Syringogastridae Prado 1969
Creators: name: Lonsdale, Owen
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Syringogastridae

description: Syringogastridae Prado, 1969
(Figs 124–142, 404)
Type genus: Syringogaster Cresson 1912: 392, by Prado (1969: 1). Type species of genus: Syringogaster rufa Cresson, 1912: 393, by original designation.
Syringogastridae is a small, well-defined family of 22 extant and two fossil species in the genus Syringogaster that was last revised by Marshall et al. (2009). Marshall et al. (2009) described 11 new species and divided the genus into four species groups following a phylogenetic analysis, with one of these groups consisting of the two known fossil species discovered in Dominican amber. Species are found throughout the Neotropics, with S. subnearctica Feijen narrowly extending into Nearctic Mexico.
Biology. Most species are found below 800m (but rarely up to 1400m) in lowland tropical forests, often on or underneath large leaves. Adults are uncommonly encountered but they can be abundant locally, sometimes as multispecies assemblages; while most are found singly, they sometimes occur in large groups, possibly representing mating aggregations (Marshall et al., 2009; Marshall & Buck, 2010). Adults have been attracted to sprayed maple syrup solutions and collected at extra-floral nectaries (Marshall et al., 2009). “Bubbling” behaviour between mating pairs been observed, and females in mating aggregations were seen with swollen abdomens that were perhaps filled with honeydew (Marshall et al., 2009). Large numbers of one species were collected on “low, lush vegetation flanking a sea-level path”, and other specimens have been collected in primary forest, secondary forest, a garden, a swampy area at a forest edge, on foliage and “on pendulous Heliconia inflorescences” (Marshall et al., 2009). Adults resemble pale to dark ants, a similarity exaggerated by their wing shape and pattern; field observations report very accurate ant-like walking behaviour (Papavero, 1964; Marshall et al., 2009; Marshall & Buck, 2010). Larvae and puparia are unknown, but eggs of S. atricalyx (photographed) and S. lopesi are described in Marshall et al. (2009), and the egg of an unidentified species is briefly described in Meier & Baker (2002).
Immature stages. Unknown.
Adult Diagnosis. Small, slender, ant-like (Figs 124–128); wing length 4.0–6.0mm. Colour yellow to dark brown or partially patterned. Inner verticals, fronto-orbitals, postocellars, vibrissae and most thoracic setae absent, excluding apical scutellar and posterior supra-alar. Antenna elbowed with first flagellomere slightly elongate; pedicel with dorsal seam. Back of head with supracervical collar and anterior portion of pronotum produced into short “neck”. Thorax mostly smooth; with sharp humeral and supra-alar carinae; posterior spiracle with surrounding ridge and processes. Precoxal bridge present; postmetacoxal bridge present; thorax produced at narrow point of attachment to abdomen. Enlarged hind femur with two rows of spines ventrally; hind tibia curved and with double sclerotized ridge ventrally (separate, not united as in Megamerinidae); fore and mid femora with row of glands posteroventrally (Fig. 129); mid and hind tarsi with “sawlines” (Fig. 125). Wing variably patterned; alula absent; upper calypter margin pubescent, not long-haired; sc incomplete; costa unbroken (Fig. 404). Abdomen petiolate with segments 1–3(4) fused; external terminalia small, on underside of abdomen.
Adult Definition. Wing length 4.0–6.0mm. Ant-like, with form accentuated by slender petiolate abdomen and narrow patterned wings closely appressed to body (Figs 124–128). Colour yellow or reddish-orange with brownish to dark brown pattern, sometimes mostly dark and/or with light yellow to white legs.
Chaetotaxy: 0 inner vertical; 1 outer vertical; 0 fronto-orbitals; 0–1 ocellar (short to very long); 0 postocellars; vibrissa absent, but vibrissal angle sometimes with prominent setae. 0 presutural intra-alars; 0 postpronotals; 0 anterior notopleurals; 0–1 small, setula-like posterior notopleural; 1 posterior supra-alar (on minute tubercle); 0 posterior intra-alars; 0 dorsocentrals; 0 acrostichals; 1 scutellar (on minute tubercle); 0 proepisternals; 0 anepisternals; 0 katepisternals. Parafacial and pedicel without outstanding setae. Back of head microsetulose. Metanotum and dorsal regions of pleuron microsetulose (remainder of pleuron glabrous); pleuron with scattered thin setae that are concentrated anteroventrally and on metapleuron, and on femora and abdomen. Posterior spiracle with dense setulae and several golden hair-like setae. Fore femur with anteroventral row of 2–12 small, stout pointed spinules, and sometimes with single posteroventral spinule; distal posteroventral margin also with rows of gland openings (Fig. 129). Hind femur with with both anteroventral and posteroventral rows of 4–15 spinules. Fore tibia with short brush of densely clustered pale setulae. Mid tibia with small ventroapical seta. Mid and hind tarsi with “sawlines” (longitudinal rows of dark, flattened setae; Fig. 125)—present on anterior and posterior surfaces of basal 3–4 tarsomeres on mid and hind legs, excluding posterior surface of hind basitarsomere.
