THE BUTTERFLY. 73 



At the base of the anterior margin of the fore 

 wing is a horny scale, such as occurs in many 

 other insects [see Fig. 72], These scales improp- 

 erly bear different names in different orders, and 

 in butterflies are termed patagia or shoulder lap- 

 pets ; they protect the extreme base of the wing, 

 and being attached to the body only at their front 

 margin, are movable and do not interfere with the 

 free action of the wing ; being covered, like the 

 thorax, with scales and hairs, they are noticeable 

 only when these are removed, appearing in their 

 natural condition to f orm a part of the solid body. 

 Whether they should be considered as an element 

 of the middle thoracic ring, or an appendage to 

 the same, has not been proved ; from analogy 

 with other parts in the abdomen, it seems prob- 

 able that, like the wings, being useful to the in- 

 sect only in its perfect stage, they also are new 

 structures, and not modifications of parts already 

 existing in the caterpillar. 



The only other point of interest in the thorax 

 are the spiracles, of which there is only a single 

 pair, opening upon the scaly membrane at the 

 hind border of the front segment ; as in the 

 earlier stages, spiracles are wanting upon the 

 middle and last segments of the thorax, where 

 the wings occur. We shall again refer to this 

 point. 



About half the bulk of the butterfly's body is 



