2 PROC. ENT. SOC. WASH., VOL. 23, NO. .1, JAN., 1921 



tects the rear side of the setal bases. Behind this is the long 

 labium (LV) which encloses .the setae within a groove along its 

 front surface. Sclented is hidden at its lower end between the 

 clypeus (Clp) and the lobe b of sclerite B. The parts are all 

 tightly compressed and difficult to study in the mature con- 

 dition. 



Figure 5 is the head of an adult cicada just as it emerges from 

 the pupal skin. The general shape is very different from that ^ 

 of the fully matured insect (fig. 4). All the parts are soft and ' 

 stand apart from one another in a way that shows much more 

 of the true anatomical structure. Especially is it to be noted 

 that sclerite A is prolonged downward in a large appendicular 

 structure ()> which scarcely shows at all in the normal mature 

 head. The bases of the setae (Set) are here exposed behind a, 

 disappearing entad to the sclerite B. 



Figure 6 is the head of an imago toward the end of emergence 

 from the pupal skin. The parts have assumed more of the 

 adult form, but are still soft and easily separated as shown in 

 this drawing. Here we get a very different idea of the form 

 and relationships of the mouth parts from that given by the 

 hardened and consolidated mature head (fig. 4). We are at 

 once struck by the resemblance to the mutilated Locustid 

 head (fig. 3). Minus setae, the cicada might be an Orthopteron 

 minus mandibles and maxillae. The clypeus and labrum hang 

 down in front of the mouth (Mth) the same in each. Behind the 

 mouth is a median hypopharynx (Hphy) connected on each side 

 by a flaring membranous wing (a) with the lateral wall of the 

 head (or would be so connected in the Locustid if the hole where 

 the mandible was attached were closed over). The labium 

 (Lb) is suspended from the neck membrane (mb). The lateral 

 head sclerite A is separated from the front by a suture forming 

 a high ridge on the inside of the head, which contributes to the 

 support of the pharynx. But the suture continues upward 

 before the base of the antenna and is continuous with the one 

 from the other side over the upper end of the front. While in 

 this respect it differs from the frontogenal suture of the grass- 

 hopper, it resembles that in the cockroach and other insects 

 where the front forms a distinct facial plate. The outer surface 

 of plate A is minutely but conspicuously punctate in transverse, 

 semi-spiral rugae, and in certain lights has a bright silvery 

 color. The lower posterior part bears a prominent clump of 

 long hairs. The lower edge of the plate appears to be continu- 

 ous with the hypopharynx below, but internally it is separated 

 from the latter by a strong ridge. Separating plate A from B is 

 a deep membranous groove with a thin chitinous bar lying along 

 the entire length of its floor and continuous below with the base 

 of the first seta. This bar will be more fully described in con- 

 nection with figures 13 and 14. 



