-aut. 23. BLISTER BEETLE TRICRANL'V. PARKER AND BOVING. 25 



Protliorax, subtrapezoidal, before moult witii posterior margin 

 medially almost effaced. On each side of middle line of tergum with 

 one light brownish, subtriangidar plate, about half as large as ventral 

 side of epicraniiim. Prothorax somewhat longer than and about 

 twice as wide as head. Hypopleural chitinization small and linear. 



Meso- and metathorax, subtrajoezoidal ; in first period of stage 

 somewhat shorter, in last period somewhat longer, than head. Pos- 

 terior width of mesothorax in proportion to its length, as three to 

 one, of metathorax as four to one. Epipleural area large, not dis- 

 tinctly separated from tergum. Hypopleural chitinizations small 

 and linear, same size as in prothorax. Sternal region simple. 



Legs, inserted widely apart; ambulatory type, but small and un- 

 fitted for locomotion. All of same size, about as long as side of 

 head-capsule from base of antenna backwards. Coxa large, coni- 

 cal, with oblique base, about one-third of the length of the entire 

 leg and somewhat longer than the mandible. Trochanter well de- 

 veloj^ed. Femur subcylindrical, a little shorter than coxa, about half 

 as wide as long. Tibia conico-cylindrical, almost as long as femur, 

 but somewhat narrowei-. Tarsus short and claw-shaped. 



Abdominal segments, with dorsal and ventral sides convex; lat- 

 erally with large, but not protruding or ridge-forming epipleural 

 areas; ventro-lateral suture not sharp in the last period of the stage. 

 First to seventl) abdominal segments alike; third and fourth seg- 

 ments somewhat wider than others; abdomen tapering anteriorly, 

 and still more posteriorly toward the terminal complex of the eighth 

 to tenth abdominal segments, which together form a cone of equal 

 length and width. Tenth segment not much shorter than the ninth. 



Anal opening, perpendicular, ventrally bifurcate. 



Spiracles, placed dorsally, annular; one mesothoracic and seven 

 abdominal, extraordinarily large, gradually decreasing somewhat in 

 size posteriorly; seventh abdominal spiracle about half as wnde as 

 the anterior spiracles: eighth abdominal spiracle very minute. 



Differentiating characters. — The fourth instar is known in more 

 M'eloid genera than the third, partly because the third stage has been 

 overlooked or not recognized as a distinct stage, different from the 

 fourth, partly because the cast skin of the fourth instar either is 

 attached to the end of the fifth instar as in Zonahrini, Ejncautini, 

 and Lytini, or partially envelops it, as in the Meloini, or completely 

 surrounds it as in all the Nemognathinae^ and this fifth instar is 

 more easily and frequently found than the previous instars. 



The genera of the subfamily Nemognathinae of which the fourth 

 instar is known are: Hornia, Allendesalazaria, Stenoria, Sitaris, 

 Apaltts, Sitarohrachys^i Leptopalpus^ Zonitis, and Nemognatha. In 

 most of these genera the instar does not need to change from one 



