l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



cleavage line reach the antennary sockets, but in Dissosteira and 

 Melanoplus (fig. 4 J) the median cleft opens above the frontal costa 

 in two short, wide lateral arms ending between the paired ocelli and 

 the antennal sockets. 



Hemiptera. — The line of cuticular cleavage on the head presents 

 some interesting variations in this order. Though the frontal arms 

 always go anterior to the eyes, and, when sufficiently extended, laterad 

 of the antennae, the coronal stem is of variable length, and may be 

 entirely absent. Many examples of the course of the "epicranial 

 suture" in the Homoptera and the Heteroptera are given by Spooner 

 (1938) in his comparative study of the head capsule of the Hemiptera. 

 The nymphs of such species as Ceresa sp. (Membracidae), Lyperonia 

 qnadrangularis (Cercopidae), Ranatra amcricana and Nepa apiculata 

 (Nepidae), Gerris marginatus (Gerridae), Lam pr acanthus sp. (Sal- 

 didae), Alydus sp. (Coreidae), and others are shown to have a typical 

 Y-line of exuvial cleavage. In some others, however, the coronal 

 stem is short and the frontal arms branch from it far back on the 

 head, as illustrated by Spooner in Cimex lectiUarius (Cimicidae) and 

 Ischnodemus f aliens (Lygaeidae), and as shown in the present paper 

 in Oncopeltus fasciatus (Lygaeidae) (fig. 6 A) and in Cimex lectu- 

 larius (B). The ecdysial splits in Cimex follow the arms of the 

 cleavage line and extend to the anterior dorsal angles of the eyes. 

 The large frontoclypeal apotome of the exuviae (C, frcapt) is then 

 turned forward and flat downward, with the beak directed posteriorly, 

 while the narrow parietal lobes {Prtl) carrying the eyes and the 

 antennae are spread out laterally. 



Finally, in the Pentatomidae, as seen in Brochymena sp. figured 

 by Spooner, and in Acrosternum hilare and Mergantia Jiistrionica 

 here illustrated (fig. 6 D, E), the coronal line is absent, and the 

 frontal lines arise widely separated on the occipital margin of the 

 cranium. At ecdysis of such species, the frontal splits, branching 

 directly from the median cleft of the thorax and neck (fig. 6 D), cut 

 off small, lateral parietal triangles of the vertex (Prtl) bearing the 

 compound eyes, and leave the median part of the cranial margin 

 unbroken. 



The frontal arms of the cleavage line also are variable in length and 

 position. They may reach to points between the eyes and the antennae 

 (fig. 5 A; fig. 6 A), but more often they do not extend beyond the 

 eyes (fig. 5 D, E, F ; fig. 6 B, E) . When the coronal stem is relatively 

 long the arms may diverge forward on the top of the head, as in the 

 nymphal cicada (fig. 5 A), in which at ecdysis the frontal splits cut out 

 a small triangular frons (B). In the Fulgoroidea, however, which 



