l6 SlsriTHSONIAN MISCELLANEOUS COLLECTIONS VOL. lO/ 



while the mouth parts and antennae project posteriorly beneath the 

 skin of the head. 



Orthoptcra. — Most of the Orthoptera retain at least a part of the 

 cuticular cleavage line in the adult, though neither in the imago or 

 the nymph do the arms always represent the full length of the exuvial 

 splits that take place at ecdysis. 



In the Mantidae (fig. 4 D) the frontal arms of the cleavage line go 

 dorsal to the paired ocelli, and, in the adult insect, appear to be con- 

 fluent with the temporal sulci {ts) that turn back from them over 

 the top of the head. As already explained, however, this apparent 

 continuity of the cleavage lines with the temporal sulci is due to the 

 invasion of the former, on the inner surface of the head wall (G), by 

 spurs {d) from the temporal ridges (TR). On the head exuviae of 

 a nymphal mantis (E, F) it is seen that the temporal sulci (fs) do 

 not reach the arms of the cleavage line. At ecdysis of the mantid the 

 frontal clefts extend to the compound eyes and cut deeply into the 

 corneae (F, £) as in Forficula (C). The lower halves of the corneae 

 are then pulled downward with the depression of the frontal apotome 

 (F, frapt), and the mouth parts and antennae project posteriorly 

 beneath the head capsule. 



In the Phasmatidae, Blattidae, and Gryllidae, the arms of the 

 cleavage line appear to end at the lateral ocelli. In a nymph of 

 Periplaneta americana undergoing ecdysis (fig. 4H), however, it is 

 to be seen that the frontal splits go below the ocellar spots and proceed 

 to the mesal angles of the antennal fossae, whence they turn upward 

 along the dorsal rims of the fossae to points above the bases of the 

 antennae. The parietal lobes of the head exuviae are then forced to 

 each side by the emerging head of the new instar, producing deep 

 folds through the corneae of the compound eyes, but not splitting 

 them. Finally, the facial region of the slough is turned flat ventrally 

 (I) as in the mantid, forming deep infoldings of the eyes and the 

 genae on each side, the edges of which partially overlap the bases of 

 the antennae. The exuviae of the maxillae and labium are drawn up 

 into deep pockets on the under side of the head. 



In Gryllohlatta, Crampton (1932) shows the cleavage line on the 

 head of a full-grown nymph with the arms going directly to the rims 

 of the antennal fossae, and Walker (1931) indicates the same line 

 very faintly marked on the head of an adult. 



In nymphs of Acrididae the line of the exuvial cleavage is scarcely 

 perceptible, but at ecdysis the thoracic split extends over the top of 

 the head and forks at the upper end of the frontal costa. Duarte 

 (1939) says of Locusta migratoria that the frontal splits of the 



