The Growth of Blackbeetles and of Cockroaches on Artificial and on Incomplete Diets. Part I

Abstract

1. The normal development cycle at 25° of the blackbeetle lasts about 12 months, that of the cockroach about 3 months, so that in comparing the velocity of growth of these insects the ratio 4 : 1 may be taken (1 month is equivalent to 1 week). 2. During approximately one-third of these periods the insects grow equally rapidly on synthetic as on normal diets. 3. The entire development cycle of the blackbeetle could not be completed on a synthetic diet. The larvae attain barely one-third of the normal weight during the normal post-embryonic development period, after which they die, without, however, losing weight to any great extent. 4. Blackbeetle larvae put on synthetic diets half-way through the growth period can attain sexual maturity. 5. The cockroach is able to complete its entire development cycle on a synthetic diet, even when the only nitrogenous constituent is glycine. 6. The symptoms of avitaminosis, which appear after the above-stated time, are lack of mobility, the appearance of a matt surface of the chitin envelope; should sexual maturity be attained, small dimensions and infertility are characteristic symptoms. 7. Ovalbumin may be replaced by biologically deficient proteins such as gelatin, or even by glycine, without in any way affecting the character of growth. 8. By diminishing the percentage nitrogen content in diets the rate of growth is distinctly diminished, but at the same time the period of its duration is prolonged. 9. Blackbeetles and cockroaches are exceptionally resistant to the absence of nitrogenous constituents in their food, being able to maintain their body-weight over periods of time equal in length to that of the entire normal post-embryonic cycle. 10. Even after prolonged inhibition of growth, the administration of a normal diet allows these animals to resume growth and attain sexual maturity, including the production of normal young. 11. The rate of growth of insects which have been given normal food after long periods of inhibition of growth is independent of the actual age of the insect, and corresponds to that which the animal possessed at the commencement of the period of inhibition. 12. These insects do not survive long if fed upon exclusively protein diets, in the absence of carbohydrates. 13. The addition of small quantities of butter, yeast, or vitamin B extracts to synthetic and complete diets does not lead to any enhancement of growth.