Investigations on the life‐history of the stonefly Dinocras cephalotes Curt. (Plecoptera: Perlidae)

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Abstract
The life history of Dinocras cephalotes was investigated in a quantitative one‐year‐study in a river in the Swiss lower Alps and by growth studies in the laboratory. The relative growth between the instars is smaller for the males than for the females and decreases with increasing body size. By means of a growth model it is shown that there are 17 larval instars for the males and 18 for the females (95% confidence limits 15–20 and 17–21 resp.). Measurements of the wing pad size indicate that the males pass through fewer instars than the females. The life cycle of D. cephalotes lasts three years, of which almost one year is spent in embryogenesis. A survival rate of 85–90% was found per instar. The growth of this stonefly reaches a maximum in summer and drops to practically zero in winter.