82 Psyche [June 



labrum are quite turned up and over to form a trough, and the 

 tip has also coalesced. From this stage onward to the hatching 

 of the nymph, the various parts differ little from the adult, in 

 which, however, the lines indicating the egg-burster, discernable 

 since the third day, are not present. The basal portions of the 

 setse in the latter embryonic stages project slightly into the thorax 

 as in the Heteroptera. On account of the comparative shortness 

 of the setae in Siphanta the basal portion is merely curved into 

 the shape of the figure 6, and is nearly all contained within the 

 head. 



Nymph AL Head of Cicada. 



In the nj'mph of Cicada, which appears to be less specialized 

 than Siphanta, we found the relations of the setse to the head- 

 capsule clearly defined, and the key to the head of Siphanta. 



In the head of Cicada there are three longitudinal sulci on each 

 side. The first and most dorsal of these commences near the eye 

 and, gradually deepening, runs anteriorly where it fuses with the 

 lateral edges, and forms the main support of the pharynx. We 

 call this the phar^mgeal sulcus (Fig. 11 phc) and the pillar formed 

 by its junction with the anterior-lateral edges of the pharynx the 

 pharyngeal strut. (Fig. 11, pst). The second commences a little 

 posterior to the pharyngeal sulcus and, rapidly deepening, runs 

 anteriorly to the point of articulation of the mandibles; we call 

 it the mandibular sulcus (Fig. 11, mdc). The third, which we 

 term the maxillary sulcus, divides the maxillary plate from the 

 gular region. It runs round and joins the mandibular sulcus 

 beneath the maxillary plate which projects as a free plate from 

 between these two sulci. By lifting up the maxillary plate the 

 setse can be seen attached to the membrane at the junction of these 

 two sulci. The walls of these sulci, especially in the adult, 

 are closely, applied together and have the appearance of being solid 

 plates projecting into the head and have been so described; they 

 have also been described as the tentorium. That this latter opin- 

 ion is incorrect is seen by the fact that the tentorium exists in its 

 normal condition and is formed by three pairs of invaginations. 

 The largest of these invaginations is in the gular region, at the 

 base of the maxillary sulci, and appears as a part of it; it joins 

 the corresponding invagination from the opposite side and forms 



