How many larval instars do Raphidioptera have?

The development of two species of Raphidiidae occurring in Central Europe, Raphidia mediterranea H. Aspöck, U. Aspöck & Rausch, 1977, and Ornatoraphidia flavilabris (A. Costa, 1855) was studied by rearing them ‘ab ovo’ in order to clarify the number of larval instars and the length of the larval periods. Raphidia mediterranea represents Type I (pupation after the last hibernation and hatching of adults in spring of the second or third year), Ornatoraphidia flavilabris is a Type II species (pupation in summer or autumn before the last (usually second) hibernation and hatching of adults after overwintering of the pupa in spring of the third year). We found a surprising variability of the numbers of larval instars in both species until pupation, 5 to 12 in R. mediterranea and 6 to 10 in O. flavilabris. There was also a considerable variability in the length of the larval period of R. mediterranea. The enormous variability represents simultaneously a high intrinsic plasticity of the development of Raphidioptera and has been most probably an important precondition for snakeflies to overcome critical situations due to unfavourable environmental conditions.