22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. lO/ 



cleft, but the adult emerges from a T-shaped dorsal opening formed 

 by a median split through the cephalothoracic region and a transverse 

 cleft between the thorax and the abdomen (see Weber, 1931, figs. 

 20, 21). 



Anoplura. — The exuvial cleavage line on the head of the sucking 

 lice is typically Y-shaped (fig. 7 A, C, D), with some variation in the 

 length of the coronal stem according to the length of the head. At 

 ecdysis, the clefts along the frontal anns go mesad of the antennae 

 and thus take a course characteristic of holometabolous larvae, but 

 which has not been observed to occur in other ametabolous or hemime- 

 tabolous insects. 



In Pediculus hunianus corporis the cleavage line is not visible on 

 the head of younger nymphs; in later instars and in the adult it is 

 present but very faintly marked, and appears as illustrated by 

 Stojanovich (1945) in the adult (fig. 7C). In mature nymphs evi- 

 dently just before emergence of the imago, however, the cleavage 

 line is a pale, distinctly double-edged tract of the head cuticle (A), 

 and it may now be observed that the frontal arms extend to the basal 

 membranes of the antennae. At ecdysis the splits along the arms 

 are farther extended mesad of the antennae to points {x, x) at the 

 sides of the conical fore part of the head. The discarded exuviae 

 have the frontal apotome (B, frapt) turned forward on the trans- 

 verse axis between the ends of the frontal clefts {x, x), together 

 with the snoutlike cone of the head, while the parietal parts of the 

 cuticle are spread out laterally, and in a ventral view (B) are seen to 

 carry the eyes and the antennae. 



In the lengthened head of Haeniatopinus suis, as shown by Sto- 

 janovich (fig. 7 D), the coronal stem of the cleavage line is relatively 

 long, but the arms go mesad of the antennae to points anterior to the 

 antennal bases. The frontal lines of cleavage are therefore the same 

 in both Haematopinns and Pediculus, though in the latter the full 

 length of the clefts is not evident until the ecdysial splits are formed. 



The distribution of muscle attachments on the frontoclypeal region 

 of the anopluran head is shown by Stojanovich in several species, 

 including Pediculus humanus (fig. 7 C) and Haeniatopinus suis (D). 

 It is to be seen that these muscles include, as in other insects, the 

 cibarial dilators (dlcb) and the muscles of the labrum, hypopharynx, 

 and pharynx, and in addition the antennal muscles. In Pedictdus 

 (A, C) a weakly sclerotized band of the cuticle crosses the head 

 between the antennal bases, and appears to separate approximately 

 the clypeal region from the frontal region, but it is questionable if it 

 represents the epistomal sulcus of other insects. As between Pediculus 



