1904] McCLENAHAN:— RHYNCOPHOROUS COLEOPTERA. 9I 



II. The Larva. 



The larvae of Balaninus naskus Say vary, considerably in size. The average 

 larva, however, is about 15.^ mm. from tip to tip; measured over the back, as it 

 lies in its ordinary curled position, about 18 mm.; and 4 mm. in diameter. It is 

 uniformly white in color with brown mandibles and an imperfect dorsal prothoracic 

 shield of yellowish chitin. On each side are four rows of very small setae, two on 

 either side of the spiracles. The ventral setae arise from conspicuous prominences. 

 A few scattering ones lie on the under side of the body. 



This larva (Plate VI, fig. 2) is of a very degenerate type. It has no organs 

 except those for feeding. It wholly lacks eyes, antennae and legs. Correlated 

 with the absence of eyes, the brain is destitute of optic lobes. The head is unusu- 

 ally small and the short, and close-set face and mouth parts give no hint of the 

 remarkable extension they will undergo at transformation. 



Mouth Parts. 



Save for a slight reduction in maxillae and lal^ium the mouth parts are much 

 like those of other beetle larvae. The labrum is broadly rounded and supports 

 near its edge ten spines and on the dorsal surface two or three pairs additional. 

 At the middle of its posterior edge it is slightly produced backward into the clypeus. 

 The mandibles (Plate VIII, fig. 12 md.) are somewhat triangular in outline with 

 an ill-defined tooth upon the inner edge and two larger ones at the tip. They are 

 moved by two large muscles (Plate VIII, fig. 12 ab. mi^ and ad. m.^) which occupy 

 the greater part of the head. The adductor is {ad. m.^) larger and is attached 

 through a stout tendon to the inner basal angle of the mandible. It is made up 

 of numerous straight fibres, some of which arise from the wall of the head, others 

 from a median dorsal chitinous endoskeletal ridge. The fibers of the abductor 

 {ab. iir.) are all attached to the latero-ventral wall of the epicranium. These unite 

 into a short tendon which connects with the outer basal angle of the mandible. 



Maxillae (Plate VIII, fig. 12, mx.) are comparatively simple. Cardo and 

 stipes meet at a right angle. The latter is fused \vith the lacinia, which is armed 

 on its edge with a row of ten spines. The galea is two jointed with four minute 

 prominences on its tip. Palpus is wanting. Three sets of muscles serve to move 

 the maxilla — two adductor and one abductor. The larger adductor (Plate VIII, 

 fig. 12, ad. m}') is inserted near the tip of the lacinia. It is a compact band of 

 fibers and takes its origin at the rear of the head. The lesser adductor (Plate 

 VIII, fig. 12, ad. m.-) springs from the ventral part of the tentorium and is inserted 



