral bristle­like spines on each side; dorsolateral bristle­like spines usually subequal, straight to strongly recurved; lateral bristle­like spines of unequal size, straight to apically recurved.

Segment 2 with 6–8 bristle­like spines on each side of and extending slightly under hind leg sheath; segments 3–7 with complete transverse row of 22–30 ventral bristle­like spines; spines usually long, sometimes short, straight to apically recurved.

Segment 8 with 2 long dorsal spurs and rarely 1–2 dorsolateral bristle­like spines on each side of dorsal midline; small brown spiracle at lateral midline; with 3–5 lateral bristle­like spines on each side; male with median row of 12–16 ventral bristle­like spines; female with 1–2 ventral bristle­like spines on each side of midline.

Abdominal segment 9 with pair of long, recurved dorsal posterolateral processes; pair of short, apically recurved ventral posterolateral processes not fused to dorsal posterolateral processes; and pair of long, widely separated terminal posteroventral processes not joined basally; male with pair of large, widely separated ventromedian tubercles; female lacking ventromedian tubercles.