1. Calliphora erythrocephala females will live on a sugar diet but will not reproduce unless protein-containing substances are also ingested. If fed protein without carbohydrate, they die.
2. Isolated females were allowed to select from a carbohydrate (sucrose) solution and from a protein-containing solution (Marmite yeast extract in milk) which were contained in identical capillary tubes. The total volume of food ingested each day over a complete reproductive cycle was found to be fairly constant. Within this total, however, ‘protein’ and carbohydrate were selected in quantities which varied with different phases of the reproductive cycle. Thus during the early stages of egg growth, ‘protein’ was ingested in relatively large quantities, while during yolk formation ‘protein’ ingestion declined. Carbohydrate consumption, on the other hand, was relatively low during the early stages but increased during yolk formation. At oviposition the cycles started again.
3. Carbohydrate ingestion of non-reproducing females (fed on sugar solution only) remained at a constantly low level.
4. Selective feeding did not appear to be influenced by mating.
5. Females were found to accept courting males on the day of the first oviposition but not before. This, of course, necessitated a mixed diet of carbohydrate and ‘protein’.
The relationship between plasma steroid hormone concentrations and the reproductive cycle in the Northern Pacific rattlesnake, Crotalus oreganus