228 



Fig. iS.—l^nylla pyricola : a, head of adult, front view; 

 c, cones of clypeus; o, ocelli; 6, antenna of adult — all 

 enlarged (after Slingerlaiid). 



Psylla simulans is iu Europe a summer form. Dr. Frauz Low* dis- 

 tinctly states: "The imagines were fouudiu summer on these plants" 



[Pyrus mains and P. commu- 

 nis]', and at another placet 

 he states that the si)ecimens 

 were found by himself: " I 

 found this species hitherto 

 only on the apple tree iu com- 

 l)any with Ps. pyricola.''' Mr. 

 John Scott I says of his Ps. 

 pyri {=simulans): "It lives 

 on pear trees, and is to be 

 found from June to October ;" 

 but this is apparently not based on actual observation, and probably 

 taken from Curtis's account of Psylla pijri {—pijrlcola). Finally, it is 

 more than probable that hibernating- specimens of Ps. pyricola have 

 been collected and examined by authorities in Europe. Dr. Fr. Low 

 would scarcely have made the statement regarding the hibernation of 

 this species without having seen specimens found in winter time.§ 



There is plainly an error somewhere and the following explanations 

 suggest themselves : (1) Either Mr. Slingerland may have been dealing 

 with two distinct species occurring at 

 the same time on his trees; or (2) we 

 have been mistaken in the identifica- 

 tion of the winter form as simulans (the 

 determination was made from a study 

 of descriptions and not from compari. 

 son of specimens) ; or (3) the European 

 observations are faulty ; or {-i) the liiber- 

 nating form in central Europe extends 

 into summer. We feel confidence in Mr. 

 Slingerland's views, and shall expect 

 the final explanation to justify them. 



The various life-habits of both the adolescent and adult stages of 

 the insect are more or less fully dealt with by Mr. Slingerland, and of 

 the many interesting and novel observations we select here for quota- 

 tion those made on the houey-dew : 



Many have supposed that the honey-dew, so conspicuous a feature in severe at- 

 tacks of this pest, is the sap of the tree which exudes through the punctures made 

 by the insects. As the honey-dew occurs in such immense quantities it does seem 

 almost impossible that it is wholly the secretion of the little creatures. All of this 

 fluid does, however, iirst pass through the body of the insect. The amount which a 



Fig. 29. — Paylla pyricola: venation of wing.s; 

 «, stigma ; c, clavus; c*, claval suture — en- 

 larged (after Slingerland). 



*Uebersicht d. Psyll. von Oesterreich-Ungarn, etc., 1888, p. 15. 

 tXeue Beitriige, etc., 1886, p. 157. 

 J Trans. Ent. Soc, London, 1876, p. 537. 



vUn his Revision d. paliiarct. Psyll., 1882, p. 232, Dr. Low seems to be inclined to 

 consider Ps. argyroatigma Forst. as the winter form of Ps. simulans. 



