1. W.M. Wheeler, Physche6, 216, 233, 253 (1892).
2. A.G. Richards in: Integuments of Arthopods, p. 411. University of Minnesota Press, 1951.
3. F. Romer, Cell Tissue Res.151, 27 (1974).
4. G. Schmidt, Z. Zellforsch.55, 707 (1961)
5. J. Lhoste, Bull. Soc. Zool. Fr.,75, 162 (1950).