The larvae of Heteragrion majus Selys and H. atrolineatum Donnelly, with a key to known species from Costa Rica (Odonata: Megapodagrionidae) Author Ramírez, Alonso aramirez@ramirezlab.net Author Gutiérrez-Fonseca, Pablo E. text Zootaxa 2013 2013-01-25 3609 1 96 100 journal article 10.11646/zootaxa.3609.1.8 1175-5326 5292698 3C0A4EBB-B8C3-4D9B-9897-3F0300874621 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.