242 MANUAL OF ZOOLOGY SECT. 



in a spiral manner under the head, the extremity being 

 provided with hooks or spines for rupturing the nectaries of 

 flowers. 



Each of the three segments of the thorax always bears a 

 pair of jointed legs which do not present such marked 

 modifications as the appendages of the head. The terminal 

 part (tarsus} is made up of a number of short segments, and 



FIG. 133. Butterfly (Pieris), with caterpillar and chrysalis stages. 

 (Aft :r Guerin and Percheron.) 



ends in a pair of claws, often with an adhesive pad or 

 sucking disc between them. 



In addition to the legs, the second and third segments of 

 the thorax may each bear a pair of wings. The wings are 

 thin transparent expansions of the integument, supported by 

 a system of branching ribs or nervures. In most of the 

 Butterflies and Moths (Fig. 133) the wings are opaque, 

 owing to their being covered with numerous overlapping 



