260 The Ohio Journal of Science [Vol. XVI, No. 7, 



Five psyllid galls belonging to the genus Pachypsylla are 

 herewith presented. The author concurs with Crawford (4, 

 p. Ill) in his monograph of the Psyllidae, when he asserts that 

 the following species of Pachypsylla erected by Riley (28) in 

 the Fifth Rep't of the U. S. Ent. Comm., viz.: P. astericus, 

 umbilicus, pubescens, globulus and curcurbita and P. rohweri 

 Ckll, are "only variations of the species of P. mama, since the 

 insects are said to be similar and the differences in the galls are 

 not great." These species evidently represent intermediate 

 forms between P. mama Riley and P. vesiculum Riley, though 

 they are much closer to the former than the latter. The 

 writer has noted the wide variation obtaining among the P. 

 mama forms. The above named species will not be included in 

 this paper, since their validity is rightly doubted. There are 

 three species known other than those whose galls are dealt 

 with in this paper, viz. : P. dubia, pallida and inteneris, but no 

 galls are described with them. They are all said to be closely 

 related to P. gemma Riley and may ultimately prove to be 

 varieties of that species. 



In the following studies diagrammatic presentation is 

 resorted to in the elucidation of entire gall sections. Lignified 

 tissue entering into the formation of the protective layers 

 is shown by cross-hatching; simple stippling indicates paren- 

 chyma and the vascular bundles are outlined. The portions 

 of the sections furnishing the diagrams used in detailed studies 

 are outlined on the diagram. 



3. Pachypsylla vesiculum Riley. This, the simplest of the 

 psyllid galls, is a small (2-3 mm. dia.) monothalamous "blister" 

 gall of the intervenal tissue, commonly found close to the 

 principal veins of the leaf. They are apt to occur in great 

 numbers. More or less evenly convex above; a small, rounded 

 central papilla can be determined below. The galls, both 

 above and below, become lighter in color than the normal leaf, 

 though very green when young. Easily evident from the 

 latter part of May on through the summer. 



Riley, Sth Report U. S. Ent. Comm. p. 618. 1890. 



The section of the gall in its position near a principal vein, is 

 shown in PI. XIII, Fig. 3. The convex zones of sclerenchy- 

 matized cells are very definite, extending over either side of the 

 chamber, forming the protective envelope; protective in the 



