Biomass and instar estimation of larvae of Phylloicus cressae Prather, 2003 (Trichoptera, Calamoceratidae) in a montane forest stream, northcentral Venezuela

Abstract

Biological and ecological aspects of organisms are important to understand the role of species in aquatic ecosystems. Measuring growth rate is useful to analyse these aspects through the estimation of instar and biomass in aquatic insects like shredder trichopterans. We aimed to produce allometric relationships based on larval body parts and case dimensions to estimate larval instars and biomass for Phylloicus cressae Prather, 2003. Here, we showed that classification tree analysis and power and exponential models proved that dorsal and ventral length of cases were good predictors of larval instars and biomass for P. cressae. We also found that allometric relationships involving the length of the prothoracic mid-dorsal ecdysial suture were suited for assessing larval instars but performing these measurements on cased trichopterans is difficult without damaging them. So, allometric models like ours, based on case dimensions, are invaluable when dealing with live individuals.