The locust plague and its suppression / by Æneas Munro.

  • Munro, Aeneas.
Date:
[1899]
Catalogue details

Licence: Public Domain Mark

Credit: The locust plague and its suppression / by Æneas Munro. Source: Wellcome Collection.

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    formed can be seen to lie within its shell or lining, as in Fig. 8, c. The antennse come down over the face and lie in close relation to the mouth—the parts of which are really well developed. The head is bent so that the mouth rests on the trunk or thorax. The legs are folded upon the breast. There is no difficulty in discovering the strong terminal hooks on the hind legs—they reach as far as the middle of the sternum or trunk. Towards maturity there is a continued series of contractions and expansions of the several parts of the embryo. With these the membrane gradually gives way at the points d and e, and very often there is a transverse slit as well. The membrane tearing in this way, the young embryo gradually manages to dis- encumber himself from his imprisoned position, and effects his escape through the channel already indicated without disturbing the other eggs, the embryos of which in turn and almost at the same time follow suit. 123. Casting- the slough.—As soon as the little insect escapes, its first duty is to cast off a pellicle called, as we have seen, the amnion, which completely surrounds every part of it. This it does almost immediately, and then it is free to move about actively and eat. This amniotic covering is highly useful to the animal as long as it is under ground. It preserves it in some way, and seems necessary for its safety. The amniotic covering does not interfere with its forcing or pushing power to get free and “ into the open,” for sometimes its passage through the channel already referred to may be interfered with, and it can, under certain favourable circumstances, make its way through the loose earth to the top, but when it gets to the air the covering seems to be then quite unnecessary and an encumbrance to it. To enable it to be perfectly free, it sheds it off at once. This amniotic covering is common to most hymenopterous, dipterous, caleopterous, hemipterous, orthopterous, and neuropterous insects. When the covering is accidentally removed, while the insects are still under ground, they seem to lose much of their forcing power upward; with it still intact, they can do much to effect their escape; without it, they seem sometimes much more, if not absolutely, powerless. They instinctively know the nearest way to the free surface and open air, a fact which has been demonstrated by many decisive experiments. We then see our little creature as in the following Fig. 9, 1. In this figure may be noticed the varying stages of growtji up till the period of last moulting—2, 3, 4, and 5. LARVAE AND LARVAL LIFE—THE “ARMY” 124. Metamorphosis.—We have now to consider the locust in its larval stage, in which it is found to be most destructive to the crops
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