ART. 23. BLISTER BEETLE TRICEAXL\ PARKER AXD BOVING. 29 



fourth instar. The tip and the condyle slightly harder than the 

 rest, but not well chitinized as in fourth instar; the tip also much 

 shorter and its inner surface less developed than in that instar. 



Maxilla, free, protruding, turgid and plump, about as wide as 

 long (palpus not counted). Stipes divided into a distal and proxi- 

 mal part; the distal part with rounded tieshy setose mala, and short, 

 thick, conical three-jointed palpus. Basal, second, and apical palpal 

 joints somewhat smaller than the corresponding antennal joints, but 

 of same shape and relative proportions; short setae on all joints. 



Submentum, mentum, and stipites labii, with tAvo-jointed labial 

 palps, very similar to the same structures in fourth instar. 



Ligula, absent. 



Thoracic and abdominal segments, similar in size and development 

 to the corresponding features of fifth instar. 



Legs, short, thick, conical, protruding, and immovable; with same 

 general appearance but larger than antennae. Coxa indistinct, flat 

 and wide. Trochanter not developed. Femur rather distincty 

 conico-cylindrical. short, three times as wide as long. Tibia, like 

 femur, rather distinct, subcylindrical, as long as femur, but con- 

 siderabl3' narrower. Tarsus indistinct, ver}- short, apicalh' rounded 

 Avithout claw-like end. 



Spiracles, lateral, circular, of medium size; development and size 

 as in fifth instar; one mesothoracic and seven abdominal pairs pres- 

 ent; seventh abdominal pair someAvhat smaller tlian rest; eighth 

 abdominal pair wanting. 

 Differentiating characters. 



The sixth instar is knoAvn from the same genera of the Xeyno- 

 gnathinae as are the fourth and fifth instars. In all of these 

 genera the sixth instar rests inactiA'e inside the unbroken exuvia of 

 the tAvo preceding instars. In Zonitis and Nemognatha the integu- 

 ment adheres to the inner Avail of the skin of the fifth instar and is 

 not shed by the pupa, but surrounds it couipletely together with 

 the tAvo previous exuvia ; in the other genera it is free, is shed by 

 the pupa, pushed backwards, and found attached to the end of the 

 pupal abdomen. 



C. PUPA. 



The process of the pupation inside a capsule formed by the 

 exuvia of the fourth and fifth larval instars, has been described 

 in Part 1. During the moult, the exuviuni of the sixth instar 

 opens along the back, is slowly moved behind by contractions of 

 the young pupa, and pushed together into a little flat mass or 

 pellicle, which is looseh' attached to the end of the pupa. This 

 pupa is pale yelloAvish, completeh' glabrous, and has a swollen 

 abdomen. It does not difier in any respect from the pupae of 

 20183— 2.1— Pi-oc. X. M. vol. CA 4.3 



