Alloretochus peruanicus (Soldán), Soldan

Molineri, C., 2014, Description of Alloretochus sigillatus new species with comments and new distributional records for Alloretochus peruanicus (Ephemeroptera, Caenidae, Brachycercinae), Zootaxa 3821 (1), pp. 139-145 : 140-142

Alloretochus peruanicus (Soldán)

Figs. (1A–I, 3A–B)

Cercobrachys peruanicus Soldán, 1986: 343 ; Molineri & Goitía, 2006: 64; Domínguez et al., 2006: 223. Alloretochus peruanicus (Soldán) , Sun & McCafferty, 2008: 78.

Diagnosis. Adult size variable (body length 2–4 mm); body with gray shading widely extended mainly on abdomen (darker on terga I–II and VII–VIII in male) and thoracic sterna ( Figs. 1B–C, E–F ); male subgenital plate broadly emarginated posteriorly as in Figs. 1G–H ; ratios forceps length/subbasal width 6.8–8.0; female sternum IX produced distally but not reaching apex of segment X, distally truncated with small median notch; egg with 7–8 costae in a lateral half ( Figs. 2 H–I).

Material. 7 male and 4 female imagos (parts of a male on slide IBN636CM) from Argentina, Jujuy, Ledesma, río San Francisco, puente a Aguas Calientes, S 23º 42' 42" — W 64º 32' 4", m, 17–18.I.2013, light trap, C. Molineri col.; 1 male imago from BOLIVIA, río Blanco, ca. de Once por Ciento, camino entre Sta. Cruz y Trinidad, S 15º 21' 39.7" — W 63º 17' 28.8", 250 m, 14/VI/2000, E. Domínguez col.; 1 male imago (parts on slide IBN621CM) from COLOMBIA, Dpto Amazonas, P.N. Amacayacu, Qda. Mata-Mata, S 3º 48' 28" — W 70º 15' 21", 2–5.II.1999, at light 4–6 h AM, E. Domínguez, M.C. Zúñiga & C. Molineri cols. All material deposited in IBN. Material listed in Molineri & Goitia (2006) also examined.

Male. Length (mm): body, 2.3–3.8; forewing, 2.0–2.7; caudal filaments, 5.8–9.0. Ratio pedicel/scape, 1.7–2.0. Metanotum with posteromedian finger-like tubercle ( Fig. 1B ). Foreleg with black dot on apex of tibia and tarsus segments 2–3 ( Fig. 1D ). Ratios of length of body: foreleg: midleg: hindleg - 1: 0.6–0.8: 0.4: 0.4–0.5. Ratios of length of forefemur: tibia: tarsus - 1: 1.8–2.3: 1.5–1.7. Ratios of length of foretarsus segment I: II: III: IV: V - 1: 3.6–8.4: 3.0–3.4: 2.6–2.8: 1.8–2.0. Wing length/max width 1.8–2.3. Abdomen with thin and long vestiges of posterolateral projections on segments IV–VI; gray shading darker on terga I–II and VII–VIII. Genitalia ( Figs. 1G–H ): ratios forceps length/subbasal width 6.8–8.0.

Female. Length (mm): body, 4.0–4.5; forewing, 3.4–3.7; caudal filaments, 1.5–1.7. Metanotum with dorsal finger-like tubercle ( Fig. 1E ). Wing length/max width 2.3. Abdomen with vestiges of posterolateral projections on segments IV–VI; abdominal sternum IX produced distally, surpassing half of length of segment X but not reaching its apex; apex of sternum IX truncated with small median notch. Abdominal terga and sterna yellowish, widely washed with gray ( Figs. 1E–F ).

Egg. Shape elongate-ovate ( Figs. 2 H–I), ratios total length/maximum width: 3.0–3.3. Polar cap 1/10–1/5 of whole egg in length, without tubercles. Chorion with 7–8 costae in lateral half. Costa asymmetrical in cross-section (overlapping adjacent inter-costal groove on one side only), costae covered with subcircular wart-like microsculpture (detail in Fig. 2 I). A thin layer that covers the egg (probably not part of the egg, but part of female body cavity) appeared partially detached in most of them, but always presented small circular tubercles (arrow in Fig. 2 H).

Discussion. Sun & McCafferty (2008) differentiated the larvae of Alloretochus from those of all other genera of Brachycercinae by "having a maxillary palp segment 2 that is as long as about 2.3 X the length of the segment 1" (vs. no longer than 2.0 X in the others). In the only larva studied here ( Fig. 1A ), a ready to molt male, maxillary palps roughly coincide with this ratio, with one having a longer segment 2 (2.56X the length of segment 1) than the other (2.25X the length of segment 1) ( Fig. 1I ). Other characters of this larva, including the diagnostic patch of setae on labial palp, are identical to those described by Sun & McCafferty (2008).

Among the characters listed for Alloretochus adults ( Sun & McCafferty 2008), the following were also present in the males studied here: prosternum conically produced ventrally (slightly marked in some specimens), pronotum with slightly convex to nearly straight lateral margin, vestiges of posterolateral projections on abdominal segments IV–VI (in segments I–III poorly developed, not projected), and subgenital plate broadly emarginate and distally membranous.

The small male (body, 2.3 mm, forewing, 2.0 mm; caudal filaments, 5.8 mm) collected in Colombian Amazonas and attributed here to A. peruanicus presents certain differences in relation to males of A. peruanicus from other localities, including the absence of gray shading or other marks on body (except the small black dots at apex of foretibia and tarsal segments, Fig. 1D ), absence of posteromedian projection on metanotum and vestiges of posterolateral projections on abdominal segments. However, the morphology of male genitalia of this individual ( Fig. 1G ) is very similar to that of other specimens of A. peruanicus ( Fig. 1H ).

Alloretochus peruanicus shows a relatively wide range of variation in size and some ratios, as seen in the description above (for example the length of the second fore tarsal segment). This is not rare in the group; and other species may present similar intraspecific variations where specimens are abundant.

In general eggs of A. peruanicus are similar to Cercobrachys fox and C. lilliei (figures 570 and 572, respectively, in Sun & McCafferty 2008).

Distribution. Argentina (Jujuy), Bolivia (Tarija, Santa Cruz), Colombia (Amazonas), Peru (Loreto). Alloretochus peruanicus shows a wide distributional range including medium sized piedmont rivers as the Pilcomayo to larger ones as the Amazon.

Figures

FIGURE 1. A – I. Alloretochus peruanicus: A, larva, ventrolateral view; B male from Blanco river in Bolivia, lateral view; C, male from San Francisco river, Argentina, ventrolateral view; D, foreleg of male from Colombia; E, female (S. Francisco river, Argentina) dorsal view; F, same, ventral; G, male genitalia (Colombian specimen); H, male genitalia (Argentinean specimen); I, larval maxilla.

FIGURE 2. A – G: Alloretochus sigillatus sp. nov.: A, male imago, head and thorax, lateral view; B, same, dorsal view of abdomen; C, same, detail of head; D, male genitalia, ventral view; E, female imago, dorsal view; F – G, eggs. H – I, A. peruanicus eggs.