Dry mass estimates of some tropical aquatic insects

Relationships of body mass and head capsule width were developed for Thraul odes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Phylloicus sp. Ne ctopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera). The organis ms were collected with a Surber net (0.1296 m(2) and 0.286 mm mesh size) on the Orituco river, Venezuela. The number of specimens used in the analysis for the species studied, was different (from 84 to 103 specimens). Regress ion analysis indicated that all relationships were best expressed by a powe r function rather than by linear or exponential equation. Analyses of the r elationships reveal interspecific differences among insects of the same ord er. Species-specific relationships are recommended to be used whenever poss ible since, depending on the species, the underestimation of mass could be as much as 56%.