Leucotaraxis, Gaimari & Havill, 2021

Gaimari, Stephen D. & Havill, Nathan P., 2021, A new genus of Chamaemyiidae (Diptera: Lauxanioidea) predaceous on Adelgidae (Hemiptera), with a key to chamaemyiid species associated with Pinaceae-feeding Sternorrhyncha, Zootaxa 5067 (1), pp. 1-39 : 9-10

Leucotaraxis gen. nov.

urn:lsid:zoobank.org:act:C920C4F9-D987-4926-B4FB-C5BB4DC5E7B4

“Undescribed Genus C” – Gaimari, 2010: 1005.

Type species. Leucopis atrifacies Aldrich , by present designation.

Etymology. The prefix Leuco-, in reference to the genus Leucopis , appended with the feminine Greek noun taraxis, meaning “confusion, disturbance.” The name refers to the historical confusion surrounding the proper genus placement of the included species.

Diagnosis. The body is compact and small (2.1 mm or less), but more delicate than typical leucopines. Postocellar and ocellar setae are absent. The frons is flat and meets the lunule at nearly a 90° angle. The fronto-orbital and median areas of the frons have long, erect white setulae, but lack setae. The lunule has a straight to slightly curved upper margin, appearing squared, and in some species is dark brown to black along with the face, parafacial and medial part of the gena. The face has deep antennal grooves and is either all black or all silvery pruinose. The mouthparts are very small and held within the oral cavity above the small cylindrical palpi. The antennae are black. The scutum is entirely silvery-grey pruinose, lacking dorsocentral vittae, and with 2 pairs of dorsocentral setae in the posterior part of the scutum. Prescutellar setae are absent. Prescutellum present. Scutellum concolorous with scutum. The abdominal tergites are dark silvery-grey pruinose, except the dorsal parts of syntergite 1+2 and tergite 3 are bronzy pruinose. In the male genitalia, the phallus is always elongated, and can be either gently or strongly curved, and some species lack a pregonite. In the female, sternite 6 is wider than preceding sternites, tergite 7 is strap-like when present, sternite 7 is arcuate when present, all setulae of the pseudo-ovipositor are tiny, and spermathecae are 2+2.

Immatures. The eggs and puparia are known for three of the species included in this genus, with the following generalities in common. Egg ( Fig. 1A ). With series of 11–13 longitudinal ridges frequently anastomosing into a diagonally reticulated pattern, most densely at posterior pole. Puparium ( Fig. 1B ). The puparium is barrel-shaped, slightly flattened, with a convex dorsal surface which is smooth except for tiny spicules. The dehiscent anterior segments (dorsal and ventral) each slope in lateral view into a thin anterior-most part. Anterior spiracle with slit-like spiracular opening at tip of each of 3–5 finger-like lobes. The posterior spiracles are on separated, raised tubercles with sharp strong spinules in the distal half ( Figs 1C–D ); distally, spiracle trilobed, with slit-like spiracular opening at tip of each finger-like lobe.

Biology. Species of this genus are known as larval predators of Adelgidae on Pinaceae , with three species also associated with aphids in the genus Cinara Curtis. Although never reared from Cinara as prey, adults have been collected from Cinara -infested pines.

Remarks. Contrary to Tanasijtshuk (1986) placing Leucopis adelgivora Tanasijtshuk in his “ argenticollis - group” with an implied close relationship, that species is a typical Leucopis (Leucopis) that happens to feed on adelgids and does not belong to this new genus. In describing Leucopis astonea McAlpine, McAlpine (1977) posited its relationship with the group of species now included in this genus. However, despite several characteristics held in common, it is included in the discrete genus Vitaleucopis , which differs in several substantial respects from Leucotaraxis , including egg and puparial morphology, as well as adult external and genitalic morphology. However, it does seem possible that both genera belong to a complex of related genera with similar feeding habits, also including Anchioleucopis Tanasijtshuk , Lipoleucopis Meijere and Neoleucopis Malloch. The key to species of Leucotaraxis is included as couplets 38–43 in the key to chamaemyiid species associated with Pinaceae-infesting Sternorrhyncha , below.

Figures

FIGURE 1. Immature stages of Leucotaraxis species. A. L. atrifacies, egg, dorsal view, posterior pole right (measure bar = 0.1 mm). B–C. L. argenticollis, puparium, dorsal view: B. habitus (measure bar = 0.2 mm); C. posterior spiracles. D. L. piniperda, puparial posterior spiracles, dorsal view.