Chironomid biomass determination from larval shape

Ash-free dry weights and dry weights of each larval instar were determined for nine chironomid taxa using unpreserved material. Larval weight (w µg) was related to body length measurements (l mm) by the equation ln w = ln a + b ln l. For a given taxon, the constants ln a and b were dependent on larval size and shape, respectively: b was found to increase with larval length, while taxa with characteristically stout larvae yielded higher values for ln a. Comparison of measurements of freshly-killed chironomid larvae with measurements taken after preservation in 70% ethanol showed no change in body shape due to preservation. Length measurements from larvae preserved in this way are therefore suitable for use in the calculation of larval biomass when the relationship to the unpreserved weight is known. Maximum larval lengths and mean body proportions (length:width ratios) are reported for thirty-two chironomid taxa