Chloropid flies (Diptera, Chloropidae) associated with pitcher plants in North America

Aphanotrigonum darlingtoniae (Jones)

Botanobia darlingtoniae Jones, 1916: 389. Type locality: Mount Eddy, near Sisson, Siskiyou County, California (see Comments).

Aphanotrigonum darlingtoniae: Sabrosky, 1965: 785.

Type material. Lectotype (here designated): M labelled: “Sisson, Cal./Bred. F. M. Jones./VIII-5-1915”; “m# TYPE”; “Type No./20318/U.S.N.M.”; (“Oscinella/darlingtoniae/Type.) Jones” (USNM).

Paralectotypes F: same data as lectotype except “VIII-15-1915”; “f# TYPE”; “Allotype No./20318/U.S.N.M.” (USNM). F: same except: “VII-29-1916” [probably error for 1915]; ‘Botanobia/darlingtoniae/Type] Jones”; red square blank label] (USNM) (See Remarks).

Other material examined. USA: CA: Siskiyou Co. 6 km NW Mt Eddy, Forest Road 17 (41.3573°, −122.5409°), 2,060 m, sweep wet Darlingtonia meadow, 08.vi.2009. J  Mlynarek (5M, 6F, LEMQ), same data except TA Wheeler (3M, 1F, LEMQ).

Diagnosis. (Figs. 1– 2) Aphanotrigonum darlingtoniae can be distinguished from the other described Nearctic species of the genus (A. scabrum (Aldrich), A. trilineatum (Meigen)) by the combination of: dark bristles on gena, three brown stripes on scutum in the shape of a lyre, sides of scutellum also brown (uniformly gray in paratypes of scabrum from Treesbank), interfrontal setulae are darker, more contrasting with frons in darlingtoniae and distinction between gray triangle and yellow anterior part of frons seems less clear in darlingtoniae than in scabrum.

Description (Fig. 1). Total length 2.3–3.1 mm . Overall colour black, frontal triangle brown-black, pollinose, wide, 2/3 length of frons; ocellar tubercle black, pollinose; frons yellow to brown, wider than long; cephalic setae dark, strong but short, frontal-orbital bristles short, black and convergent, two rows of interfrontal setulae inside the margin of frontal triangle; gena wide, anterodorsally yellow, ventrally black, 0.3–0.4 times eye height; eye bare; postgena black, pubescent and 1/5 width of eye; face yellow to brown; scape and pedicel yellow, first flagellomere oval, 1.25–1.35 higher than long, first segment of arista black, rest of arista black, slender and 2–2.5 times width of first flagellomere; palpus yellow, proboscis brown, clypeus black and shiny.

Scutum black with three brown dorsal lines, grey pollinosity, 1.2–1.4 times wider than long, pronotum black, shiny, thin; scutellum black, pollinose, 1.4–1.5 times as wide as long, apical scutellar bristles black and stronger than surrounding setae, on very small tubercles; thoracic pleura pollinose; dorsal margin of anepimeron and lateral region of postscutellum pollinose. Femur black, tibiae yellow with thick black band, metatarsi yellow; femoral organ absent; tibial organ present, black, 0.3 length of tibia. Ratio of costal sectors C1:C2:C3:C4 on wing 1:1.3:1:0.5.

Abdomen black, pollinose, longer than thorax; syntergite 1 + 2 same length as remaining tergites.

Male postabdomen (Fig. 2): small; epandrium in lateral view 1.4 times higher than wide, in posterior view 1.5 times wider than high, setae sparse covering posterior portion of epandrium; surstylus 0.75 times as high as epandrium, parallel sided with a rounded tip, setae short and sparse; cercus square in posterior view, triangular in lateral view, separated by a small evenly rounded arc, bristles short with one long bristle on the posteromedial edge; distiphallus not well sclerotized.

Molecular sequence data. DNA barcodes (658 bp of CO1) for two LEMQ specimens of A. darlingtoniae are available on the Barcode of Life Database (boldsystems.org), (BOLD accession numbers: CCDB-21328-A12/LYMAA1247-14; CCDB-21328-B01/LYMAA1248-14).

