. Animal physiology. Physiology, Comparative. HABITATION OF CADDICE-WORM. 533. 273.—C, Phryganra or Caddice-Fly tube formed by its larva ; B, network at the entrance of the tube. SO as to make a tube (a), in wliicli the animal creeps along the bottom and sides of the brook it inhabits, and sometimes rows itself on the surfcice of the water. AVhen full- grown, the larva attaches its case by threads to some large stone ; and then covers its mouth wdth an open net-work of threads (b), sufficiently close to prevent the entrance of insects, but with meshes permitting the water to pass through. In t
. Animal physiology. Physiology, Comparative. HABITATION OF CADDICE-WORM. 533. 273.—C, Phryganra or Caddice-Fly tube formed by its larva ; B, network at the entrance of the tube. SO as to make a tube (a), in wliicli the animal creeps along the bottom and sides of the brook it inhabits, and sometimes rows itself on the surfcice of the water. AVhen full- grown, the larva attaches its case by threads to some large stone ; and then covers its mouth wdth an open net-work of threads (b), sufficiently close to prevent the entrance of insects, but with meshes permitting the water to pass through. In this way it undergoes its metamor- phosis into the Pupa state; and a short time before its last change it cuts the threads of the network, by means of two hooks with which its head is furnished, and creeps out of the water ; soon after which it changes into the perfect insect. 702. It is scarcely i)ossil.)le to point to any actions better fitted to give an idea of the nature of Instinct, than those which are performed by various Insects when they deposit their eggs. These animals never behold their progeny, and cannot acquire any notion from experience, therefore, of that which their eggs will produce ; nevertheless they have the remarkable habit of placing, in the neighbourhood of each of these bodies, a supply of aliment fitted for the nourishment of the larva that is to proceed from it; and this they do, even when they are themselves living on food of an entirely different nature, such as would not be adapted for the larva. They cannot be guided in such actions by anything like reason, since the data on which alone they could reason correctly are wanting to them; so that they would be led to conclusions altogether erroneous, if they were not prompted by an unerring instinct to adopt the means best adapted for the attainment of the required end. 703. Of this kind of instinct, the Necrophorus (fig. 274), a kind of Beetle not uncommon in our fields, offers a good example. When
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