Corethrella (Corethrella) brakeleyi (Coquillett), 1902

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 173-177

Corethrella (Corethrella) brakeleyi (Coquillett)

Corethra brakeleyi Coquillett 1902a:85 . Type locality: Lahaway, [Ocean Co.], New Jersey, U.S.A. Lectotype ♂, here designated (USNM). Dyar 1902a:200, 1902b:50. Smith 1902:139. Felt 1904:346, 1905:460, 495, 496.

Corethrella brakeleyi: Coquillett 1902b:192 . Dyar and Shannon 1924:215. Johannsen 1903:399, 1934:38. Dickensen 1944:358. Matheson 1944: 92. Cook 1956:58. Stone 1968:185. McKeever and Pound,1979. McKeever 1985a, b, 1986. McKeever and French 1991b:525.

DIAGNOSIS: Male adult: only extant species of Corethrella in the New World with the clypeus nearly square (as in Fig. 18 AF), a distinct midlength wing band, apex of R 2 with dark scales, margin of wing distal to midlength band with discrete dark portions (Fig. 65C), thorax dark brown (as in Fig. 56C), halter pale and lighter than scutellum, midfemur dark brown and equal to that of base of hind femur, base of hind tibia darkly pigmented (contrasting with pale apex of hind femur), tarsomeres all uniformly pigmented (no bands) (as in Fig. 56C), midfemur without scales, abdominal segments 8 and 9 and gonocoxite uniformly dark brown (Fig. 80J) and gonostylus with the subbasal seta very short (Fig. 97B). Female adult: not distinguishable from C. condita ; otherwise only extant species of Corethrella in the New World with the clypeus nearly square ( Fig. 18 AF), flagellomeres 2 and 3 elongate ( Fig. 31I), a distinct midlength wing band, margin of wing distal to midlength band with discrete dark portions (Fig. 71I), thorax dark brown ( Fig. 56C), halter pale and lighter than scutellum, midfemur dark brown and equal to that of base of hind femur, base of hind tibia darkly pigmented (contrasting with pale apex of hind femur) ( Fig. 56C), and midfemur without scales.

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view laterally elongate (as in Fig. 13G). Two large setae on frons between ventromedial area of ommatida (as in Fig. 16B). Antenna medium brown; pedicel with at least one distinctive, more elongate, stout, dorsal or dorsolateral seta; flagellomeres as in Fig. 24F, sensilla coeloconica distributed as in Table 1; flagellomere 13 with well-developed apical bifurcation. Palpus medium brown; segment 3 of nearly constant width. Thorax (as in Fig. 56C): Dark brown, pale sclerites around base of wing. Posterior portion of dorsocentral row with group of about 6 elongate setae. Prescutal suture short, not extending more than half way to dorsocentral row of setae. Anterior anepisternum divided diagonally by sinuous suture, dorsal portion about equal to ventral portion. Ventral portion of posterior anepisternum triangular, uniformly brown, with anterodorsal margin thick. Wing (Fig. 65C): Apex of R 2 basal to apex of M 1. Anterior margin with differently, discretely pigmented scales (indicating anterior margins of wing bands), with subbasal band with dark scales extending posteriorly to margin, varying to some with CuA, A with pale scales, distinct midlength band present, dark scales on apex of R 2, some with dark scales on apices of R 3, R 4+5, M 1, M 2; veins (other than costa and wing margin) with welldeveloped scales. Halter pale. Legs (as in Fig. 56C): Medium to dark brown, with fore-, midleg knees pale, fore-, midtibiae lighter at midlength, hind femur with apical 0.1-0.3 pale, hind tibia pale with basal and apical non-discrete dark brown pigmentation. With only slender setae, lacking scales (except for some in patch of whip-like setae on posterior portion of hind tibia). Midleg with thick, subapical setae on each of at least tarsomeres 1-3. Apices of fore-, midleg fifth tarsomeres undivided, with claws slightly subapical to apical (as in Fig. 75F). Claw of foreleg longer than those of mid-, hind leg. Each claw without inner tooth. Anterior claws of each leg without a basal prong. Foreleg claws unequal. Midleg claws equal. Foreleg third tarsomere shorter than fourth tarsomere. Empodia slender. Abdomen (Fig. 80J): Medium brown. Genitalia (Fig. 97B): Gonocoxite dark brown, strongly tapering; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of setae, with setae 1, 2 thicker than others; setae 1-3 curved at midlength, expanded subapically; with row restricted to dorsal portion of gonocoxite. With one dorsomedial stout seta, tapering from base. Gonostylus (partially extended) curved, tapering from base with apical half slender, somewhat pointed apically; one short, slender, subbasal seta, situated anteriorly or anteroventrally; apical seta slender, short, simple. Aedeagus slender, elongate, tapering gradually to apex, pointed apically, with lateral margins fused near apex.

