L'OOPHAGIE DES LARVES DU PREMIER STADE DE CHRYSOPE (NEUROPTERA, CHRYSOPIDAE)

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Abstract
L'oophagie précoce par les jeunes larves de Chrysopa perla dès leur éclosion est étudiée expérimentalement au laboratoire. Les conditions de cette oophagie sont précisées en rapport avec l'âge de l'œuf, l'état physiologique de la larve, son comportement, ainsi qu'avec les facteurs écologiques (température, humidité). La valeur biologique pour la larve cannibale est certaine si l'on considère la durée et les conditions climatiques de sa survie; mais l'état de développement de l'embryon fait varier considérablement ces résultats.Summary: OOPHAGY IN FIRST STAGE CHRYSOPID LARVAE (NEUROPTERA, CHRYSOPIDAE)Some factors concerned in early cannibalism through oophagy, and the biological worth of the latter, have been studied with Chrysopa perla in the laboratory. Eggs offered as prey are differently accepted according to the stage of embryonic development. Before the third day after laying, acceptance is 100%; after the fifth day, refusal is 80%. The hardness of the embryonic membranes, which was measured with tactile needles, is solely responsible for this. It increases over 17 times from the first to the fifth day, then on the last day declines to a little less than 7 times the initial value. Independently of the probability that a newly hatched larva will come upon an egg, the long time during which all the eggs of a given batch are hatching, even taking into account the resting period that follows hatching, always allows cannibalism by means of oophagy. But the act of sucking out the very first prey immobilizes the predatory larva for a rather long time, which diminishes later. Stalked eggs are found by the larvae only about two times out of three during half a day of searching. The protective value of the footstalk varies greatly with temperature and with the dryness of the air. In a compact batch, stalked eggs seldom are eaten. The duration of larval survival after egg‐eating changes with the embryonic stage of the eggs consumed; an egg when first laid is a food of good quality which is in many ways better than an aphid. Ecdysis may take place after three newly laid eggs have been eaten; in the case of a mixed feeding (first with eggs, then aphids) the duration of the first larval instar may be shortened. An egg that contains an embryo is but poor food. Whatever the state of their development, eggs ensure a better resistance to desiccation. Eggs wounded only superficially by the mouthparts of the young larvae do not hatch normally; the secondary mortality resulting from these wounds increases with saturation deficiency.