26 



BRITISH BUTTERFLIES. 



have already dealt with the internal anatomy of a lepidopterous 

 larva at length (Nat. Hist. Brit. Lep., pp. 54 et seq.), and, since that of 

 butterflies does not differ, in any of its essential features, from that of 

 other lepidoptera, we shall not do more here than repeat a few of the 

 salient facts, which may be considered under the following heads : — 



(1) The muscular system: The voluntary muscular system of the 

 larva, is that by means of which it is enabled to move about in order to 

 obtain its food. The muscular fibres are usually arranged as flat 

 ribbons or conical bundles, the latter making up almost the whole 

 structure of the head, and are attached to the head walls, stretching to 

 the mandibles, labium, labrum, etc. A series of contiguous muscular 

 cords, or bands of longitudinal muscular fibres, run from one end of the 

 body to the other on each side, just under the skin, between the 

 spiracular line and the venter of the body ; other longitudinal muscular 

 bands run above the spiracles; a transverse muscular belt encircles 

 the body at the front of each segment, whilst oblique transverse 

 muscular bands run from the front of each segment, and are attached 

 to the medioventral line further back in the segment. Besides these, 

 complicated muscular systems bring about the movements of the legs 

 and prolegs. The involuntary muscular system is principally connected 

 with the digestive and the circulatory organs. The oesophagus is 

 provided with fine longitudinal, and with less well-developed transverse 

 encircling, bands of muscular fibre. The inner coat of the stomach 

 is enclosed in delicate strips of muscular fibre crossing each other 

 diagonally, whilst longitudinal muscles run throughout its length, and 

 the well-developed encircling muscles are similar to those of the 

 oesophagus. The arrangement of the muscular tissue in the intestines, 

 is very similar to that of the rest of the alimentary canal, only the 

 longitudinal bands are often thick and glistening, whilst near where 

 the small intestine joins the stomach, the walls are plentifully supplied 

 with short longitudinal muscles ; the diagonal bands and encircling 

 muscles found in the stomach also have their representatives here. 

 The alimentary canal is held in its place by a series of muscular bands 

 attached to the body wall, one set passing round that portion of the 

 intestine where it is connected with the stomach, another set being 

 attached to, and supporting, the posterior end of the small intestine, 

 these muscles stretching horizontally from the middle of one side of 

 the 8th abdominal segment to the opposite side. 



(2) The alimentary system : The mouth opens into a short gullet, 

 and this in turn expands into a crop and gizzard, before it extends into 

 a somewhat wider sac or stomach, which in its turn narrows into 

 the intestine and ends at the anus. The nutritious parts of the 

 food when dissolved are absorbed almost directly into the blood. A 

 number of long tubules pass into the oesophagus and appear to 

 represent the salivary glands of the higher animals, a fluid being- 

 discharged which is swallowed with the food ; the fluid dissolves 

 certain parts of the food, fitting it to soak through the walls of the 

 alimentary canal so that it can enter into the system. The crop is a 

 sort of food-receptacle, from which the food is passed on to the gizzard, 

 provided with somewhat hard plates for the grinding up of the food, 

 the latter being then passed into the stomach, the walls of which 

 secrete another fluid that renders still more of the food soluble, this 

 part being then readily absorbed by the walls of the stomach and 



