4 BULLETIN 85, UNITED STATES NATIONAL MUSEUM. 



The present study has been based on a large number of species, 

 representing many genera of the family, as follows: Livia vemalis 

 and L. coloradensis, Ayhalara veaziei, PauropsyUa sp. (a Javanese 

 species), Paurocepliala magnifrons, ApsyUa cisteUata (Indian), Pha- 

 copteron lentiginosum (Indian), HeteropsyUa texana, EupliyUura 

 arhuti, Arytaina robusta, Psyllopsis fraxinicola, Psylla alni americana, 

 Psylla pyricola, Trioza diospyri and T. albifrons, Paratrioza arholensis, 

 and many others compared but studied less carefully. 



Apsylla cisteUata, an Indian species, is somewhat generalized and 

 proved to be very valuable for indicating the path of specialization 

 in the more highly specialized forms, or those considered to be more 

 typical of the family. It was pointed out in the description of this 

 species (Crawford '12c:421, 429) that it was scarcely psylline in many 

 respects, and in fact the generic name, Apsylla, was suggested by 

 that fact. Many developments so complicated and so highly special- 

 ized in Psylla that it is extremely difficult to understand them 

 become much clearer when the Indian species is compared with them. 



The methods of study used have been both gross dissections and 

 microtome serial sections in balsam. The dissections were made 

 in a liquid — alcohol, cedar oil, or glycerine being the best, and for 

 most purposes alcohol the best — and under a binocular microscope 

 with a magnification of about sixty diameters. The specimens were 

 first softened, cleared and distended in a warm, strong solution of 

 caustic potash and then placed in a watch glass on the microscope 

 stage with a strong tungsten light directly beneath the stage. In 

 this way the sclerites of the exo-skeleton become easily visible because 

 of the semi transparent and distended condition of the body wall. 

 By means of fine needles and special tweezer-like scissors the insect 

 may be very easily dissected. 



Another method of dissection which proved to be very valuable 

 and which is offered as a suggestion to others for similar work is as 

 follows : Soak the specimens in warm caustic potash for ten or twelve 

 hours, then place in water for a few minutes, and dehydrate with 

 alcohol; then soak in cedar oil for several hours and imbed in par- 

 affine. With a microtome, section away one-half of the insect, either 

 longitudinally or sagitally, dissolve away the paraffine from the 

 remaining unsectioned half with xylol, and mount in balsam with 

 the cut surface up. No staining is necessary unless a chitin stain 

 is used in cases where the body wall is mostly depigmented and 

 transparent. A half insect mounted with the open side up shows 

 with remarkable clarity and perspective the internal skeleton and 

 the internal side of the sutures. This method was found to be 

 valuable also for the study of the musculature, but of course for 

 this the specimen must be first fixed aUve instead of soaking it in 

 caustic potash. 



