The epicuticle of millipedes belonging to the genera Cingalobolus and Aulacobolus with special reference to seasonal variations

The diplopods Cingalobolus bugnioni and Aulacobolus excellens possess an epicuticle formed of lipoproteins. But unlike in insect cuticles, the epicuticle lades an outer lipid layer. The epicuticle is found only in the animals collected in summer months. At the commencement of the rainy season the new cuticle that is formed following moulting is without an epicuticle. The periodical presence of the epicuticle is of ecological significance. A study of the transpiration rates using animals with and without an epicuticle showed that in the former evaporation of water through the cuticle was much less than in the latter. It is suggested that the presence of an epicuticle during summer season is of adaptive value in that the restricted permeability properties of the epicuticle enable the animals to conserve their water resources. In the rainy season when there is plentiful supply of water in the environment the animals are without an epicuticle as there is no necessity to restrict water loss. The periodical absence of the epicuticle has been discussed in the light of previous reports on the cuticular organization of millipedes.