Difficulties and Successes in the Mass Rearing of Insects in the Laboratory, and the Possibility of Autocidal Control of some Harmful Species

The practical development of the sterile-male release technique, as indeed of all methods of autocidal control of harmful insects, is limited by the difficulties of mass rearing in artificial conditions. However, analysis of cases of the successful solution of this problem for a number of types of Diptera, Lepidoptera and Orthoptera gives an indication of possible ways of setting up large-scale rearing of the insects required. The most difficult problem, that of ensuring a suitable food supply for the insects at any time of the year, is being successfully overcome as a result of the progress made in producing synthetic and semi- synthetic nutrient media, which have been developed both for semi-saprophytic and for herbivorous and predacious species. The choice of recipes for such nutrients is determined by correct selection of the necessary ingredients, above all vitamins, free amino acids and sterols; the proper quantitative proportion between these substances and between the basic components of the food — proteins, fats and hydrocarbons — is of the greatest importance. The amount of work involved in insect rearing depends on what means are used for sterilizing the containers and for preventing the nutrient medium from decaying. One way in which these problems have been solved is by the development of a dried nutrient medium in powder form; this has been successfully used for rearing the migratory locust in the USSR. For a number of harmful species of Lepidoptera, it has been shown possible to rear the insects in a closed, sealed container. In this case a supply of nutrient medium is provided adequate to ensure the insects' development from, the time the eggs or caterpillars are deposited until the imago of the new generation emerges. This approach greatly simplifies the whole process of mass rearing. Many species of insects can be reared on grain or plant seeds which are less subject to decay during prolonged storage. Another important problem is that of developing ways of overcoming the diapause in laboratory populations in order to ensure continuous rearing. This can be done either by reactivating the insects by temperature changes or by instituting a period of illumination which prevents die diapause from starting. A further possible method is that of selecting and crossing diapausing and non-diapausing strains of a given species. A number of species of Orthoptera having a fairly wide natural habitat have been used to show the possibility of autocidal control by adding to a natural population which normally has a diapause specimens of a non-diapausing population from other parts of the habitat. This possibility has been demonstrated for the cricket Teleogryllus corn modus Walk, in Australia and for sub-species of Locusta migratoria L. in the Old World. The development of this form of autocidal control of insects merits close attention. The work reported is devoted mainly to developing methods of autocidal control and techniques for mass laborarory breeding of such harmful species as Carpocapsa pomonella L., Eurygaster integriceps Put, and Locusta migratoria L. (author)