Female adult. Descriptive statistics: see Tables 6–11. As for male, with following differences. Head: Coronal suture elongate, extending ventrally past ommatida (as in Fig. 16B). Antenna; with flagellomeres as in Fig. 31I, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 18 AF) squarish. Mandible with small, pointed teeth. Palpus as in Fig. 35L. Wing (Fig. 71I). Legs: Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Abdomen: Medium brown with segments 8-9 dark brown. Cercus dark brown.

Pupa. Described by Cook (1956), McKeever and French (1991b). Thorax: Scutum, metathorax each with spherical sensory pit (as in Fig. 100A). Respiratory organ (Fig. 103I): Tubular. Abdomen (Fig. 111B): Segments 3-7 somewhat expanded laterally. Paddle only moderately elongate; apicodorsal thick spine articulating; apicoventral seta longer than thick spine.

Larva. Described by Cook (1956), McKeever and French (1991b).

Egg. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella brakeleyi is known from Massachusetts south along the eastern seaboard of the USA to Louisiana and Florida (Fig. 117A) at altitudes ranging from 0- 91 m. McKeever and French (1991b) additionally recorded this species from further north in Quebec (from Ellis and Wood 1974) and Vermont and further west from Arkansas and Texas, all at altitudes of 152 meters or less. Dickinson (1944) reported specimens from Wisconsin and Rao and Rai (1990) from Michigan. All these additional localities might be those of either C. brakeleyi or C. condita . Unfortunately, the reared male reported by Ellis and Wood (1974) could not be located to positively identify the species collected in Quebec (only 1 larva, 1 ♀ present in CNCI).

Adult specimens studied here were collected using light, Malaise and frog-call traps.

All previous identifications of C. brakeleyi in the following summary of bionomics could equally well apply to C. condita , either because original material was not seen or because females of C. brakeleyi and C. condita cannot be distinguished.

Larvae have been reported from little pools at the head of a swamp spring and from the grassy edge of a lily pond in New Jersey at the type locality ( Smith 1902), ditches, ponds, and a quarry in Louisiana ( Chapman et al. 1971) and a drainage canal in Florida ( Williams and Edman 1968). Ellis and Wood (1974) found larvae in southern Quebec during the summer in either shallow and shaded or deep and exposed sphagnum-mat pools which were about 5°C cooler than nearby pools which were unoccupied. In the fall, larvae were present in all three types of pools. Adult C. brakeleyi were collected emerging from a stand of floating Pistia stratiotes ( Escher and Lounibos 1993) and reared from larvae collected from a small, semipermanent roadside pond, both in Florida ( McLaughlin 1990).

McKeever and French (1991a) reported the relative attraction of different taped frog calls to female C. brakeleyi and found that of Hyla gratiosa to be most attractive (discussed further under “Host specificity”). However, their samples included both and C. brakeleyi and C. wirthi so there is some uncertainty concerning this species’ response to different calls. Similarly, McKeever and French (1991a) studied relative abundances of mixed samples of C. brakeleyi and C. wirthi in traps set at 0.5, 1, 2, and 3 meters above the ground and found these included 48.3% 28.3%, 18.8% and 4.6% of the total number of adult females, respectively. Camp (2006) studied the response of C. brakeleyi females to various calls and his results are discussed more fully under “Evolution of Bionomic Features”.

Williams and Edman (1968) identified blood of birds and mammals in female adult C. brakeleyi but it is unlikely these precipitin tests were accurate. All other evidence indicates that C. brakeleyi , and other Corethrella , fed only on frogs. Female C. brakeleyi have been observed to bite Hyla cinerea ( Johnson et al. 1993) and H. versicolor LeConte (pers. obs.). Camp (2006) analyzed bloodmeals from engorged female C. brakeleyi , using PCR amplification of the vertebrate-specific cytochrome B gene and identified the following hosts: H. avivoca , H. chrysoscelis Cope , Acris gryllus (Harlan) , and Rana clamitans Latreille. Females were observed being attracted to the call of H. versicolor in Quebec by flying when the frog was calling and resting on nearby vegetation when silent. When within about 1-20 cm, the flies walked along the branch to which the frog clung and fed on its toes.

