Corethrella (Corethrella) wirthi Stone, 1968

Published, First, 2008, The Frog-Biting Midges of the World (Corethrellidae: Diptera), Zootaxa 1804, pp. 1-456 : 184-187

Corethrella (Corethrella) wirthi Stone

Corethrella wirthi Stone 1968:183 . Type locality: Gainesville, Alachua Co., Florida, U.S. A.. Holotype ♀ (USNM). McKeever and Pound 1979. McKeever 1985a, b, 1986. McKeever and French 1991a, b:525.

DIAGNOSIS: Male adult: only extant species of Corethrella in the New World with the clypeus nearly square (as in Fig. 18 AK), flagellomeres 10-12 each with two sensilla coeloconica, a distinct midlength wing band (Fig. 65H), thorax dark brown (as in Fig. 57D), 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 uniformly brown (as in Fig. 57D), midfemur without scales, and segments 8, 9 and base of gonocoxite similarly pigmented and with gonocoxite lightening apically (Fig. 81C). Female adult: only extant species of Corethrella in the New World with the clypeus nearly square ( Fig. 18 AK), flagellomeres 2 and 3 elongate ( Fig. 32B), flagellomere 3 with a sensillum coeloconicum, flagellomeres 9-12 each with two sensilla coeloconica, a distinct midlength wing band, with dark scales basal to the midlength band restricted to anterior veins (so that the scales along the posterior margin of the wing basal to the midlength band are more or less unicolorous, except for some darkened posterior scales at very base of wing) (Fig. 72B), thorax dark brown ( Fig. 57D), 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. 57D), and midfemur without scales.

DESCRIPTION: Male adult. Descriptive statistics: see Tables 2–5. Head: Outline in anterior view laterally elongate (as in Fig. 14C). Two large setae on frons between ventromedial area of ommatida (as in Fig. 16F). Antenna medium brown; pedicel with at least one distinctive, more elongate, stout, dorsal or dorsolateral seta; flagellomeres as in Fig. 24K, sensilla coeloconica distributed as in Table 1; flagellomere 13 with well-developed apical bifurcation. Palpus medium brown, with apex of segment 3 pale, segment 4 somewhat lighter; segment 3 of nearly constant width. Thorax (as in Fig. 57D): Dark brown, pale sclerites around base of wing. Posterior portion of dorsocentral row with group of about 7 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. 65H): 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 R, in some to M, distinct midlength band present; veins (other than costa and wing margin) with well-developed scales. Halter pale. Legs (as in Fig. 57D): Medium to dark brown, with fore-, midleg knees pale, hind femur with apical 0.4–0.5 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 thick. Abdomen (Fig. 81C): Medium brown. Genitalia (Fig. 98C): Gonocoxite medium brown basally, with apical portion more lightly pigmented, parallel-sided for most of length; anteromedial area with spicules similar in length to those elsewhere on gonocoxite; with well-defined dorsal row of setae, with setae 2, 3, 4 slightly thicker than others; with row restricted to dorsal portion of gonocoxite. With one dorsomedial stout seta, more or less of even thickness for most of length, tapering near apex. Gonostylus (partially extended) straight or slightly curved for most of length, somewhat narrowed at midlength, pointed apically; one elongate, slender, subbasal seta, situated anteriorly or anteroventrally; apical seta slender, elongate, bifurcating. 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 short, extending ventrally about midway along area between ommatidia (as in Fig. 16F). Antenna; with flagellomeres as in Fig. 31B, sensilla coeloconica distributed as in Table 1. Clypeus ( Fig. 18 AK) squarish. Mandible with small, apically somewhat squared teeth. Palpus ( Fig. 35Q) swollen apically, pigmentation as for male but in some, entirely medium brown. Wing (Fig. 72B). 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 McKeever and French (1991b). Thorax: Scutum, metathorax spherical sensory pits unknown. Respiratory organ: Tubular. Abdomen: Segments 3–7 somewhat expanded laterally. Paddle only moderately elongate; apicodorsal thick spine articulating; apicoventral seta longer than thick spine.

Larva. Described by McKeever and French (1991b).

Egg. Described by McKeever and French (1991b).

DISTRIBUTION AND BIONOMICS: Corethrella wirthi is known from Maryland south along the eastern seaboard of the USA to Florida (Fig. 117B) at altitudes ranging from 0- 67 m. McKeever and French (1991b) additionally recorded this species from further north in Vermont and further west from Louisiana, all at altitudes of 152 meters or less. Specimens have been collected using light, Malaise and frog-call traps. McKeever and French (1991b) reported C. wirthi from the entire eastern seaboard, as far north as Vermont, at elevations below 152 meters. Hribar and Grogan (2005) noted the presence of this species at the very southern margin of Florida on the Florida Keys and one specimen was confirmed as a female C. wirthi but the other actually belongs in the peruviana species group (see Taxonomic Discussion under C. peruviana ).

