ART. 23. BLISTER BEETLE TRICRANIA PARKER AND BOVING. 23 



The anatomical details of the head and the rest of the body are 

 similar to those of the following fourth larval instar, only smaller. 

 To avoid identical descriptions of these details in the two instars 

 they will be recorded only for the fourth larval instar in which they 

 are more easily seen and investigated. 



Differentiating characters. — The third instar in the Nemognathinae 

 has been recognized by very few authors as representing a definite 

 stage. Cros, however, has recorded it in most of the genera of the 

 subfamily and Beauregard '^ has given a rather full description of 

 it in Sitains tnuralis Foerster. In all the genera it seems to be iden- 

 tical; not a single distinguishing difference has been found, be it in 

 habits, size, or shape. 



FOURTH LARVAL INSTAR. 

 Figs. 10, 15, 16, 30, 31. 



Length of larva, immediately after third moult, about 7 mm.; 

 before fourth moult, about 12 mm. Width, after third moult, about 

 S mm ; before fourth moult, about 5 mm. 



Color, pale cream ; chitinizations light brownish. 



Setae, fine and short on head-parts and legs ; body densely set with 

 fine asperities (fig. 10). 



Body, soft, fusiform-ovate, with both dorsal and ventral surfaces 

 convex. Epipleural areas large, but not forming a swollen lateral 

 ridge. Prothorax, dorsally slightly longer than either of the two 

 other thoracic segments and carrying a pair of light brownish 

 chitinous patches corresponding to a tergal shield. 



Head, seminutant, extended, with head capsule and appendices 

 thinly chitinized, but slightly thicker than in third instar. 



Head capsule, dorsally about 1 mm. long; length and width almost 

 equal; developed as in third instar; dorsal and ventral surfaces 

 slightly convex and smooth. 



Frons, indistinct; laterally fused with epicranium, anteriorly with 

 clypeus. 



Labrum, rather short and broad; inmaovable, posteriorly distinct, 

 but almost fused with clypeus. Antennae, maxillary palps and dis- 

 tal part of mandibles projecting in front of its anterior margin. 

 Setae short, mostly set along the free anterior margin. 



Epicranial halves, fused dorsally, no median epicranial suture; 

 antennal and mandibular foramina combined, about one-third the 

 length of cranium from the mandibular condyle. 



Hypostomal margin between mandibular condyle and posterior 

 end of cardo, oblique and very concave, half as long as side of cra- 



' Insectes vesicants, p. 341. 



