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[[strikethrough]] 20 [[/strikethrough]] [[strikethrough]] 13[[/strikethrough]] 50 CHARLES V. RILEY and L.O. HOWARD. The three Pear tree Payllas. Insect Life, IV, Nos. 3 and 4, November, 1891, pp. 127-128. Abstract of a paper by Dr. F. Loew pointing out the differences in life habits of the three species of Psylla (Ps. pyrisuga, Ps. pyri, and Ps. pyricola known to infest pear trees in Germany and Austria, with a synoptic table of the structural characters. Also characteristics of a fourth species, Ps. simulans which has been found in England on pear trees.