1918] Thoracic Sclerites of Ilemiptera 233 



dorsad nearly to the tip of the abdomen, terminating in a 

 point. In the other famihes the prothorax is similar to that of 

 Cicada (Figure 3), except that in the Psyllidae (Figures 10 and 

 11), Aphididse, Coccidae and Aleyrodidae it is even more collar 

 like, scarcely overlapping the mesothorax. 



Between the prothorax and the mesothorax of Psyllidae 

 (Figures 10 and 11) there are, according to Crawford, 1914, 

 three small sclerites. One of these, the lower, is the peritreme 

 (pt) surrounding the spiracle. Above this and often separated 

 from it only by a line is a second sclerite (pt) which is probably 

 part of the peritreme. The third of these sclerites (it) occurs 

 behind the above mentioned two, and its origin is not easily 

 traceable. Crawford, 1914,. calls it an accessory sclerite. It 

 would, however, probably come under the term intersegmen- 

 talia used by Crampton, 1914A, 1914B, and would thus be 

 termeei intertergite. Its homologue . was not found in any of 

 the forms treated in this paper. 



Mesothorax. Figures 7, 10, 11 and 12. 



Notum. The mesonotum in the other Homoptera differs 

 only in detail from that of Cicada. The primary divisions — 

 prescutum (psc), scutum (sc), scutellum (si) and postscutellum 

 (psl) — are always present. A w^ell chitinized and fairly large 

 tegula occurs in the mesothorax of Fulgorids (Fulgora sp.), but 

 is not present in other families of Homoptera. 



Pleuron. In the pleuron of the mesothorax several differ- 

 ences are noticeable. The basalares (aba, pba) disappear 

 or become fused to the episternum in some families. The 

 beginning of this is observable in Cicada, where the anterior 

 basalare (aba) is only partly separated from the episternum by 

 a cleft or notch. In the Fulgoridae, Jassidae (Figure 7) and 

 Membracidae no free basalares are to be seen, though one at 

 least is probably present, fused with the episternum. On the 

 other hand, there are usually two basalares (aba, pba) in 

 Psyllids, (Figures 10 and 11), in the Aphids there is at least 

 one (pba), and though they could not be detected by the writer 

 on accovmt of poor material, it is not improbable that one or 

 two occur in the Coccids and Aleyrodids. The pleural suture 

 (p) of the mesothorax is usually distinct among the Homoptera" 

 In some Psyllids, however, it ex^tends but halfway up the pleuron 

 from the coxal attachment. The cleft or notch mentioned as 

 running parallel to the pleural suture in the mesoepisternum 



