24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I07 



that the clypeus of Ilacinalofnnus, in the course of its posterior ex- 

 tension on the head, "has taken over the muscle origins that normally 

 are found on the antennal segment." Why such an unnecessary and 

 confusing interpretation should be invoked is not clear to the writer ; 

 it is scarcely to be credited that these two genera of Anoplura should 

 dilTer so radically in the head structure when they appear to differ 

 only in unessential ways. However, it should be noted that Stojano- 

 vich, earlier in his paper, says his interpretation is according to the 

 "dictum of Ferris." 



On the head of a young elephant louse, Haematomyzus clephantis 

 Piaget, Weber (1939, 1939a) has shown that there is present a typical 

 Y-shaped cleavage line, the frontal arms of which extend forward 

 mesad of the antennae as in Anoplura. At ecdysis (fig. 7 E) the 

 cuticle splits along the arms and there is cut out a triangular frontal 

 apotome (frapt) in continuity with the dorsal wall of the elongate 

 snout. 



Coleoptera. — The larvae of beetles are of particular interest in a 

 study of the lines of ecdysis on the head, inasmuch as they exhibit a 

 transition in the position of the frontal arms from that in which the 

 latter are called "postfrontal sutures" to that in which they become 

 "frontal sutures," or, according to Cook (1943), the "clypeofrontal 

 suture." A review of the many figures of heads of coleopterous larvae 

 given by Boving and Craighead (1931) will show that in the majority 

 of species illustrated the frontal arms of the cleavage line go either 

 laterad of the antennae, or directly to the antennal fossae, but that in 

 a few cases, as seen in Dermestes and Eurypcpla, they run distinctly 

 mesad of the antennae. The last condition, judging from the illus- 

 trations of Hayes (1929), evidently prevails in the larvae of 

 Scarabaeoidea, though in this group the frontal lines may go also 

 either to the antennal fossae, or laterad of them. 



A few examples of the three courses taken by the arms of the 

 cleavage line in coleopterous larvae are shown in figure 8 of the 

 present paper. On the heads of Trichodesma gibbosa (B), Crioceris 

 asparagi (C), and Leptinotarsa decimlineata (G) the arms end 

 laterad of (or posterior to) the antennae; in the larvae of Dytiscus 

 (A), Chalcophora (F), and Hydrophilus (I) they go directly to the 

 antennal fossae, in Dynastes tityiis (D) and Alans oculatns (E) they 

 run mesad of the antennae. It is clear, then, that in the Coleoptera 

 there can be no distinction between "postfrontal sutures" and "frontal 

 sutures" ; there is here only a variation in the course taken by the 

 arms of the exuvial cleavage line on the head. On the facial region 

 embraced by the frontal arms (fig. 8 A) are attached the muscles of 