Female C. wirthi have been observed to bite Hyla cinerea ( Johnson et al. 1993) , H. femoralis Bosc and Daudin ( Figs. 3A, B), H. versicolor (identified from S. McKeever’s photos), and H. avivoca (identified from S. McKeever’s photos; Fig. 1C). Camp (2006) analyzed bloodmeals from engorged female C. wirthi , using PCR amplification of the vertebrate-specific cytochrome B gene and identified the following hosts: H. avivoca and H. chrysoscelis . Female C. wirthi tend to bite their frog hosts on the posterior half of the frog (legs and lateral abdomen) but have also been observed feeding on the head of H. avivoca (McKeever photo).

McKeever and French (1991a) reported the relative attraction of different taped frog calls to female C. wirthi and found that of Hyla gratiosa to be most attractive (discussed further under “Host specificity”). However, their samples included both C. wirthi and C. brakeleyi 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. wirthi and C. brakeleyi 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. wirthi females to various calls and his results are discussed more fully under “Evolution of Bionomic Features”.

Williams and Edman (1968) found blood of birds and mammals in female C. wirthi (their n. sp. 1) but this is likely a misidentification because precipitin tests, used to identify the blood, may be misleading. Mangold (1978) found females to be attracted to the broadcast calls of the Southern Mole Cricket ( Scapteriscus acletus Rehn and Hebard ) in Florida but this was considered to be likely due to the similarity between the cricket call and that of treefrogs.

Williams and Edman (1968) found a larva of C. wirthi in a “sod sample from maple swamp” in Florida (as n. sp. 1). The immature stages studied by McKeever and Pound (1979), McKeever (1985a, b, 1986) and McKeever and French (1991a, b) were obtained through rearings from eggs laid by field captured, blood-fed females.

McKeever and French (1991a) studied the life cycle of C. wirthi in the laboratory and found that female ovarioles grew less than 4 µm 12 hours after ingesting a bloodmeal but then grew rapidly from about 45 µm to 250 µm after 110 hours. Eggs were produced by 62% of females 3–5 days after taking a bloodmeal and 38% of females laid eggs in the subsequent three days. Eggs hatched in 2–4 days. Larvae matured in 13-24 days, with 75% pupating in 15–19 days. The pupal period was 3–5 days but with 75% emerged in four days. The average number of days for a complete life cycle was 28 days. McKeever (1986) noted that males and females of C. wirthi never fed on proffered 10% sucrose under laboratory conditions.

Female Corethrella wirthi transmit trypanosomes to male Green Treefrogs ( Hyla cinerea ) in Florida ( Johnson et al. 1993) and this is discussed more fully under “ Corethrella as Vectors of Species of Trypanosoma ”.

TAXONOMIC DISCUSSION: Males and females were associated through the shared presence of a common pigmentation and pattern of sensilla coeloconica on the antennae. They have been collected together in Maryland and Florida.

The females I studied from Georgia had lighter palpi and the apices of the midfemora were lighter, perhaps indicating the presence of another species.

Two females from Corcovado National Park, Fila Ceniza, Costa Rica, 260 m, 14-III-6-IV-2003 and two females from Sendero Toma de Agua, Hitoy Cere Biological Reserve, Costa Rica, 100-140 m, 17-XI-17-XII- 1999 (INBC) key to this species. However, they have, in addition to the sensilla coeloconica present in C. wirthi , two sensilla coeloconica on flagellomere 2. Furthermore, the hind femora appear more slender and the apical portion of R 2 has some darker scales. These two likely represent a separate species but more specimens are required to determine whether these differences are consistent. If C. wirthi occurs in Costa Rica, it is somewhat puzzling that no specimens have been collected in the region between the USA and Costa Rica.

Of 9 male, 31 female and one larval and pupal exuviae paratypes originally designated by Stone (1968), I studied 1 male and 29 females. In additional there were three females labeled as paratypes but not listed by Stone (1968) but which were almost certainly studied by him (they have the same paratype labels as the others). The specimens were collected at Lake Worth , Florida on 7-VIII-1951 (1 ♀) and 9-VIII-1951 (2 ♀) .

McKeever (1985a, b) provided detailed studies of the internal reproductive systems of female and male C. wirthi , respectively. McKeever and Pound (1979) and McKeever (1986) described the male and female mouthparts of C. wirthi . Reinert (1999) described the dorsal apotome of the pupa.