Remarks. Jones (1916) recorded the type locality as “Mount Eddy, near Sisson, Siskiyou County, California”. Sisson is the former name for the town of Mount Shasta. There are several populations of Darlingtonia californica in the area surrounding Mount Eddy, west of Mount Shasta, so it is impossible to determine precisely the type locality. The second female type specimen is not labelled as a type either but is assumed and now designated as a paralectotype, because the emergence data matches that given in the original publication. In addition, the determination label is in Jones’ handwriting.

Our 2009 collections occurred early in the season (Fig. 3). Darlingtonia pitchers were small and pale green, in contrast to the previous year’s dark pitchers. There were still patches of snow in the open forest near the collecting site and other herbaceous plants in the vicinity were early in their annual development. Sampling was non-destructive; we swept just above the substrate adjacent to the developing pitchers and over the debris of the previous year’s growth. Jones (1916) based his description of A. darlingtoninae on adult specimens reared from pitchers of D. californica. Our collecting supports Jones’ (1916) suggestion that adults can live outside pitchers and, given the small size of new pitchers, the adult flies may overwinter in the substrate outside the pitchers. Jones (1916) also described the immature stages of A. darlingtoniae, which were subsequently reviewed by Johannsen (1935).

Our collected specimens of A. darlingtoniae from California clusters in the same BIN as Aphanotrigonum trilineatum from Alberta, British Columbia, and New Brunswick. We morphologically compared the two species to confirm the validity of A. darlingtoniae. We also dissected and compared male genitalia. Even though they share the same BIN and molecular barcode, Aphanotrigonum darlingtoniae is morphologically distinct from A. trilineatum supporting the validity of both species.

Tricimba wheeleri Mlynarek new species

LSID: urn:lsid:zoobank.org:act:C9CC48AD-AE7A-49DB-B849-2C64B6C5E812

Type locality. USA: Alabama: Mobile County, 5mi W of Citronelle.

Type material. Holotype M: USA: Alabama: Mobile County, 5mi W of Citronelle, 31.08° N 88.3°W 2.viii.1994, RFC Naczi, Ex. Sarracenia leucophylla (LEMQ). Paratypes: 24 M, 31 F: same as holotype; 1 F: Theodore, 21.vi.1915, FM Jones (USNM); Mississippi: 14 M, 22 F: Stone County, 9mi E of Wiggins, 30.8°N 88.9°W 1.viii.1994, RFC Naczi, Ex Sarracenia alata. (LEMQ).

Other material (not examined). USA. Alabama: Baldwin Co., 0.9 mi NNE of Perdido, 31.0206°N, 87.6234°W, 28 April 1988; RFC Naczi, adults collected from inside upper portions of Sarracenia leucophylla pitchers. (2M 3F, RFCN) Florida: Okaloosa Co., 3 mi S of Crestview, 30.6990°N, 86.5745°W, 19 Aug. 1984; RFC Naczi, adults collected from inside upper portions of Sarracenia leucophylla pitchers. (3M, RFCN).

Diagnosis (Figs. 4–6). Tricimba wheeleri can be distinguished from the other described Nearctic species of the genus by the combination of: shallowly incised scutal lines, and heavily microtomentose gray scutum, expanded distal tarsal segments (Fig. 6).

Description (Figs. 4 and 6). Total length 1.7–2.7 mm. Overall colour brown to black, frontal triangle black, pollinose, 0.4–0.5 times length of frons; ocellar tubercle black, pollinose; frons yellow anteriorly, darkening posteriorly until black, size 1.2–1.3 times longer than wide; cephalic setae slender and pale, frontal-orbital bristles even, interfrontal setulae on margin of frontal triangle; gena yellow, pollinose, 0.2–0.3 times eye height; eye bare; postgena black, pollinose and thin; face brown, as high as wide; scape and pedicel yellow, first flagellomere yellow proximoventrally darkening distodorsally, negligibly higher than wide, first segment of arista yellow to brown, rest of arista slender, brown, sparsely hairy and twice as long as first antennal segment; palpus and proboscis yellow, clypeus brown.

