Rocetelion fasciola (Coquillett)

Fitzgerald, Scott J., 2019, A Revision of the Holarctic Genus Rocetelion Matile (Diptera: Keroplatidae), Zootaxa 4648 (3), pp. 568-580 : 569-570

Rocetelion fasciola (Coquillett)

Figs. 1 , 3, 4 , 7, 8 , 11 , 12, 13 .

Rocetelion fasciola ( Coquillett, 1894) , p. 126 as Ceroplatus fasciola . HT female (USNM); USA: Washington .

Rocetelion fasciatum ( Garrett, 1925) , p. 12 as Ceratelion fasciata . HT female (CNCI); CANADA: British Columbia. New Synonym .

Type material examined. HOLOTYPE female of R. fasciola ( USNM) ( Figs. 12–13 ): USA: WASHINGTON: “ Was ” [white label] / “ Type / No : 10378 / U.S. N.M.” [red label] / USNMENT / [data matrix code] / 01556000” (additional labels as in Fig. 12 inset) . HOLOTYPE female of R. fasciatum ( CNCI) ( Fig. 11 ): CANADA: BRITISH COLUMBIA: “Cranbrook / BC 11.IX 19 ” [white label] / “C Garrett / Collector ” [white label] / “ HOLOTYPE / Ceratelion / fasciata / Garrett / CNC No. 7879” [red label] / “ MONO / TYPE / CEROTELION / FASCIATA / ♀ / Garrett / C. B. D. Garrett ” [red and white label]. METATYPES of R. fasciatum (these specimens both with Garrett’s original “metatype” labels): CANADA: BRITISH COLUMBIA: Cranbrook, 30 Sept., C. Garrett (1 male, CNCI); Roosville, 27 Sept., Fernie (1 male, CNCI) .

Other material examined. CANADA: BRITISH COLUMBIA: Horseshoe Bay, C.B.D. Garrett , 3 Sept. (1 male), 20 Oct. (1 male)(both CNCI) ; Langford, on window, No. 63.2880.01, 10 Sept. 1963, F.I.S. 1963 (1 male, CNCI) ; Langford, in flight, No. 59.2521.01, 22 Sept. 1959, F.I.S. 1959 (1 male, CNCI) ; Vancouver, Point Grey, J.R. Vockeroth , ex Malaise trap mounted from alcohol, 13 Aug. 1973 (1 female), 11 Aug. 1973 (1 male)(both CNCI) ; Vancouver, Point Grey, J.R. Vockeroth , 25 July 1973 (1 male, CNCI) ; USA: OREGON: Benton Co., 24–28 Aug. 1998, Marys Peak, 1800 ft., N. Fork Rock Creek, S. Fitzgerald, Malaise (1 male, OSAC [0000115152]), 28 Aug. –1 Sept. (1 female, SFC); Benton Co., Corvallis, 1460 SW Allen St. , S. Fitzgerald, 8 Sept. 2012, in window in house (1 male), 12 Sept. 2012, in window in house (1 male), 27 Sept. 2012, in house (1 male), 1 Oct. 2012, in house (1 male)(all SFC; see notes about the probable source of these specimens in “Biology”) ; WASHINGTON: Lewis Co., Iron Creek Campground, 23 Aug. 2016, 46.431067, -121.984794, S. Fitzgerald (1 male, SFC) ; Mason Co., Dewatto, NE Shore Road, 47.441380, -123.076565, 29 May 2018, S. Fitzgerald (1 male, SFC) .

Diagnosis. Males can be distinguished from the similar R. fenestrale by the male terminalia with gonostylus apically acute ( Figs. 3–4 ) and ventromedial membranous area of gonocoxites roughly rectangular, not T-shaped ( Fig. 4 ). Additionally, tergite nine and cerci of R. fasciola are more rounded/oval rather than tergite nine more triangular (broader anteriorly, slightly tapering posteriorly) and cerci more angular (diamond-shaped) in R. fenestrale . Females can be diagnosed from the similar R. fenestrale by tergite 10 small and with a truncate posterior edge ( Fig. 7 ), and sternite 10 broadly rounded posteriorly ( Fig. 8 ). Additionally, males of R. fasciola have the abdomen banded ( Fig. 1 ) while the two known males of R. fenestrale have an unbanded abdomen ( Fig. 2 ).

Distribution (geographic & seasonal). Oregon, Washington, and British Columbia. Laffoon (1965) also lists this species as occurring in California. A single male specimen of Rocetelion that fits R. fasciola in all respects was examined from California (Contra Costa Co., Canyon, 22 Oct., 1981, D. Denning ( LACM)), but as it is missing the tip of the abdomen, the identity of this specimen is not conclusive. Specimens have been collected 29 May–20 October though most specimens are from September and August respectively.

