Caenis burmeisteri Malzacher

Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, Zootaxa 1660, pp. 1-31 : 9-11

Caenis burmeisteri Malzacher ( Figs. 15–30 , 159 , 166 , 173 , 180 )

Caenis burmeisteri Malzacher, 1990: 35 (male).

Material ( IFML). Fifty male and 7 female imagos, and 8 nymphs from ARGENTINA : Formosa, arroyo Torhue, 10 km S de Formosa, 8-XII-1986, E. Domínguez col.; 3 male and 50 female imagos from ARGEN- TINA: Corrientes, Parque Nacional Mburucuyá, Casco Central Estancia, S 28º 03' – W 58º 14', 12-14-XII- 1999, C. Molineri col.

Male imago. A brief description of the new material studied is included because this species was originally described in German ( Malzacher, 1990). Length: body, 2.8–3.2 mm, wings, 2.0– 2.3 mm. General coloration yellowish-brown. Head whitish-yellow shaded with gray at base of mouthparts rudiments, around base of antennae, on posterolateral corners (behind eyes), and on occiput (except on a pale transverse band between lateral ocelli). Antennae: scape yellowish shaded with gray, pedicel and flagellum whitish-yellow. Thorax. Pronotum yellowish-translucent shaded broadly with gray, darker on lateral thirds, with a pair of pale elongated paramedian marks; prosternal triangle pointed anteriorly. Meso- and metanotum yellowish-brown with blackish carinae; pleurae and sterna paler, shaded gray anterior to wing base and around coxal cavities. Legs whitish except longitudinal marginal ridge and apex of fore femora yellowish; all femora with a submedian gray mark and subapical blackish spot, all tibiae shaded slightly with gray on median zone. Wings membrane hyaline shaded gray at base and on veins C, Sc, and R1; remaining veins whitish translucent. Abdomen whitish, terga almost completely shaded with brownish-gray, shaded more markedly toward rear margins of all terga and on median zone of terga I–III and X; pale paramedian subcircular marks present on all terga, black marks present on the otherwise pale pleural folds. Abdominal sterna whitish-translucent. Genitalia ( Figs. 15– 18 ): IX sternum whitish with blackish subtriangular marks on anterolateral corners; styliger sclerite, central sclerite and lateral zones of penes yellowish, remaining parts whitish. Styliger plate posteriorly elongated. Apophyses of styliger sclerite long and narrow ( Fig. 15 ); central sclerite elongated. Posterior margin of penes convex, with a shallow median emargination, lobes laterally blunt. Forceps generally with wide base and narrowing toward the thin and pointed apex, but variable ( Figs. 15–18 ). Caudal filaments whitish-translucent.

Female imago. Length: body, 2.7–3.5 mm; wings, 2.6–3.2 mm. Similar to male imago except epidermal pigments more strongly marked and fore legs conspicuously darker than remaining legs.

Mature nymph ( Fig. 159 ). Length: male body, 3.5 mm; female body, 4.0– 4.2 mm, caudal filaments, 5.5– 8.0 mm. General coloration yellowish-brown. Head ( Fig. 166 ) yellowish, occiput and mouthparts paler, grayish markings forming an irregular net on the occiput, also shaded gray behind eyes. Hind margin of the head with small setae. Antennae: scape and pedicel brownish, flagellum hyaline. Mouthparts: lateral margins of labrum broadly rounded and expanded ( Fig. 20 ), anteromedian emargination shallow and smooth ( Fig. 19 ), mandibles as in Figs. 141–142 , lingua of hypopharynx with fore margin entire ( Fig. 155 ); segment II of labial palp 1.16–1.23 times the length of segment III. Thorax. Nota yellowish-brown with black markings. Pronotum with translucent whitish anterolateral corners, shaded with black on anterior margin and lateral zones; with blackish paramedian dots and median elongated marks. Mesonotum with blackish macula anterior to wingbuds bases, and with a blackish median elongate mark near fore margin; with a pair of submedian pale blotches at center. Legs ( Figs. 23–25 ) yellowish-white, blackish marks present on coxae, trochanters, median zones of femora and tibiae, subapical blackish marks present on femora; coxal projections relatively narrow and broadly rounded, with smooth margins ( Figs. 21–22 ); fore tarsi with 1 row of simple setae, middle tarsi with 1 row of serrated setae, hind tarsi with 2 rows (1 with serrated setae, other with simple setae); tarsal claws I and II with 5–8 large denticles ( Figs. 28–29 ), tarsal claw III with around 40 small denticles, except the apical one, larger ( Fig. 30 ). Thoracic sterna paler, with grayish marks on sterna between middle coxae. Abdomen. Terga ( Fig. 173 ) I–II and VII–X yellowish-brown, terga III–VI yellowish-white, shaded with gray as in male imagos. Median projection of tergum II short and wide at base. Operculate gills translucent yellowishbrown maculated with dark brown spots ( Fig. 27 ), setae from the submarginal ventral row elongated ( Fig. 26 ), dorsal surface smooth and with simple long setae. Abdominal sterna much paler with only small grayish sublateral marks on rear segments ( Fig. 180 ). Sternum IX apically rounded, hind margin with weak bifid setae. Caudal filaments yellowish-white.

