Callosobruchus maculatus (Fabricius) develops in the seeds of Vigna unguiculata in the Sahel region of Africa. The reproductive activity of this species and the development of its offspring were studied during the dry season at Ouagadougou and Bobo Dioulasso (Burkina Faso), two zones with different climatic conditions. The length of imaginal life of the females and the developmental time varied with changes in climatic conditions, the lowest values for both parameters being found at the end of the dry season when temperature and humidity increased. In the two zones, variations in the density of the bruchid populations have been studied in experimental stores. The density of the bruchid population was low at the beginning of the study and increased when temperature and humidity rose. The introduction of Dinarmus basalis (Rondani) adults to the stores caused a significant reduction in the numbers of C, maculatus adults. The density of the D. basalis populations was low from December to February and increased when temperatures and then humidity became higher. The increase of the D. basalis population and the rate of parasitism were greater at Bobo Dioulasso than at Ouagadougou. Laboratory studies have demonstrated that fecundity, duration of adult life and developmental times depend on humidity. This study has shown the importance of local climatic conditions on parasitoid reproduction and development and also in the control of bruchid populations in stores.
Inbreeding is said to reduce vigour and fitness. It may also determine how a population responds to selection. Local populations of Callosobruchus maculatus, the cowpea seed beetle, are established annually from small numbers of founders and the species has been distributed to many parts of the world where isolated populations may have been founded by very small numbers of individuals. After more than 20 generations of inbreeding, inbred lines have been shown to diverge from a common ancestral stock in similar directions with respect of some variables such as developmental speed, but haphazardly in respect of other parameters such as male weight. The respective roles of drift and of selection as effective evolutionary forces in inbred lines are discussed in the light of these results. It is argued that some intraspecific differences in C. maculatus may be explained as a product of periodic inbreeding, but that the process does not impair the ability to adapt to local conditions so contributing to the status of the species as a pest of international importance.
The behaviour of insects between making contact with a potential oviposition site and the act of oviposition itself determines the conditions in which their progeny begin development and, in many cases, whether a crop or commodity is damaged. In this paper the behaviour of female cowpea seed beetles, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae), during this period has been examined. The duration of discrete behaviour patterns within this period and the transitional frequencies between them have been used to compare the behaviour of beetles on two different hosts. In a 30‐min period, beetles laid more eggs on mung than adzuki beans and rejected mung as an oviposition site much less frequently. A log‐linear contingency table analysis of the transitional frequencies indicated a highly significant interaction between successive behaviours and between the second of the two behaviours and the host seed, indicating that the sequence of behaviours is partially determined by the host seed. Grooming, departure from the seed and loops in behavioural sequences occur more often on adzuki than mung and are indicative of a less acceptable host. Discriminant analysis showed that the total time spent exhibiting different behaviour patterns was significantly different on the two hosts. Mann–Whitney tests revealed small but significant differences in the mean durations of only three behaviour patterns on the two seed types. Measurement of the duration of each behavioural pattern confirms what can be deduced about host acceptability by observing the simple occurrence of different behavioural patterns and the determination of the frequency of transitions between them. Differences in acceptability were predominantly reflected in the frequency of certain behaviour patterns and of particular transitions from one pattern to another, not in the mean duration of each exhibition of a defined behaviour pattern. It is argued that the utility of measuring the duration of behavioural elements could only be demonstrated because behavioural patterns or categories were precisely defined.
Abstract. The activity of female Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), the cowpea seed beetle, between making contact with a potential host seed and egg deposition is analysed in detail on cowpeas, mung beans and mung beans bearing conspecific eggs.The data differ from previous accounts in that descriptors do not ascribe function (inspection, patrolling, etc.) to the activities but are restricted to observable postures and movements.From the twenty‐four discrete patterns of behaviour, kinetograms are constructed following analysis of a three‐dimensional contingency table in which expected values have been calculated in eight models assuming various considerations of independence, from complete independence of each behavioural element to alternative two‐way interactions among the three variables, viz preceding behaviour, following behaviour, and host.Core transitions were determined by calculation of standardized residuals, by their high conditional probabilities and transitional frequencies.There is a very clear sequence of oviposition behaviour, parts of which are the same on all three hosts.The simplest behavioural sequence was observed on mung beans which was shown to be the most acceptable of the three hosts.The presence of an egg resulted in a diversification of behaviour.The method provides a quantitative method of describing and comparing behavioural sequences and hence a means of determining one aspect of the acceptability of different hosts.Using this method the occurrence of a behavioural sequence has been determined with an objective statistical basis applicable to numerous multitrophic relationships.
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