Biology. Unknown. However, four specimens collected at windows inside my home (1460 SW Allen St., Corvallis, Oregon) during several days in September and October may provide some clues to the biology of this species. Shortly before these flies began turning up in the house, my son, Galen Fitzgerald, and I had collected several specimens of the woody polypore Ganoderma oregonense Murrill ( Carpenter 2016) from rotten logs and stumps in an area of mature temperate rainforest on Marys Peak. This area, along the headwaters of the North fork of Rock Creek, belongs to the forest community type Western Hemlock/Devil’s Club Association which is characterized as mature, high volume stands of Douglas-fir ( Pseudotsuga menziesii ), Western Red Cedar ( Thuja plicata ), and Western Hemlock ( Tsuga heterophylla ) ( Franklin et al. 1988). The collected polypore specimens were relocated to Corvallis, brought into the house and set on shelves at room temperature. While no larvae were ever seen on the fungi, I surmise that these fungi were the source of the flies that emerged. Firstly, adult specimens of R. fasciola have been taken in a Malaise trap placed within a hundred yards of the site where the polypores were collected, yet this species has never been found in the multitude of Malaise trap samples that have accumulated from the very different habitat around my Corvallis home down in the valley. Secondly, Chandler (1992) notes that the biology of Rocetelion may be similar to the related genera Cerotelion and Keroplatus “which have slender spore feeding larvae living in slimy webs which they spin on the surface of dead wood and fungi.” In Oregon, larvae of Keroplatus terminalis Coquillett have been observed to go through their entire immature development on the ventral surface of the woody polypore Fomitopsis pinicola (Swartz: Fries) P. Karsten ( Fitzgerald 2004: 370), which is similar in size and habits to the woody polypore Ganoderma oregonense . Additionally, Horsfield (2000) reared the Palearctic Rocetelion humerale from an unidentified polypore on a birch log in Scotland. However, despite having these clues to help direct field work, additional attempts to find the immature stages of Nearctic Rocetelion on Marys Peak, Oregon have been unsuccessful and rearings from Ganoderma oregonense have included only specimens of Sciophila Meigen.

Remarks. Rocetelion fasciola was described from a single female from Washington, USA ( Figs. 12–13 ). Later, an additional specimen of this species was cited by Fisher (1941) from a location that was unclear from the specimen label; the poorly-written label was originally thought to indicate a location in Arkansas ( Fisher 1941), but this was considered erroneous by Matile (1988), who suggested that the specimen more likely came from a similarlynamed site in Washington. The latter suggestion seems the most plausible explanation as all other records of this species are from the extreme western Nearctic.

Although the male of R. fasciola was unknown, Matile (1988) treated the known female specimen as a distinct species noting that “it differs from the other species of Rocetelion in the presence of a distinct antennal apicule, and several other characters, and cannot therefore be conspecific with any of them.” Matile (1988) did not include an explicit list of the material he examined, but states in the introduction of that paper that “the type of R. fasciolum , some of the metatypes of R. fasciatum , and a specimen of R. fenestrale which agrees perfectly with the original description” were studied. Based on this, it is clear that Matile did not study the holotype of R. fasciatum , which, upon study, has an antennal apicule just as R. fasciola . I examined the holotype (“monotype”) and two specimens labelled as “metatypes” (a specimen from the type locality determined by the original author subsequent to the original description of the species ( Evenhuis 2008)) (all from British Columbia) of R. fasciatum ; the holotype has an anten- nal apicule, but the two metatypes do not. This raises the question whether these specimens of R. fasciatum repre- sent a mix of more than one species or if the presence/absence of an antennal apicule varies intraspecifically. After examining additional specimens of Rocetelion from British Columbia, Oregon, and Washington, I suggest the latter is the case as it was found that males with identical terminalia sometimes had and sometimes did not have an anten- nal apicule. The additional characters Matile (1988) suggested to distinguish R. fasciola and R. fasciatum (antennae light brown vs. dark brown, wing strongly darkened vs. faintly darkened, and Sc reaching level of apex of basal cell vs. ending distinctly before apex) were also found to be variable when additional material was studied and therefore do not appear to be useful for species-level determination in this genus. It is likely that Matile (1988) arrived at an erroneous conclusion due to the small number of specimens he had available for study which was not sufficient to understand the intraspecific variation present. The female terminalia of the holotypes of both R. fasciola ( Figs. 12–13 ) and R. fasciatum ( Fig. 11 ) were studied and found to be identical and consistent with Figs. 7–8. R . fasciatum is therefore treated as a junior synonym of R. fasciola .

Figures

FIGURE 1. R. fasciola, male, habitus (British Columbia, Canada). Scale bar = ca. 1.0 mm.

FIGURE 2. R. fenestrale, male, habitus (Alaska, USA). Scale bar = ca. 1.0 mm.

FIGURE 11. R. fasciatum, holotype female, habitus and specimen labels. Scale bar = ca. 1.0 mm (specimen labels not to scale).

FIGURES 3–6. Male terminalia of R. fasciola (3,4) and R. fenestrale (5,6). 3, 5 – dorsal view, 4, 6 – ventral view. Scale bars = ca. 0.5 mm. Abbreviations: cer, cerci; ep, epiproct; gc, gonocoxite; gs, gonostylus; ma, membranous area; T9, tergite 9.

FIGURES 7–10. Female terminalia of R. fasciola (7,8) and R. fenestrale (9,10). 7, 9 – dorsal view, 8, 10 – ventral view. Scale bar = ca. 0.5 mm. Abbreviations: cer, cerci; S7, sternite 7; S8, sternite 8; S10, sternite 10; T7, tergite 7; T10, tergite 10.

FIGURES 12–13. R. fasciola, holotype female, habitus and specimen labels. Scale bar = ca. 1.0 mm (specimen labels not to scale). Photographs courtesy of USNM.