LEPIDOPTERA. 



The last of the orders of insects to appear on earth is the one comprising 

 the moths and butterflies, these latter developing simultaneously with flower- 

 ing plants and are generally conceded to be the most beautiful members of 

 the class. The beauty of coloring is due to pigment in the scales which 

 cover the body and which are developed to a degree not found in any other 

 order. The pattern is always in mosaic the units of which are so small as 

 rarely to be seen except under the microscope. The distinction between 

 species is almost invariably based on the color pattern. Specimens that 

 are battered and have lost a considerable portion of their scales therefore 



^^ 



Figure 14. Diagram sliowing the flight of a butterfly, 

 become often quite unidentifiable. 



The most important characters for the classification of these insects are 

 afforded by the venation of the wings. This is often quite hard to make out 

 however because of the scales and can be best studied by bleaching the 

 wings (see appendix.) Most of the features can generally be determined 

 by examining the wings from beneath. The commonest nomenclature for 

 the veins is to number them in order from behind forward using la. and lb. 

 when there are two veins behind the large cell instead of one as is usual. 



A plan of wing formulae has been devised, based on the common system 

 of nomenclature but applying the numbers to the connecting veins or bars in- 

 stead of those proceeding to the margin; bar 2 being between veins 1 and 2. 

 When veins fork from a common stem it is indicated by an * thus 8* is the 

 common stem of 7 and 8. The formula consists of a list of the bars 



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