INTERRELATIONSHIP OF LARVAL DEVELOPMENT, METAMORPHOSIS AND AGE IN A PYRALID LEPIDOPTERAN, GALLERIA MELLONELLA (L), UNDER THE INFLUENCE OF DIETETIC FACTORS

Spontaneous variations occurring in the larval development of a holometabolic insect, Galleria mellonella (L), are indicated, details of the authors' findings are given and a method suited to rearing the insects is suggested. Experimental study carried out on larvae kept in strict isolation shows that qualitative variations in the diet (practically devoid of protides and made up of purified wax) brings about two phases of larval development in Galleria; an initial, or strictly larval, phase and a terminal or pre-imaginal phase. Once the pre-imaginal phase has been reached, the individual pattern of development appears to be fixed, and provided that the energy requirements are met metamorphosis takes place normally. The characteristics of the adult (size and fecundity) are governed by the nutritional conditions for the larvae during this pre-imaginal phase (dwarf adults were obtained with a purified wax diet). The initial, strictly larval phase allows substantial modification of the total life-span of the individual insect, as well as of the number and frequency of moults, to be obtained by means of the diet. Metamorphosis may be prevented (a diet permanently devoid of protides produces prolongation of, and belated death in, the larval state). It may also be merely retarded (by a diet temporarily lacking in protides); finally, larval existence may be almost indefinitely prolonged (by alternating diets), and when a state of suspension is achieved in this way moults occur at a very low frequency. The various experimental cases can only be explained by superimposing on the action of the hormonal factors already known to us as being responsible for moulting the action of humoral factors, which can be demonstrated by altering the diet. These experiments show the problem of the coexistence of hormonal and humoral factors for the control of longevity, development, moulting and metamorphosis in insects.