Head. Head partially globose with back of head mostly to partially flat. Antenna elbowed; pedicel with dorsal seam; first flagellomere elongate (2–3 times longer than wide), flat, dorsally carinate; arista sparsely short plumose (possibly bipectinate). Ocellar triangle glabrous or tomentose, nearly attaining anterior margin of frons; orbital plate not differentiated; remainder of frons matte and minutely setulose with setulae sometimes slightly longer anteromedially (never appearing as interfrontals); ocelli separated from vertex by area approximately as long as tubercle. Face narrow; microscales occurring at least medially; gena shallow; parafacial narrow, tomentose. Clypeus large, prominent; palpus narrow, subcylindrical. Back of head with short collar derived from semicircular carina with dorsomedial patch of microsetulae. Anterior ommatidia enlarged.
Thorax. Pronotal collar present, meeting corresponding process on back of head. Proepisternum shifted dorsally, displacing postpronotum posteriorly. Scutum with humeral and supra-alar carinae; notopleural and anepisternal junction sometimes also with carina (“notopleural carina”); scutum slightly bulging lateral to dorsocentral rows, sometimes obvious as one pair of flat ovate notopleural and supra-alar pads. Katatergite flat. Precoxal bridge present with suture between prosternum and proepisternum absent, setulose laterally, surface raised; postmetacoxal bridge present, fused to metasternum between hind coxae. Scutellum small, short, preceded by deep anterior and lateral grooves; subscutellum vestigial to absent. Greater ampulla absent. Metanotum with high, narrow cylindrical process meeting abdomen. Posterior spiracle prominent; flanked ventrally by bilobed ridge and anteriorly by two processes separated by circular notch.
Wing. (Fig. 404) Narrow, slender, wth alula and anal lobe highly reduced. Patterned with three coalescing transverse bands, or dark with three clear transverse spots. Vein bm-m absent or faint. CuA straight to shallowly rounded. Cell cu a exceeding bm by usually more than length of CuA+CuP. M 4 not reaching wing margin; CuA+CuP some- times absent or reaching wing margin as weak vein or fold. Costa unbroken; sc incomplete, sometimes partially coalescing with R 1. Calypter reduced with short to medium-length hairs.
Legs. Legs slender with hind femur swollen; hind tibia correspondingly curved and stout with two ventral rows of black sclerotized ridges (separate, not fused), apically with shallow triangular process. Fore coxa broadly separated from mid coxa, inserted ventrolateral to shallow collar. Fore and mid femora with posteroventral row of gland openings; glands clustered in circular pits (often along distinctly raised surface), with ducts long, narrow and with slightly widened apical chamber (Fig. 129).
Abdomen. Abdomen petiolate, widest past T3 and narrowed at pregenital segments, under which the terminalia is partially to mostly hidden (Figs 140–141); T3 and sometimes also T4 fused to syntergite T1+2, suture past T1 and sometimes T2 absent. Sternites much narrower than tergites, sometimes weakly sclerotized and mostly indistinct aside from presence of setae; wider than long past segment 4; S1 with very small, dark transverse posterolateral ridge. Spiracle 1 in margin of tergite, spiracles 2–4 in membrane, spiracles 5–7 variable.
Male genitalia. (Figs 134–139) S6 of variable shape, sometimes reduced or medially divided. S8 short, bandlike, fused to narrower, ventral S7, essentially symmetrical, enclosing 7 th spiracles. Epandrial sides often subparallel medially and sometimes with one pair of marginal dorsolateral lobes. Cerci small but well-developed, usually fused along most of length. Surstylus movable, usually more than half length of epandrium, often rounded apically, sometimes narrow. Subepandrial sclerite reduced to one pair of small lateral sclerites connected by broad membrane. Hypandrium with arms joined posterodorsally and anterior bridge usually complete; setose with pronounced ventrobasal lobe. Phallapodeme well-developed, slightly carinate apically; usually separate from hypandrium, with slender processes (“phallic guides”) reaching hypandrium. Pregonite lobate, setulose, articulating with hypandrium. Postgonite dark, rod-like, extending from base of phallapodeme to pregonite. Basiphallus large, wedge-shaped. Epiphallus absent. Distiphallus broad with apex sac-like, twisted and spinulose; with one pair of ventral bands. Ejaculatory apodeme with pale blade sometimes reduced, stem sometimes with medial setula-like structures; sperm pump shallow, venter with ill-defined sclerotization sometimes cup-like, sometimes extending to base of duct.
Female genitalia. (Figs 140–142) T7 and T8 short, wide. T10 and S10 simple, short. Terminal segments short, barely telescoping. Cercus narrow, relatively long and thin. Spermathecae telescoped and transversely wrinkled, in two pairs on long duct with short apical branches (paired bodies close, contiguous or fused); spermatheca and apex of duct pigmented. Ventral receptacle short, sac-like. Apex of genital chamber with lightly sclerotized dome (“vagi- nal plate” in Marshall et al. (2009)) arched over shallow laterovental elaborations of membrane.
description: Published as part of Lonsdale, Owen, 2020, Family groups of Diopsoidea and Nerioidea (Diptera: Schizophora) - Definition, history and relationships, pp. 1-177 in Zootaxa 4735 (1) on pages 32-34, DOI: 10.11646/zootaxa.4735.1.1, http://zenodo.org/record/3670762