GENERAL CHARACTERS 



8 



nor are they themselves parts of the nervous systems of the insects 

 to which they belong. 



The result of our examination of the wings of buttertlies ami 

 moths has been to justify ihe application of the term Lcpidoptera ; 

 but we must now study other equally important and interestirii,' 

 features of the structure of these insects. First, let us note the 

 general form of the bodj'. 



A cursory glance at this portion of the 

 creature's anatomy will show that it con- 

 sists of three distinct and well-defined 

 parts. In front there is the head, the size 

 of which is somewhat small in proportion. 

 Two very large ej-es make up the greater 

 portion of its bulk. It is remarkable, too, 

 that butterflies possess eyes proportion- 

 ately much larger than those of moths. 

 Now, since butterflies always fly by day, 

 and moths are, generally speaking, noc- 

 turnal insects, we might be led to suppose 

 that the reverse of this arrangement would 

 have suited the creatures better ; for a 

 small eye, we should think, would be able 

 to collect sufficient light in the daytime 

 to form a bright image, and a larger light- 

 receiving area would be necessary dm-ing 

 the darker hours for the same purpose. 

 But it is evident that the sense of vision 

 must depend on other conditions besides 

 the size of the eye ; and as these condi- 

 tions are not understood in relation to the 

 eyes of insects, any attempt at an explana- 

 tion would be (piite useless. 



The eye of a butterfly or moth is worthy 

 of a closer examination, for it is a most beautiful and marvellous 

 structure. The outer globular transparent membrane — the cornea 

 — is divided into a large number of minute polygonal facets, each 

 one of which admits light into a small conical compartment sur- 

 rounded by a coloured membrane, and supplied with a flbre of the 

 nerve of vision (the optic nerve). Hence the ej-e is often spoken of 

 as com]]oun<l. 



If you look closely into the eyes of various butterflies and moths 



Fig. 3. — Body of a But- 

 terfly — Undeb Side. 



1-7, segments of the abdomen ; 

 8, anal extremity ; a, antennis ; 

 b, tarsus : c, tiljia ; d. femur ; 

 p, palpi ; /, head ; (j, tliorax. 



