NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS 5 



as contended by Cook (1944a), though some writers have regarded 

 it as a "preclypeus." The groove behind it (A, els) then is the 

 clypeolabral sulcus. The large central area of the head is bounded by 

 lateral lines {CL) that diverge forward from a very short occipital 

 cleft and become continuous with the clypeolabral sulcus. These 

 lines, commonly called "frontal sutures," are merely lines of weakness 



Fig. 1. — The larval head, dorsal and lateral. 



A, Aedes aegypti. B, Culex sp. C, Anopheles quadrimaculatus. D, Toxo- 

 rhynchites rutilns. E, Culex sp., lateral. F, Anopheles farauti, head exuviae. 



Ant, antenna ; Apt, cephalic apotome ; CL, cleavage line ; els, clypeolabral 

 sulcus ; E, compound eye ; Ge, gena ; Hstm, hypostomium ; Lm, labrum ; Md, 

 mandible ; Mx, maxilla ; O, group of larval simple eyes ; Pge, postgena. 



in the cuticle where the latter will split at ecdysis (F, CL) to allow 

 the emergence of the next instar, and are best termed the cephalic 

 cleavage lines. In most young insects the cleavage lines take the form 

 of a Y, which has been known as the "epicranial suture." In the 

 mosquito larva the stem of the Y is the short occipital cleft. The 

 frontal arms follow such very different courses in different insects 

 that they can have no morphological significance (see DuPorte, 1946; 

 Snodgrass, 1947), and hence do not define any specific part of the 



