NO. 3 INSECT JIEAD SNOUGKASS 75 



in that the head apophyses (B, HA) upon which the adductor muscles 

 of the appendages arise are still connected with the hypopharynx, 

 whereas in Periplaneta the corresponding endoskeletal arms have lost 

 their primitive sternal connections and have become a part of the 

 tentorium. The adductors of the cardo in Heterojapyx (fig. 30 B, 

 KLcd) are well differentiated from those of the stipes (KLst), and 

 cross obliquely the inner ends of the latter. The promotor of the cardo 

 (/) arises against a median ridge of the dorsal wall of the cranium. 

 The lacinia (Lc), which is mostly covered dorsally by the galea, has a 

 broad flexor arising within the stipes (Acs), and a large cranial muscle 

 {flee) arising against the dorsal cranial ridge (PeR) on the top of the 

 head, and going dorsal to the other muscles of the appendage to be 

 inserted on a slender apodeme from the inner angle of the lacinial 

 base. The galea (Ga) is provided with a single long flexor (figs. 30 B, 

 31 D, fga) arising within the stipes, which splits into two bundles of 

 fibers toward its insertion on the ventral wall of the base of the galea. 

 The palpus (Pip) is reduced and otherwise modified as compared with 

 that of the roach (fig. 25), consisting of only three segments, of 

 which the basal one (figs. 30 A. 31 D, iplp) is much elongate and is 

 united with the outer wall of the base of the galea (Ga). There 

 might be some question as to the homology of this basal region of the 

 palpus of Japyx, but the insertion upon its base of the muscle (OQ) 

 from the stipes, evidently representing the usual pair of palpal muscles, 

 and the origin within it of a muscle (p) going to the distal segment of 

 the palpus identify the part in question as the true basal segment of 

 the palpus. 



The cardo and the stipes of many insects appear externally to be 

 divided into sub-sclerites, but in most such cases it is found that the 

 so-called " sutures " are but the external lines of inflections that have 

 formed internal ridges, the ridges being developed either for giving 

 strength to the sclerite, or to furnish special surfaces for muscle 

 attachment. The cardo of Periplaneta, for example (fig. 2^A,Cd), 

 has a " divided " appearance externally, but when examined from 

 within (B) it is seen that the regions apparent on the surface result 

 from the presence of a strong Y-shaped ridge (r) on the inner wall, 

 which extends distally from the base to reinforce with its diverging 

 arms the extremities of the hinge line with the stipes. This structure 

 of the cardo is characteristic of other orthopteroid insects. Cranipton 

 (1916) distinguishes the area of the cardo between the arms of the 

 ridge as the " veracardo," and calls the rest of the sclerite the " juxta- 

 cardo." The terms may have a descrijjtive convenience, but they 

 are misleading if taken to signify a division of the cardo into two parts. 