Diagnosis. Caenis burmeisteri can be distinguished from the other species of Caenis by the following combination of characters. In the imago: 1) general coloration yellowish-brown; 2) prosternal triangle anteriorly pointed in both sexes; 3) median filament on abdominal tergum II absent; 4) fore legs 0.6 times length of body; 5) forceps apically pointed and basally widened ( Figs. 15–18 ); 6) styliger plate posteriorly elongated, with elongated central sclerite ( Fig. 15 ); 7) apophyses of styliger sclerite long and slender ( Fig. 15 ); 8) penes with convex posterior margin and rounded lobes ( Fig. 15 ); 9) coloration of mesothoracic katepisternum similar to rest of mesothorax. In the nymph: 1) head color pattern as in Fig. 166 , hind margin with small setae; 2) meso- and metacoxal processes present, narrow, with smooth margins ( Figs. 21–22 ); 3) foretarsi with 1 row of simple setae, middle tarsi with 1 row of serrated setae, hind tarsi with 2 rows (1 with serrated setae, other with simple setae); 4) tarsal claws I–II with 5–7 large denticles ( Figs. 28–29 ), claw III with ca. 40 small denticles ( Fig. 30 ); 5) abdominal terga distinctly maculated, pleural folds with black dots; 6) labrum with broadly rounded and expanded lateral margins ( Fig. 20 ); 7) segment II of labial palp 1.16–1.23 times the length of segment III; 8) lingua of hypopharynx with fore margin entire ( Fig. 155 ); 9) sternum IX apically rounded, hind margin with weak bifid setae.

Discussion. This species previously known from Paraguay is here firstly recorded from Argentina . The penes are somewhat laterally acute in original drawings ( Malzacher, 1990), but male imagos from Argentina have penes relatively more rounded ( Fig. 15 ). Also the male imagos here described show longer apophyses in styliger sclerite ( Fig. 15 ). These small differences are here considered as intraspecific variations of C. burmeisteri . The nymphs described here as the immature stages of C. burmeisteri were associated with the adults by a male nymph ready to molt to subimago. This pharate subimago shows the same color pattern and genitalia of the male imagos attracted to the light trap. Additional nymphs of an undescribed species were found in the same locality, also some of them are ready to molt but no adults attributable to this species were caught. Caenis burmeisteri nymphs are similar to C. cuniana Froehlich (also from the lineage with apically pointed forceps, Malzacher 2001), because of the presence of large denticles on tarsal claws, a laterally expanded labrum, linguae of hypopharynx without median emargination, a relatively long third segment of labial palpi, and coxal projections narrow and smooth. Nevertheless, the two species can be separated because operculate gills of C. burmeisteri are heavily maculated and the hind tarsal claws show only small denticles ( C. cuniana present also small bifid setules).

Distribution ( Fig. 186). Argentina ( Formosa, Corrientes), Paraguay.

Figures

FIGURES 15 – 30. Caenis burmeisteri. Male imago: 15, genitalia, v. v.; 16 – 18, detail of forceps, v. v. Nymph: 19, detail of anteromedian emargination of labrum; 20, labrum, d. v.; 21, hind coxa; 22, middle coxa; 23, foreleg; 24, middle leg; 25, hind leg; 26, microtrichia on submarginal ventral row of gill II; 27, gill II, d. v.; 28, foreclaw; 29, middle claw; 30, hind claw.

FIGURES 158 – 161. Nymph, general view: 158, C. argentina; 159, C. burmeisteri; 160, C. dominguezi; 161, C. ludicra.

FIGURES 165 – 166. Nymph, head color pattern: 165, C. argentina; 166, C. burmeisteri; 167, C. dominguezi; 168, C. tenella; 169, C. ludicra; 170, C. plaumanni; 171, C. uruzu.

FIGURES 172 – 178. Nymph, abdominal terga: 172, C. argentina; 173, C. burmeisteri; 174, C. dominguezi; 175, C. ludicra; 176, C. tenella; 177, C. plaumanni; 178, C. uruzu.

FIGURES 179 – 184. Nymph, abdominal sterna: 179, C. argentina; 180, C. burmeisteri; 181, C. dominguezi; 182, C. tenella; 183, C. plaumanni; 184, C. uruzu.

FIGURES 139 – 157. Left and right mandibles, d. v.: 139 – 140, C. argentina; 141 – 142, C. burmeisteri; 143 – 144, C. dominguezi; 145 – 146, C. gonseri; 147 – 148, C. tenella; 149 – 150, C. ludicra; 151 – 152, C. plaumanni; 153 – 154, C. uruzu. Hypopharynx, v. v.: 155, C. burmeisteri; 156, C. dominguezi; 157, C. tenella.