Machimus lecythus (Walker)

Dennis, D. Steve, Barnes, Jeffrey K. & Knutson, Lloyd, 2008, Pupal cases of Nearctic robber flies (Diptera: Asilidae), Zootaxa 1868 (1), pp. 1-98: 84-86

publication ID 10.11646/zootaxa.1868.1.1


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scientific name

Machimus lecythus (Walker)

new combination

Machimus lecythus (Walker)   , new combination

( Fig. 51)

The following description is based on one male and two female pupal cases of M. lecythus   with associated pinned adults from the United States National Museum. All three specimens are labeled "Agawam, Mass.; on 15 VI 15; H.E. Smith collector.” The male is also labeled " W. Springfield No. 915342;" the two females bear similar labels, but with the numbers 915276 and 915332   .

Martin & Wilcox (1965) listed this species among a total of 38 cataloged in the genus Asilus   in North American north of Mexico. Martin (1975) transferred the species to Eutolmus   (misspelled as Eutolmerus), and it thus became the only Nearctic representative of an otherwise Palaearctic genus. In their updated catalog of Nearctic robber flies, Fisher and Wilson (in litt.) have transferred 14 North American Asilus species   to Machimus   , including A. lecythus   . They transferred the other species to Dicropaltum   , Negasilus   , Neomochtherus   , Polacantha   , Prolatiforceps   , and Wyliea   , leaving only Asilus sericeus Say   in an otherwise widespread genus.

Description: Greatest length, including anterior antennal processes, ♂ 16.0 mm, ♀ 16.5–18.0 mm; greatest width of thorax ♂ 3.5 mm, ♀ 4.0 mm; greatest width of abdomen ♂ 3.3 mm, ♀ 3.5 mm, tapering to ♂ 1.0 mm and ♀ 1.0 mm at greatest width of abdominal segment 8. Integument subshining golden brown; 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 subequal, 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; outer posterior process wide entire length, apically blunt to more acute and with oval flat area, with an outer lip basally toward dorsum; inner and middle posterior processes tapering and rounded to more acute apically. Labral sheath rugose with posterior tubercle­like keel. Proboscial sheath smooth to rugulose posteriorly and on each side of midline; with shallow median groove posteriorly separated from small tubercle by area of flattened cuticle. Maxillary sheath rugulose on inner margin, otherwise smooth to irregularly rugulose; posterior processes absent, but sometimes with small tubercle­like swelling on inner margin near middle of proboscial sheath.

Anterior coxal sheath smooth to irregularly rugulose, especially on margins, with anterior, median, longitudinal split. Prothoracic spiracle elongate­oval, directed somewhat posteriorly, on small callosity with small anterior ridge, situated midlaterally at anterior margin of thorax. Anterior mesothoracic spines apically acute, situated above bases of sheaths of mid legs; posterior spine straight, about 2 times as wide as and 1.5–2.0 times as long as posteriorly curved anterior spine. Posterior mesothoracic callosity smooth except for rugose margin, with apically rounded to acute posterior mesothoracic spine. Wing sheath rugose on posterior third, irregularly rugose on anterior two­thirds; basal and median tubercles absent. Thoracic area above wing sheath irregularly rugulose. Apex of hind leg sheath reaching to middle of abdominal segment 3 in female, between middle and posterior margin of segment 3 in male.

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

Abdominal segment 1 with dorsal transverse row of 10–11 long, apically recurved spurs, sometimes with short outer spines; dorsolateral bristle­like spines absent; with 3 lateral bristle­like spines behind each spiracle; venter obscured by wing and leg sheaths.

Segments 2–6 with 1–3 small, short dorsolateral spines on each side and dorsomedian row of 6 long, straight to slightly recurved, apically acute spurs alternating with 5 short, straight spines; spines apically blunt on anterior segments and more acute on posterior segments; segment 7 similar to 2–6, but outermost short spine sometimes absent on 1 or both sides.

Segments 2–7 with 8–12 dorsolateral and 4–7 lateral, straight to apically recurved, unequal bristle­like spines on each side; with fewer bristle­like spines on progressively posterior segments.

Segment 2 with 7–9 recurved ventral bristle­like spines on each side of and extending under hind leg sheaths; segments 3–6 and 7 with complete ventral transverse row of 25–31 and 21–24 straight to apically recurved bristle­like spines, respectively.

Segment 8 of male with 1 long and 1 shorter dorsolateral reddish­brown spur on each side of dorsal midline; segment 8 of female with 1–2 subequal dorsolateral spurs on each side of dorsal midline; both male and female with small, reddish­brown spiracle at lateral midline; with 4–7 lateral bristle­like spines on each side; venter of male with transverse row of 17 bristle­like spines, with outer spines curved toward midline; venter of female with 1–2 ventrolateral bristle­like spines curved toward midline, outermost spines sometimes straight.

Segment 9 with pair of long, recurved dorsal posterolateral processes and pair of short, apically recurved ventral posterolateral processes. Female with pair of fairly long, approximate, terminal posteroventral tubercles; pair of low, basally fused ventromedian tubercles; and pair of low, basally fused tubercles at the junction of abdominal segments 8 and 9. Male with pair of widely separated terminal posteroventral processes, pair of widely separated ventromedian processes, and rugose area at junction of segments 8 and 9.