A chromosome study of Charaxes jasius L. (Lepidoptera, Nymphalidae)* M. Trentini & M. Marini Institute of Zoology, University of Bologna, via S. Giacomo 9, 1-40126 Bologna, Italy Abstract The haploid chromosome complement of Charaxesjasius is n = 25 in both males and females. The chromo- somes in the mitotic metaphase are rod- and dot-shaped; the primary constriction, even after treatment with hypotonic solution, is lacking in them. Meiosis in females is achiasmatic. Introduction Nymphalidae are well known karyologically among Lepidopteran families: more than 150 species have been studied. The modal chromo- some number is n=31 (Robinson, 1971) cor- responding to the mode in Lepidoptera (White, 1973 p. 412), but among Nymphalidae the 24 stud- ied species of the Charaxinae have a great diversity of chromosome numbers (from n=13 to n=58) with modal number 25-26 (De kesse, 1966, 1967, 1968; De Lesse & Condamin, 1965). The present research is a report on the results ob- tained on the chromosome set of Charaxes jasius both males and females. This species is karyologi- cally unknown and it is the only African species of the Charaxinae to reach the Mediterranean region. Material and methods Eggs, larvae, and adults of C. jasius septentri- onalis Vrty were collected near Livorno (Tuscany) and raised on Arbutus unedo L. in the Institute of Zoology. Karyological observations were carried out on both male and female larvae, pupae, and * This research was supported by a grant from M.P.I. 40%-1984. newly emerged adults. Two techniques were em- ployed in studying testis and ovarioles: a rapod squash method with Carnoy fixation, 45% acetic acid dissection, and aceto-orcein stain, and an air- drying technique (Crozier, 1968 with certain modifications). The detailed procedure is as fol- lows. After 0.05% colchicine pretreatment for 2 h, testis and ovarioles were dissected out and kept un- der 1%0 sodium citrate for 20 min, fixed in 3:1 alcohol-acetic acid, dissociated in 60~ acetic acid on a warmed slide, postfixed in Carnoy fluid, and stained with 2% Giemsa (pH 7) for 15-20 min at room temperature. Besides, dissected testes of new- ly emerged males were fixed in Serra's or Carnoy's fluids, embedded in paraffin, sectioned, and stained with haemalum-eosin or the Feulgen reac- tion. Results and discussion The spermatogenesis of C. jasius starts in the last larval instar and continues in the adults (Fig. 1). In the testis each cyst matures independently of the others, and it is possible to observe both larval testes with some cysts full of spermatozoa and adult testes with some meiotic cysts. The prolonged Genetica 68, 157-160 (1986). 9 Dr W. Junk Publishers, Dordrecht. Printed in The Netherlands.