Courtship and Mating in Lariophagus Distinguendus (Först.) Kurdj

COURTSHIP AND MATING IN LARIOPHAGUS DISTINGUENDUS (FÖRST.) KURDJ. (HYMENOPTERA, PTEROMALIDAE) by J. VAN DEN ASSEM (Department of Zoology,University of Leiden, The Netherlands) . I. INTRODUCTION . In all groups of animals which practise a form of copulation, some pattern of exchange of information has been developed to precede copulation proper. Such a pattern can be called courtship. The behaviour involved may be extremely simple or astonishingly complex. Ethologists have always paid much attention to courtship behaviour. This is not merely because of a professional pre-occupation with sex. One of the reasons of this interest certainly is the great diversity in appearance of courtship behaviour, which is the outcome of its development as a system of unambiguous communication between individuals of opposite sex. Courtship behaviour functions to increase the probability of an effective fertilisation, following the coming together of the correct partners at the right moment. If a fertilisation is to be effective, it has to be ensured before that the partners are indeed compatible. This calls for the development of a system of communication that leaves no doubt about the identity and the physiological state of the individuals involved. In insects it is frequently the female 330 partner that is unwilling to mate straight away, but has to be led into a receptive state by some sort of stimulation from the male. The correct partner is able to provide the necessary stimulation at a short term. In a courtship situation females most often appear to be more selec- tive than males. The current explanation of this phenomenon is that they have to, because of their mating frequency. As a rule, male insects show a far greater mating potential than females, which may even restrict copulation to a 'once-in-a-lifetime' occurrence. Hence, mating with the wrong partner would have much more severe con- sequences for a female than for a male (MANNING, 1965). Apart from the functional aspects of courtship is the question of its immediate causation. Most work on the causation of courtship behaviour has been done with vertebrates. The results suggest that such courtship contains elements of agonistic and sexual behaviour in combination with other elements that seem to originate from motivational conflicts. The causation of courtship in insects may prove to be fundamentally different from that in vertebrates, but so far too little work has been done to allow decisive conclusions. The comparative method can be used to obtain some insight in the origin of courtship behaviour, and also in the actual motivational factors which play a role. It seems to me that some hymenopterous groups are rather suitable for such comparative work because of the great diversity of closely related taxa. This paper deals with the reproductive behaviour of Lariophagus distinguendus, a parasite of, among others, the common granary weevil, Sitophilus granarius. Lario?bhagus is rather well known in the entomological literature. The insect is a cosmopolite, and it is of some economic significance as a parasite of an important pest. The frequent interest has led to some synonymy. For reviews the reader is referred to RUSCHKA ( 1921 ), to KASCHEF (1955) and to DE VERE GRAHAM (1969). A number of authors have studied one or more aspects of the behaviour of Lariophagus. They were interested in its interactions with its hosts: the way of searching for a host, the acceptability of different developmental stages of these hosts and the stimuli by which suitable hosts are recognised. Chemical cues seem to be of greatest importance (HASE, 1924; KASCHEF, 1955, 1959, 1963).Theimportanceofacoustical stimuli has been stressed by SMIRNOV et al. (1937). The most acceptable stage of the host seems to be the pre-pupa (KASCHEF, 1954, 1955). KASCHEF'S monograph (1955) contains many data on morphology, development, interactions with a host species (Stegobium), and on several behavioural aspects. .

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