Heteragrion atrolineatum Donnelly, 1992

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 : 99

Heteragrion atrolineatum Donnelly, 1992

Figs. 2b, 3b

Material. 1♂ exuvia (reared). COSTA RICA: Limón province, Guápiles, Dos Novillos stream, Don Eladio (410 m), 10°12’46 N, 83°35’ 29 W . 16-IV-2006. P. Gutiérrez leg.

Description. Larvae uniformly light brown, body robust with cylindrical abdomen, integument densely covered with small setae, as in H. majus .

Head. As in H. majus , but with following differences: Cephalic lobes with short setae. Antennae 7-segmented, 3 rd segment longest, relative length of antennomeres: 0.7, 0.7, 1, 0.8, 0.4, 0.3, 0.2. Antennomeres 3-7 without rings of fine setae ( Fig. 2b ). Mandibles as in H. majus , but L 1 1' 2 3 4 0 a(m 1,2,3,4,5)b. Prementum longer than wide (2 x 3 mm). Labial palp with few short setae on external margin; middle one of 3 apical teeth longest. Ligula with median incision U-shaped ( Fig 3b ).

Abdomen. As in H. majus , but posterior margin of abdominal S6–8 with row of strong setae in dorsal view; S9–10 with row of spines. Ventrally, S9–10 with incomplete row of spines in ventral view, more evident toward margins. Gills as in H. majus .

Measurements (in mm): Total length without gills: 13 (larvae); posterior femur 4.0; posterior tibia 3.5; maximum width of head 3.0; lateral gills 5 without filament (7 with filament), middle gill 4 without filament (6 with filament).

Remarks. Larvae of both species were found among accumulations of detritus on the stream bottom, under rocks or where leaf litter accumulated. Streams were 1–2 m wide and had abundant cobbles and continuous water flow, surrounded by forest.

Figures

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.