Abstract
Stenhelmoides Grouvelle is a Neotropical genus of Elmidae and although it exhibits a wide distribution, until now no larvae had been associated with adults of this genus. Larvae, very likely belonging to this genus, were associated based on co-occurrence with adults. Eleven larvae and nine adults were examined from ten localities at altitudes between 30 and 682 m a.s.l. in the Andean, Caribbean and Pacific regions in Colombia. Mature larvae of the Stenhelmoides rufulus (Hinton) are described and illustrated for the first time. A larval diagnosis for the genus is presented; body shape, distribution and form of setae and number of pleural sclerites are diagnostic characters for larvae of this genus. Comparative notes with similar larvae of other Elmidae genera are presented. The existing generic keys are updated to include larvae of Stenhelmoides. Comments on distribution and habitat of Stenhelmoides larvae are also provided. This work contributes to enhance the knowledge of Neotropical larvae, which have been described for only approximately 56% of genera and 8% of species of Elmidae.
Highlights
Riffle beetles (Coleoptera, Elmidae) are common dwellers of running waters and constitute an important component of benthic macroinvertebrate communities[1]
The same can be said for several other genera of Neotropical riffle beetles, a detailed revision of distributional data was performed in order to rule out the possibility that this larva could belong to another genus
Abdomen with a single pair of pleural sclerites on first segment; sternopleural and tergopleural sutures incomplete on second abdominal segment; abdominal segments wider than long; segment IX ending in two spinous processes with an emargination in the middle
Summary
Riffle beetles (Coleoptera, Elmidae) are common dwellers of running waters and constitute an important component of benthic macroinvertebrate communities[1] They are considered effective bioindicators of water quality and commonly used in ecological studies. The Neotropical region is characterized by a high-level of endemism and great diversity of Elmidae with around 50 genera and 500 species[21] One of those Neotropical genera is Stenhelmoides Grouvelle, 1908, with 15 described species and a wide geographical distribution. Adult Stenhelmoides are distinguished from other Elmidae by the following combination of characters: dorsal tomentum over pronotum and elytra, with an oval area without tomentum in the middle of pronotum, the lack of carinae or depressions on pronotum and the presence of granulose rows on elytra without forming carinae[22] Prior to this contribution, the larva of Stenhelmoides was undescribed. Taking in account the co-occurrence of these larvae with adults of Stenhelmoides rufulus, the larvae here described can be assigned to this species with a good degree of confidence
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