Machimus snowii (Hine)

Dennis, D. Steve, Barnes, Jeffrey K. & Knutson, Lloyd, 2008, Pupal cases of Nearctic robber flies (Diptera: Asilidae), Zootaxa 1868 (1), pp. 1-98 : 90-91

Machimus snowii (Hine)

( Fig. 53 )

Scarbrough & Kuhar (1995) described two male pupal cases of Machimus snowii from the University of Delaware Collection. The following, more detailed account is based on six pupal cases of M. snowii with pinned adults from the United States National Museum. Two males are labeled "Spencerville, Ont.; 23­VII­1938; J.M. Smith" and "Newcastle, Del.; 7/23/35; Donald MacGreary Collector; L­32; S.W. Bromley Collection." Four females are labeled "33, S.W. Bromley Collection," "Wellington, Kans.; E.G. Kelly Collector; Webster No. 5445; Cage No. 1867," " Whitesbog, N.J.; 5­3­15; bred specimen; 7­3­15; Quaintance No. 12625; H.K. Plank Collector," and "Reared from a larva maggot found in cranberry turf, maggot endured winter flooding in cranberry bog turf to May 1, 1916, emerged July 13, 1916, died naturally and was pinned July 29, 1916; S.W. Bromley Collection 1955."

Scarbrough & Kuhar (1995) note the following additional features for M. paropus , M. snowii , and M. erythocnemius : basal half or more of anterior antennal process and posterior antennal process rugose; paired thoracic spiracles and first abdominal spiracle reniform.

Redescription: Greatest length, including anterior antennal processes, ♂ 12.0–13.0 mm, ♀ 14.0– 16.5 mm; greatest width of thorax ♂ 3.5 m, ♀ 3.0– 3.5 mm; greatest width of abdomen ♂ 3.0 mm, ♀ 3.0– 3.5 mm, tapering to ♂ 1.0– 1.2 mm and ♀ 1.0– 1.3 mm at greatest width of abdominal segment 8. Integument subshining yellow tan; wing sheath sometimes darker apically; spines and other processes glistening reddish brown, darker apically, except for uniformly colored dorsal abdominal spurs and 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 and middle posterior processes apically rounded to more acute; outer posterior process often wider than inner and middle posterior processes and becoming more acute toward anterior margin, with oval flattened area basally toward dorsum. Labral sheath mostly smooth to slightly rugulose anteriorly and around tubercle­like posterior keel. Proboscial sheath smooth or minutely rugulose, with very shallow median groove posteriorly and small tubercle usually separated from groove by flattened area of cuticle. Maxillary sheath smooth to slightly rugulose along inner margin; posterior processes absent.

Anterior coxal sheath smooth or slight rugulose along inner margin and anterior, median, longitudinal split. Prothoracic spiracle elongate­oval, on small, smooth callosity with small anterior ridge, situated midlaterally at anterior margin of thorax. Anterior mesothoracic spines consisting of pair of subequal, medium length, apically narrow, acute spines above bases of sheaths of mid legs; posterior spine basally wide and straight to slightly curved posteriorly; anterior spine not as basally wide as posterior process and usually strongly curved posteriorly. Posterior mesothoracic callosity smooth to slightly rugulose anteriorly and on margin toward dorsum; with apically rounded mesothoracic spine and often slight swelling toward dorsolateral margin. Wing sheath rugose on apical third, otherwise mostly smooth to irregularly rugulose. Thoracic area above wing sheath smooth to slightly rugulose. Apex of hind leg sheath usually reaching between posterior margin of abdominal segment 2 and middle of abdominal segment 3.

Abdominal spiracles reddish brown, elongate­oval similar to thoracic spiracles, along midline laterally.

Abdominal segment 1 with dorsal transverse row of 10–13 long, apically recurved spurs; some cases with 1 short outer spur on each side; dorsolateral bristle­like spines absent; with 3–5 recurved lateral bristle­like spines on each side; venter obscured by wing and leg sheaths.

Segments 2–6 with 1–6 (usually 1–3) short outer spines on each side and dorsal transverse row of 6 long, narrow, recurved spurs alternating with 5–9 short, wide, straight spines; short spines sometimes bifurcate or occurring in pairs, especially on segment 2, becoming narrower on more posterior segments; with 4–10 (usually 4–6) straight to apically recurved dorsolateral bristle­like spines on each side and 6–8 straight to recurved lateral bristle­like spines behind each spiracle.

Segment 7 without outer spines or with only 1 short outer spine on each side, with row of 4–6 long spurs alternating with 3–5 short, narrow spines; with 3–4 dorsolateral bristle­like spines and 5–7 lateral bristle­like spines.

Segment 2 with 7–11 long, recurved ventral bristle­like spines on each side of and sometimes slightly extending under hind leg sheath; segments 3–7 with complete transverse row of 23–29 straight to apically recurved bristle­like spines of irregular length.

Segment 8 usually with 1 long inner dorsal spur and 1 short outer dorsal spur on each side of dorsal midline, minute brown spiracle at lateral midline, and 3–4 lateral bristle­like spines; male with transverse row of 2–8 ventral bristle­like spines; female with 1 long, inner, recurved spine and 1 short outer spine on each side.

Segment 9 with pair of long, apically recurved dorsal posterolateral processes, pair of small ventral posterolateral processes about half length of dorsal posterolateral processes, and pair of apically reddish­brown, terminal posteroventral tubercles three­fourths length of ventral posterolateral processes; male with pair of small, widely separated ventromedian tubercles; female with pair of minute, approximate ventromedian swellings.

Figures

FIGURE 53. Machimus snowii (Hine), mouthpart sheaths. Abbreviations: lsh = labral sheath, msh = maxillary sheath, prsh = proboscial sheath.