A portion of the ribosomal DNA of C. wirthi was analyzed by Miller et al. (1997) and Aransay et al. (2000). The results are discussed in the phylogenetic analysis below.

MATERIAL EXAMINED: Holotype, adult female on microscope slide, labeled “ Holotype Corethrella wirthi USNM 69870 Stone”, “Gainesville, Fla, 19 April 1967, W Wirth - light trap” ( USNM). Paratypes: 1 ♀, pinned, Miami, Florida , USA ( USNM) ; 1 ♀, pinned, Miami, Florida , USA, 20-II-1944 ( USNM) ; 1 ♀, pinned, Miami, Florida , USA, 26-VII-1944 ( USNM) ; 1 ♀, Miami, Florida , USA, 7-X-1944 ( USNM) ; 3 ♀, 2 ♀ pinned, Miami, Florida , USA, 14-X-1944 ( USNM) ; 1 ♀, 2 ♀ pinned, Miami, Florida , USA, 17-X-1944 ( USNM) ; 1 ♀, 10 ♀ pinned, Miami, Florida , USA, X-1944 ( USNM) ; 1 ♀, pinned, Avon Park, Florida , USA, 6-VIII-1942 ( USNM) ; 1 ♀, pinned, Marianna, Florida , USA, 17-IX-1943 ( USNM) ; 1 ♀, pinned, Marianna Air Base, Florida , USA, 3-XI-1944 ( USNM) ; 1 ♀, pinned, West Avocado, Dade Co., Florida , USA, 16-X-1944 ( USNM) ; 1 ♀, pinned, Morrison Field, West Palm Beach, Florida , USA, 10-XII-1942, ( USNM) ; 1 ♂, pinned, Vero Beach, Florida , USA, V-1967 ( USNM) ; 1 ♀, pinned, Lake Worth, Florida , USA, 7-VIII-1951 ( USNM) ; 2 ♀ (one pinned) from previous locality but 9-VIII-1951 ( USNM) . Additional material: 9 ♂, 18 ♀, Wango , Wicomico Co., Maryland, 16-23-VIII-2004 ( CNCI; 7 ♀ pinned) ; 9 ♀, pinned, Camp Lejeune, Jacksonville , North Carolina ( USNM) ; 1 ♂, pinned, Nag’s Head , North Carolina, 15-V-1954 ( USNM) ; 1 ♂, pinned, Lahaway, New Jer-

sey ( USNM) ; 1 ♀, Sapelo Island, McIntosh Co., Georgia , USA, 9-29-V-1987 ( CNCI) ; 2 ♀, Statesboro , Georgia, USA, 4-V-1978 ( CNCI) ; 1 ♀, pinned, Billy’s Id, Okefenokee Swamp , Georgia, VI-1902 ( USNM) ; 1 ♀, Crystal River, Citrus Co., Florida , USA, 7-VI-1949 ( USNM) ; 1 ♂, 1 ♀, Gainesville, Florida , USA, 8-22- XII-1986 ( CNCI) ; 2 ♂, 1 ♀, as previous locality but 21-31-XII-1986 ( CNCI) ; 1 ♀, Key Largo, Monroe Co., Florida , USA, 7-X-1999 ( FSCA) ; 2 ♂, Raft ( Raft River ), Baldwin Co., Alabama, 30° 77' N, 87° 95 W, 24- VIII-2000 ( CNCI) ; 2 ♂, from previous locality but 31-VIII-2000 ( CNCI) ; 1 ♂, from previous locality but 24- VIII-2000 ( CNCI) ; 5 ♂, 1 ♀, from previous locality but 26-IX-2000 ( CNCI) ; 1 ♀, Big Lizard Creek , Baldwin Co., Alabama, 30° 52' N, 87° 57'W, 16-IX-2001 ( CNCI) ; 2 ♂, Bymes ( Bymes Lake ), Baldwin Co., Alabama, 30°79'N 87°91'W, 14-X-14, 2000 ( CNCI) ; 2 ♂, from previous locality but 5-IX-2000 ( CNCI) ; 1 ♂, from previous locality but 21-IX-2000 ( CNCI) ; 2 ♀, from previous locality but 18-VII-2000 ( CNCI) ; 3 ♂, Little Briar Creek , Baldwin Co., Alabama, 30°84'N 87°94'W, 18-VII-2000 ( CNCI) .

DERIVATION OF SPECIFIC EPITHET: The name wirthi was proposed for Willis W. Wirth.