Larvae prey on first and second instar Anopheles quadrimaculatus Say in nature and can consume an average of 3.00–9.32 second instar larvae a day under laboratory conditions ( McLaughlin 1990). Ellis and Wood (1974) found larvae in the laboratory ate small ostracods, first instar chironomid larvae and first instar Culiseta melanura (Coquillett) . Mature larvae do not exhibit surplus killing ( McLaughlin 1990), as do those of C. appendiculata ( Lounibos et al., 2008) . Larvae remain motionless below the surface for long periods and when at the surface, assume a nearly horizontal position ( Smith 1902). Pupae remain at the surface, have little movement, and drown if submerged ( Smith 1902).

McKeever and French (1991a) studied the life cycle of C. brakeleyi in the laboratory and found that female adults produced eggs 5.5 days after taking a blood meal and these hatched in three days. Larvae matured in 16–21 days and the pupal period was 4–6 days. The average number of days for a complete life cycle was 30 days. Smith (1902) reported the pupal stage to be 4.5 days. Corethrella brakeleyi is likely multivoltine ( Table 15), at least in the southern part of its range, with adult records from March till December. McLaughlin (1990) found pupae present in February, March, and July (but not November) in a small pond in Florida. Smith (1902) found fourth instar larvae that pupated at the end of July in New Jersey, USA. and Ellis and Wood (1974) found third and fourth instar larvae from late May till October in Quebec.

Chapman et al. (1971) discovered a lethal iridescent virus in larvae of C. brakeleyi (possibly C. condita ) in Louisiana that was successfully transmitted to conspecific larvae as well as those of C. appendiculata under laboratory condition. Monthly viral infection rates of collected larvae ranged from 0–70% with an average of 36.1%. The equally lethal nematode Corethrellonema grandispiculosum infected 0–39.% of larvae with an average of 17.2% over the year. The annual mortality of the population due to these two organisms was 53.3% and the highest total infection rates for the two pathogens were 86.3 and 79.3% in November and December, respectively. Nickle (1969) noted that most infected larvae of C. brakeleyi have one female and 2- 3 male nematodes but a total of up to six may be present. The nematodes take about nine days to develop, whereupon the fertilized female exits the body of the larva, thereby killing it. Under laboratory condition, the nematode Reesimermis nielseni is a lethal parasite of larvae but it is unknown whether they have an impact in nature ( Ignoffo et al. 1973).

Johnson et al. (1993) reported that female Corethrella brakeleyi feeding on male Green Treefrogs ( Hyla cinerea ) in Florida did not carry Trypanosoma , as did C. wirthi . I have seen females feeding on H. versicolor at Masham Township, Quebec; their mode of feeding is described under the generic discussion of bionomics.

TAXONOMIC DISCUSSION: Males and females were associated through the shared morphology and have been collected together. However, some females may actually be members of C. condita (see discussion below).

The naming of this species is uncertain. The single male lectotype was missing its abdomen and the only features presently separating C. brakeleyi and C. condita are those of the male genitalia. I have arbitrarily considered the lectotype as conspecific with other members of this species. Unfortunately, I was unable to distinguish females C. brakeleyi and C. condita (if I have correctly identified the female of C. condita , see below) but when further, confidently identified specimens become available, perhaps the female paralectotypes would allow for the name to be firmly determined.

I initially thought that C. brakeleyi and C. condita could be distinguished by the presence of a discrete patch of dark scales on the margin of the wing between the apex of M 2 and CuA 1 in C. brakeleyi which was absent in C. condita . The feature worked for all male specimens but for one C. brakeleyi from Falls Church, Virginia, which lacked the patch. In addition, a few specimens had worn wings, making the feature difficult to interpret for these. Further research is needed on fresh, well preserved material to better understand the variation of this feature. If the difference is significant, the lectotype and paralectotypes had a weak but evident patch of dark scales in this region of the wing.

