Page:The Effect of External Influences upon Development.djvu/35

Rh nourishment does not induce any degeneration of the ovaries of insects.

In many respects flies (Diptera) resemble bees from a biological point of view: they develop from footless maggots, which live in the midst of suitable nourishment and absorb food almost without interruption. They grow rapidly, and after a short rest in the pupal stage develop into the perfect insect and reproduce abundantly soon afterwards. I reared large numbers of the eggs of a female blow-fly (Musca vomitoria) (see Note IX, p. 61), after separating them into two lots, one of which was uninterruptedly supplied with rich food, while the other was most sparingly fed. In the latter case the larvae were from time to time removed from the flesh into which they had bored and left for a number of hours without food. These larvae grew slowly, and all remained more or less noticeably small. But in point of time their development was not delayed: they underwent metamorphosis simultaneously with the normally fed larvae, only a few of them being one day later. In both cases the larval period lasted from nine to ten days and the pupal stage for from twenty-eight to twenty-nine days. Almost simultaneously all of the several hundreds of flies escaped from the pupa; and from that stage onwards they were kept in large airy cages exposed to the sun, and were well supplied with food (see Note X, p. 62).

Now if the reproductive organs had remained rudimentary in consequence of the poor nourishment, this would necessarily have become apparent by the ill-fed