244 



MANUAL OF ZOOLOGY 



usually not developed in the males, are biting or piercing 

 organs, while the basal parts of the labium form a proboscis 

 enclosing a sharp spine developed from a process on the 

 roof of the mouth (hypopharynx). 



In the Lepidoptera, or butterflies and moths, the mandi- 

 bles are aborted in the adult and the maxilla are developed 

 into elongated half-tubes, which are united and form a com- 

 plete tube capable of being coiled up in a spiral manner 

 under the head, the extremity in some cases being provided 

 with hooks or spines for rupturing the nectaries of flowers. 



Fig. 143. 



~sx^ 



-Butterfly (Pieris rapae), with caterpillar and chrysalis stages. 

 (After Riley.) 



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 (not more than five) 

 of short segments, and 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 usually bear each a pair of wings. The wings 

 are thin transparent expansions of the integument sup- 

 ported by a system of branching ribs, called veins, or tier- 



