NO. 3 



INSECT HEAD SNODGRASS 



6i 



the two being merely strongly convex sclerites set upon the mem- 

 branous lateral wall of the head, and their cavities are a part of the 

 general head cavity. Only the terminal maxillary lobes and the palpus 

 are free parts of the appendage. The lobes arise from the distal end 

 of the stipes, one, the lacinia (Lc), being internal, the other, the galea 

 (Ga) external. The galea is also anterior to the lacinia (or dorsal 

 to it in insects with the head flattened and held horizontal). The 



KLcd 



Fig. 25. — Maxilla of Periplaneta. 



A, left maxilla, posterior (ventral) surface. B, internal surface of cardo. 

 C, right maxilla, anterior (dorsal) view, showing muscles. 



Cd, cardo; e, articulation of cardo with cranium; fga, flexor of galea; 

 Ucc, cranial flexor of lacinia ; Acs, stipital flexor of lacinia ; ft, f emoro-tibial 

 joint of palpus; Ga, galea; /, promotor of cardo; KLcd, adductor of cardo 

 (origin on tentorium) ; KLst. adductor of stipes (origin on tentorium) ; Lc, 

 lacinia ; O, levator of palpus ; Plf, palpus ; ipip, first segment of palpus ; Q, 

 depressor of palpus; q, submarginal suture (and internal ridge) near inner 

 margin of stipes ; r, internal ridge of cardo ; St, stipes ; T, depressor of fourth 

 segment (tibia) of palpus; V, depressor of fifth segment (tarsus) of palpus. 



galea is usually a soft lobe ; the lacinia is more strongly chitinized, 

 and ends in a strong incisor point provided with one or more apical 

 teeth curved inward. Both lobes are movable on the end of the stipes ; 

 the galea can be deflexed, and the lacinia can be flexed inward. The 

 palpus (Pip) arises from the lateral surface of the stipes, a short 

 distance proximal to the base of the galea. The palpus of the roach is 

 five-segmented. 



The musculature of the maxilla (tig. 25 C) comprises muscles that 

 move the appendage as a whole, and muscles that move the terminal 