Coquillett (1902a) noted the presence of one male and three females in the type series but did not designate a holotype. I am designating the male as the lectotype, even though it is missing its abdomen. The lectotype and one female paralectotype were previously on pins but have been slide-mounted for this study. Two female paralectotypes, in good condition, remain on pins. All four specimens were said to be reared and these were briefly described by Smith (1902). If exuviae yet exist, they would also represent type material. Cook (1956:60) reported a pupa from the type locality but it is now uncertain where this specimen is located.

Both male and female C. brakeleyi are rather variable in the degree of clypeal shape, distribution of sensilla coeloconica and antennal and wing pigmentation. At least for the females, this may be due to the inclusion of female C. condita (I could not distinguish the two) but I suspect that at least one further species may be present under this name. Some pupae which key to C. brakeleyi in McKeever and French (1991b) vary in shape of the respiratory organ and pigmentation, with one form having the medial portion of the abdominal tergites dark and the respiratory organ more squat. It would be of great value to study further samples of associated larvae, pupae, males and females (especially through rearings from eggs laid by bloodfed females) to better interpret this variation.

McKeever (1985a, b) described the internal reproductive systems of the female and male, respectively and McKeever and Pound (1979) and McKeever (1986) described the female mouthparts of C. brakeleyi (or possibly C. condita ). Reinert (1999) described the dorsal apotome of the pupa.

Although the immature stages described by previous workers as those of C. brakeleyi may actually be those of C. condita , or a mixture of the two, for the phylogenetic analysis I have considered all immatures I have examined as those of C. brakeleyi but these have not been included on the distribution map.

Rao and Rai (1987) described the 6 diploid chromosomes (2n = 6) of C. brakeleyi and Rao and Rai (1990) described this species’ karyotype and amount of nuclear DNA.

MATERIAL EXAMINED: Lectotype, here designated, adult male on microscope slide, labeled “ Corethrella brakeleyi Coq. ”, “ Corethrella brakeleyi (Coquillett) , Lectotype, desig. A. Borkent”, “Type No. 6086 U.S. N.M.”, “Lahaway NJ, VIII-13”, ( USNM). 3 ♀ paralectotypes labeled as for holotype but with VIII-12, VIII-13, VIII-14 respectively (1 on a slide, 2 on pins, USNM) . Other material: 1 ♂, Nag’s Head , North Carolina, USA, 15-V-1954 ( USNM) ; 1 ♂, Berney , Massachuetts, USA, 19-V-1960 ( USNM) ; 1 ♀, Dighton , Massachuetts, USA, 28-VII-1960 ( USNM) ; 1 ♂, Holmes Run , Falls Church, Virginia, USA, 13-IX-1960 ( USNM) ; 1

♀, as previous locality but 3-VII-1960 ( USNM) ; 1 ♂, Louisiana, USA ( CNCI) ; 2 ♀, Chloe, Louisiana, USA, 3- IV-1968 ( CNCI) ; 1 ♀, as previous locality but 21-III-1967 ( CNCI) ; 1 ♂, St. Bernard , Louisiana, USA, 21-XI- 1934 ( USNM) ; 1 ♂, 1 ♀, Harahan, Louisiana, USA, 30-V-1943 ( USNM) ; 1 ♀, Livingston, Louisiana, USA, III-1943 ( USNM) ; 1 ♂, Baton Rouge, Louisiana, USA, 8-IV-1947 ( USNM) ; 1 ♂, as previous locality but 10- IV-1947 ( USNM) ; 1 ♀, as previous locality but IV-1947 ( USNM) ; 1 ♂, 3 ♀, Gainesville, Florida, USA, 20-23- IV-1983 ( CNCI) ; 1 ♀, Gainesville, Florida, USA, 8-22-XII-1986 ( CNCI) ; 1 ♂, Gainesville, Alachua Co., Florida, USA, 20-IV-1967 ( USNM) ; 1 ♀, Vero Beach, Florida, USA, V-1967 ( USNM) ; 1 ♂, Yeehaw, 33 mi W. Vero Beach, Florida, USA, 16-VII-1972 ( USNM) .

DERIVATION OF SPECIFIC EPITHET: The name brakeleyi was proposed by Coquillett (1902a) to recognize one of the two collectors of the types, J.T. Brakeley (originally misspelt by Coquillett).