54 BRITISH LEPIDOPTERA. 



the larval ocelli are descended from compound eyes, or are per- 

 sistent from the embryonic form of compound eye, is undoubted. 

 They often occupy a definite tract on the head, which probably repre- 

 sents the area of the compound eye, of which some ocelli only are 

 developed (MI litt.). 



There has not, we believe, as yet, been any attempt to locate an 

 organ of hearing in the larvae of Lepidoptera, although various authors 

 have done so in the imago. Swinton summarises (Ent. Mo. May., 

 xiv., p. 121) the various notes that have appeared on the aural apparatus 

 of Lepidoptera. There is direct evidence that some larvae, at least, 

 show considerable sensitiveness to sound waves. We have noticed 

 that larvae of many species Aglais urticae. Callimorpha dominula, 

 Xenieophila plantaginis, and Lasiocampa querciis, among others throw 

 their bodies violently from side to side, if one speaks in a loud tone, 

 when in their vicinity. 



CHAPTER VI. 



THE INTERNAL STRUCTURE OF THE LE PIDOPTE RO U S LARVA. 



THE external characters of the lepidopterous larva are, owing to the 

 division of the body into segments, each with its own special organs 

 and appendages, easily described, and the position of these structures 

 located. The location of the internal organs is, however, more 

 difficult, for they are not restricted to certain segments, but run longi- 

 tudinally through the body, frequently extending from the thorax 

 forward into the head, or backward into the abdomen. It is necessary, 

 therefore, in dealing with the internal organs, to consider each separately, 

 both as regards its position and function. 



The movements of the body are of the first importance, and we 

 find that larvae have undergone great modifications in order to 

 enable them to vary their movements according to their needs. Move- 

 ment is dependent upon the muscular system, and by the muscles, 

 then, the changes that take place in the external framework and 

 appendages are brought about. The nutrition of the various parts is 

 carried on by food, and to understand this we must study the digestive 

 system. The absorption of the digested food into the blood and its 

 carriage to all parts of the body necessitate a circulatory system, 

 whilst the oxygenation of the blood introduces us to the respiratory 

 system. This latter is so intimately connected with the excretion of 

 waste, that one is insensibly led to consider the excretory system, whilst 

 the organs, by which the whole of these various systems are governed, 

 comprise what is known as the nervous system, and this has to be 

 considered both in its relation to volition and sensation. 



These various systems comprise, then, the different organs (and 

 their functions), by means of which the life of an insect is carried on, 

 and their external results, as exemplified by their movements, etc., are 

 the outward sign of their vitality. The reproductive system, which is 

 not, however, matured in the larval stage, must take the highest 

 place in relation to the continued life of the species. Closely related, 



