Description of Stenhelmoides mature larva (Coleoptera: Elmidae)

Stenhelmoides is an endemic riffle beetle genus (Coleoptera, Elmidae) of the Neotropical region and its distribution ranges from Mexico to Brazil. The genus comprises 15 species, being Stenhelmoides rufulus the most widely distributed species; the remaining ones are confined to South America and especially to periamazonic lowlands. The immature stages of riffle beetles are poorly known and for the larva of Stenhelmoides has not been described yet. In this contribution, we describe and illustrate the larva of Stenhelmoides from specimens collected in Colombia. Larvae of Stenhelmoides can be easily distinguished from other elmid
genera by the following combination of characters: subcylindrical body-shape; reddish brown color; no stemmata; tegument surface with several spatulate seta and scale-like setae especially on head, sternal region of thorax, legs and first abdominal sternite; length of sensorium on second antennomere variable; anterior margins of head without frontal tooth; open procoxal cavities; one abdominal pleurite; apex of ninth segment strongly emarginated ending in two lateral spinous processes.