Understanding of the control of growth in the locust (Locusta migratoria L.) is presented as a problem of the relationship between “nature” as represented by genetic information and “nurture” as represented by the locust's food and by the environmental temperature.
Emphasis is placed on the role of proteins in the translation of the genetic code and on the formation of protein species from genes according to the model given by Jacob & Monod. In insects, neurosecretion may influence protein metabolism at the level of mRNA formation in the nucleus, and it is suggested that the mode of action is suppression of the negative feedback of the metabolite on to its specific gene locus. The release of neurosecretory material is related to food intake, information about which is relayed from stretch receptors in the pharynx, via the frontal ganglion and frontal connectives to the brain. Surgical interference with this pathway leads to a complete cessation of growth in the animal.
Studies on the action of fluctuating temperatures on the growth of the locust also show hormonal involvement. Under certain temperature regimes the corpora cardiaca is empty of neurosecretory material but there is no evidence of failure of its formation. It is thus assumed that it is being secreted and utilized, yet growth is slow or nonexistent. It is suggested that under these conditions protein metabolism is maximally stimulated as different protein species are needed to meet different requirements imposed by the changing environmental temperature.
A model has been constructed which suggests a common basic mechanism to these and other phenomena. The model is formalized by the application of simple Boolean algebra.