58 BRITISH LEPIDOPTERA. 



The activity of the respiratory system of the Lepidoptera may be 

 readily surmised from the rapidity with which they are affected by 

 agents, such as ammonia or chloroform, yet the exact manner in 

 which breathing is carried on is unknown. Rapid movements of 

 contraction and expansion of various parts of the body, accompanied 

 by the opening and shutting of the spiracles, are often observed, and 

 are supposed to be respiratory, but it is generally believed that, al- 

 though the tracheae must supply the tissues with oxygen, they 

 do not carry off the carbonaceous waste from the tissues. Many 

 consider that some of these waste matters are passed from the skin, 

 and this is more probable than any other explanation yet offered. It 

 is well-known that caterpillars, shut up and with insufficient air, 

 throw off waste products most freely from the skin, the process being 

 popularly known as " sweating." Some entomologists consider that 

 the skin is built up from within, and since chitin is composed largely 

 of carbon and nitrogen, it is possible that certain of the waste matters 

 may be used in the formation of chitin, and finally passed off when 

 the larva exuviates or casts its skin. 



The Malpighian tubes, a number of coiled filaments found in the 

 dorsum of the larva, used to be considered analogous with the liver of 

 vertebrates, and were supposed to secrete a substance somewhat 

 analogous with bile. They are now known to be excretory organs, 

 and to remove various compounds from the system. It is not yet 

 known how the tubes are emptied, but the material contained in those 

 of some of the Lasiocampid and Saturniid moths, is supposed to be 

 mixed with the silk of the cocoon, and to be used for the purpose of 

 hardening the latter. It certainly seems to be so used in Malacosoma 

 (Clisiocampa), Eriogaster, etc. The substance excreted is generally in 

 the form of oxalate of lime, or some allied compound. 



Lepidoptera, in common with many other insects, have a very 

 complicated nervous system, which may be conveniently considered as 

 consisting of three divisions : (1) The cephalic system. (2) The 

 ventral or ganglionic chain. (3) The accessory sympathetic system. 

 These divisions are, of course, very intimately connected. 



The cephalic system consists of two masses. One is large, and 

 placed above the oesophagus, and, hence, is termed the supra- 

 oesophageal ganglion ; the other is smaller, and placed below the 

 oesophagus, and, hence, is termed the infra-oesophageal ganglion. 

 These are united with nerve fibres, passing round the oesophagus, and 

 forming what is often termed the oesophageal ring or collar. These 

 cephalic ganglia are often spoken of as the brain, and, in these, the 

 nerves which supply the eyes, antennae and tongue originate. 



The ventral chain consists of a series of ganglia. These are small 

 masses of nerve substance, placed longitudinally along the ventral 

 side of the insect. They are arranged in pairs (theoretically one pair 

 in each segment, although often various pairs of ganglia are united), 

 and the ganglia are connected with the ganglia preceding and suc- 

 ceeding by longitudinal nerve fibres or commissures. From these 

 ganglia the motor nerves of the body are distributed to the muscles 

 in the various parts of the body. In the larva of Tischeria ahgustico- 

 lella, the paired ganglia are very distinct in each of the thoracic seg- 

 ments, and in the abdominal segments 1-6. Scudder says that they 

 are usually found in the lepidopterous larvae as far as the 7th ab- 



