stough: the hackberry psylla. 161 



covering the tips of the blades dorsally and laterally, and open 

 entad and ventrad. The basal portion is evidently a complex 

 made up of parts corresponding perhaps to the median rod, 

 lateral rods and lateral plates, with their processes, append- 

 ages, etc., of Pachypsylla, while the two scabbards may be 

 homologous to the sheath. The sting-palpi are not repre- 

 sented in Cicada. 



The ovipositor of one species of Aleurodidse which I have 

 examined showed features most similar to those of Pachy- 

 psylla of any other insect, the parts being much more easily 

 compared with those of this insect. The upper and lower pairs 

 of converging blades or styles were found, together with a 

 sheath enclosing their apices, while their bases bore irregu- 

 lar supports as in Pachypsylla. Sting-palpi and sc 1 and sc 2 

 were also present. 



GENERAL SUMMARY. 



1. The head is made up of the typical sclerites. 



2. The mouth parts conform in general to those of other 

 homopterous forms, such as those of the Cicadidse, Aphididse, 

 Aleurodidse, and most closely to those of the Aleurodidse, differ- 

 ing most from those of the Coccidse. 



3. The mesoterga and metaterga show three sclerites only. 

 The pleural sclerites are much folded, with their sutures almost 

 obsolete. The internal skeleton of mesothorax and metathorax 

 is large and heavy, making the segments very rigid. 



4. The metathoracic legs are greatly specialized for jump- 

 ing, the tibise being provided with heavy spines on their distal 

 ends, and the coxa, epimeron, meracanthus, a part of the 

 sternum, and an accessory sclerite compose a single complex 

 of sclerites which encases powerful jumping muscles. 



5. A study of the tracheation of nymphal wing pads and 

 wings of recently emerged adults has shown that there are 

 present in the adult wing the following veins : one costa ; one 

 subcosta ; one radius ; one two-branched media ; one two- 

 branched cubitus ; one anal vein ; and a vein occupying the 

 anal fold, seen only in nymphal wings, being represented only 

 as a fold in the adult wing. Previous writers have not indi- 

 cated the media and cubitus as separate veins, but I have shown 

 them to be represented by separate parallel trachese in the wing 

 pads. The subcosta of the hind wing, previously unfigured, 

 was found in recently emerged specimens. A sport vein, pos- 



