Odonatological Abstracts

(3154) CHAPPELL. R.L., A D. KLINGMAN & M M. BELL, 1973, Neurophysiology and development of the dragonfly median ocellus. Proc. N.Y. ent. Soc. 81 (1): 63. — (Dept. Biol. Sei.. Hunier Coll., City Univ. New York. Room 210, 695 Park A ve. New York. N. Y. 10021. USA). This is abstract of the programme, "The cyclops eye of the dragon fly", presented at the meeting of the New York Ent. Soc., Feb. 20, 1973. — [Verbatim]; The role and development of the dragonfly median ocellus are discussed in light of recent neurophysiological evidence obtained from intracellular recordings of receptors and postsynaptic units and from electron micrographs of synaptic organization. Behaviorally, dragonflies whose ocelli were occluded in the field flew up to a branch and remained there as long as they were observed (one hour) while those whose compound eyes were occluded flew skyward until they disappeared from sight, indicating possible roles in diurnal behavior and phototaxis. On the basis of neurophysiological recordings and feedback synaptic organization, an additional role as a shadow or motion detector was suggested. A study of the development of a population of 32 nymphs of Aeshna tuberculifera revealed that while the presumptive lateral and median ocelli could not be identified prior to the fourth day of the final instar, they could always be found after the eighth day of the final instar. The mean duration of the final instar was 30.4 days (standard deviation of 6.6 days) for a population of 245 dragonflies of the species Aeshna tuberculifera and Anax junius. The preceding instar (instar -I) had a mean duration of 16.8 days (standard deviation of 3.6 days) for a population of 100 dragonflies. For ten dragonflies reared through instar -2, the mean duration of that instar was 15.1 days. Developmental study suggests the possibility of severing the ocellar nerve prior to emergence in order to obtain denervated adult ocelli for neurophysiological study. (3155) GANDHI, Y„ 1973. Chromosomal studies of five species of Odonata (damsel and dragon flies). M.Sc.thesis, Panjab Univ., Chandigarh. IV+91 pp.. figs excl. — ( Author's aMress unknown). This is a very detailed study of the male gonial chromosome morphology and behaviour, with special reference to the chiasma frequencies in Ceriagrioncoromandelianum (Delhi and Chandigarh; n=!4), Rhodischnura nursei (Chandigarh; n=!4, m), Brachythemis contaminataf Delhi; n= 13, m), Crocothemis servilia (Chandigarh; 2n=27, n=!3, m) and Trithemis festiva (Chandigarh; n=13, m). The paper also contains a brief outline of the history of the cytogenetic work on Odon., and a catalogue (incomplete) of the chromosome numbers in the Order is appended.