Scutum black, pollinose, with three weakly incised dorsal lines along the dorsocentral and acrostichal lines, covered in fine yellow hairs, 1–1.2 times longer than wide, pronotum black and shiny; postpronotum brown to black; scutellum yellow, round, 1.6–1.8 times as wide as long, apical scutellar bristles black and a lot longer than surrounding setae, on small tubercles; thoracic pleurites brown to black, pollinose; dorsal margin of anepimeron and lateral region of postscutellum pollinose. Legs brown, joints sometimes paler; femoral organ absent; tibial organ present, yellow to black, large, 0.3 length of tibia. Distal tarsal segments expanded, pulvilli enlarged and long tarsal claws. Ratio of costal sectors C1:C2:C3:C4 on wing 1:0.95:0.6:0.5.

Abdomen black, pollinose, longer than thorax; syntergite 1+2 same length as remaining tergites.

Male postabdomen (Fig. 5): large; epandrium in lateral view as high as wide, in posterior view 1.4 times as wide as high, setae densely covering posterior end of epandrium; surstylus 0.8 times height of epandrium, setae short and sparsely covering entire surstylus; cercus large, parallel sided and rounded apically, separated by small evenly rounded arc, bristles short, covering entire cercus; distiphallus small and poorly sclerotized.

Etymology. The species name is a genitive patronym in honour of Terry A. Wheeler, the co-author of this manuscript who passed away during the final stages of this project and contributed much to our knowledge of the Chloropidae. He always said that “this is probably the last species of insect that is associated with North American pitcher plants that needs to be described, how fitting it should be a chloropid”.

Remarks. In addition to collecting a single paratype, FM Jones made notes on additional specimens from Alabama, North Carolina, and South Carolina apparently belonging to this species. Unpublished sketches in the FM Jones archives, deposited in the Peabody Museum of Natural History, Yale University, New Haven, CT, USA (http://harvardforest.fas.harvard.edu/botanobia-darlingtoniae), of specimens collected from Sarracenia drummondii (= S. leucophylla), S. flava, S. minor and S. rubra illustrate the expanded distal tarsal segments, long tarsal claws, and expanded pulvilli.

The type specimens from Sarracenia leucophylla and S. alata were collected as adults from inside the upper portion of the pitchers (RFC Naczi, pers. comm., 2000).

The tarsal modifications are not present in other Nearctic Tricimba species and may be an adaptation for walking on the surface of the debris inside pitchers (Fig. 6).

Folkerts (1999) recorded an undescribed species of “Aphanotrigonum” from Sarracenia species in the eastern United States and that record has been repeated by others (e.g., Dahlem & Naczi, 2006). Although we have not seen vouchers of the specimens referred to by Folkerts, that record likely refers to Tricimba wheeleri. Folkerts (1999) named, but never published, the species from Sarracenia species in the eastern United States as the sister species to Aphanotrigonum darlingtoniae; however, we do not consider it the description as a valid designation of the species and this record appears to be an error based on the conflation of Aphanotrigonum with Bradysia macfarlanei (Jones) (Diptera: Sciaridae), another known inhabitant of Sarracenia pitchers in the southeastern United States. There is, obviously, no evidence of a sister group relationship between the western and eastern pitcher plant Chloropidae, given that they belong to different genera.

Tricimba sp.

Material examined. USA: California: Del Norte Co., Gasquet, 31.iii.1986, emerged 14.iv.1986, D.W. Nielsen, ex larvae coll. in pitchers of Darlingtonia californica (1M, USNM); same data except emerged 23.iv.1986 (1F, USNM).

Remarks. Two specimens identified by Nielsen (1990) as an undescribed species of Nartshukiella (= Tricimba) nr. melancholica (Becker) were reared from a single Darlingtonia californica pitcher (of a total of 124 pitchers sampled) in Del Norte County, California. At the time of collection, flies were sent to C.W. Sabrosky (USNM) for identification and are still deposited in USNM. The specimens are a typical Tricimba melancholica group species. The tarsi are not modified as in T. wheeleri (Fig. 6). Given that only two specimens were reared in the course of a large-scale study of Darlingtonia insect associates, this may have been an opportunistic colonization of a single pitcher plant by a generalist saprophagous species. The association should be considered facultative, and more research into the natural history of this as yet undescribed species is necessary.