Eye growth in Choneiulus palmatus (Němec) and Nopoiulus kochii (Gervais) (Diplopoda, Blaniulidae)

Developmental stadia of newly moulted individuals of Choneiulus palmatus and Nopoiulus kochii were determined on the basis of the defence glands. The numbers of ocelli and their relative positions also were determined. The first stadium is eyeless, and one ocellus is present in the 2nd stadium. In later moults 0 or 1 and very rarely 2 new ocelli can be formed. In initial moults the probabilities of different types were constant, but after the 7th stadium the probability of a moult without a new ocellus increased strongly, the maximal number of ocelli observed being nine. In 24% of the 497 and 429 individuals of C. palmatus and N. kochii studied, respectively, the eyes had different numbers of ocelli, the maximal asymmetry being in C. palmatus 2 (8 individuals) and in N. kochii 3 (1 individual). The ocular field contains three anterioposterior rows of possible ocular locations, and new ocelli are added at the anterior border of the eye, usually in locations adjacent to already occupied locations. The first ocelli usually form a single row, then new ocelli are added laterally, and all three rows are usually occupied in older individuals. In C. palmatus in 72% of cases growth starts in the ventral row, in 24% in the middle and in 4% in the dorsal row. In N. kochii the respective percentages were 45%, 40% and 15%.