Heteragrion majus Selys, 1886

Ramírez, Alonso & Gutiérrez-Fonseca, Pablo E., 2013, The larvae of Heteragrion majus Selys and H. atrolineatum Donnelly, with a key to known species from Costa Rica (Odonata: Megapodagrionidae), Zootaxa 3609 (1), pp. 96-100 : 97-98

Heteragrion majus Selys, 1886

Figs. 1 , 2a, 3a, 4, 5

Material. 1 exuvia (♂, reared), 1 F0 larvae (♂). COSTA RICA: San José province, Braulio Carrillo National Park, Sanguijuela stream (600 m), 10°08’49 N, 83°57’24 W, 26-II-1992, A. Ramírez ; Río Yerba Buena, Moravia, Zurquí de Moravia (1600 m), IV.1995, C. Flores , 1 ♀ and X.1995, J. Ludwing, 1 ♀. Limón, Quebrada Mercedes, Guápiles (200 m), 2006, D. Vásquez , 1 ♂, XII-2006, D. Vásquez, 1 ♀, and 29-IX-2005, G. Vargas, 1 ♀; Río Dos Novillos, Don Eladio, Guápiles (410 m), 30-IX-2005, D. Vásquez , 1 ♀ and XI-2006, D. Vásquez, 1 ♂. Alajuela: Río San Lorencito, San Ramón, Res. Biol. Alberto Manuel Brenes (860 m), 25-XII-2011, P.E. Gutiérrez-Fonseca , 1 ♂ and 31-XII-2011, P.E. Gutiérrez-Fonseca, 1 ♀, 1 ♂; Quebrada Rugama, Nuevo Arenal, Tilarán (550 m). 4-I-2006, P.E. Gutiérrez-Fonseca , 1 ♂.

Description. Larvae uniformly yellow to light brown, body robust, integument densely covered with small setae ( Fig. 1 ).

Head. Wider than long, occipital margin concave, cephalic lobes slightly angulated, covered with setae. Compound eyes black, dorsally and ventrally with a light stripe along the posterior margin. Ocelli separated, frontal one 2x size of laterals. Antennae yellowish without color marks, 7-segmented, 4 th segment longest, relative length of antennomeres: 0.7, 0.8, 0.8, 1, 0.5, 0.3, 0.2; scape and pedicel covered with scale-like setae. Antennomeres 3-7 with ring of fine setae near distal margin ( Fig. 2a ). Labrum with rows of long setae. Mandibles with molar crest, with following formula (sensu Watson 1956): L 1 1' 2 3 4 0 a(m 1,2,3,4,5,6)b, R 1 1' 2 3 4 y ab. Labium prementum-postmentum articulation at level of posterior margin of procoxae; prementum slightly longer than wide (2.5 x 3 mm), without setae except lateral margins that have setae and spines in the distal half. Labial palp with short setae on external margin, ending in 3 apical teeth, basal one shortest and truncated, other two of similar size and shape. Ligula with border slightly serrated, middle V-shaped incision deep and lacking setae or spines ( Fig 3a ).

Thorax. Pronotum with lateral margins expanded and covered with long setae. Anterior and posterior wing pads reaching basal and distal half of S6, respectively. In exuvia, both wing pads reach S5. Femora compressed laterally, with short setae and apical dark spot. Articulation of hind femur with tibia reaches basal level of S7.

Abdomen. Without dorsal protuberances. Posterior margin of S6–10 with row of spines in dorsal view ( Fig. 4 ); ventrally only S10 with row of spines, but this row interrupted in middle ( Fig. 4 ). Male gonapophyses small; female gonapophyses well developed, slightly surpassing distal margin of S10 ( Fig. 4 ). Caudal gills inflated, densely covered with setae ( Fig. 5 ). Lateral gills three faced and with rows of curved spines along each margin. Inner ridge with row of spines limited to distal 0.3. Middle gill with four faces, ventral ridge with spines only in distal 0.3.

Measurements (in mm): Total length without gills: 9–11 (9 larvae), 13–14 (3 larvae), 16–18 (2 larvae); 15 (1 exuvia); posterior femur 4–5; posterior tibia 4–5; maximum width of head 3.5–4; lateral gills 4–5 without filament (6–7 with filament), middle gill 3.5–4 without filament (5.5–6 with filament).

Figures

FIGURE 1. Habitus of the F-0 larval H. majus.

FIGURES 2–5. Details of H. majus and H. atrolineatum. 2) Antennae of H. majus (a) and H. atrolineatum (b); 3) dorsal view of ligula of H. majus (a) and H. atrolineatum (b); 4) dorsal and ventral view of the abdomen and base of caudal gills for H. majus; 5) dorsal view of H. majus caudal gills.