p. R. AwATi 265 



enters the cavity formed by the ovipositors. J^istally there are recurved 

 minute hairs which prevent the egg from going back. One egg is laid 

 at a time. 



(v) The maximum number of eggs produced by a female in one 

 case was 30, in another 37. 



(vi) The egg-laying season. This is very short and only extends 

 over a week. The females began egg-laying early in September. By 

 the middle of the month the season was over. 



(vii) The males and females seem to outlive this egg-laying season 

 for some time. They are found as late as October and they appear to 

 die towards the end of that month. In November I could not find 

 any specimen of the Psylla mali. 



IX. The Pear Sucker {Psylla pyricola). 



This insect is the most important pest of pear trees on the Con- 

 tinent and in America. Unfortunately, it has recently been found in 

 the United Kingdom, and was reported last year by Prof. Theobald, 

 of the Wye Agricultural College. This insect has the same life-history 

 as Psylla mali, but there are many important differences and features 

 which make this insect more formidable than Psylla mali. 



(1) Eggs. 



They are elliptical and narrow. Their colour varies from pale yellow 

 to brownish yellow. They are found in clusters or groups of 30 or more 

 on the upper surfaces of leaves but scarcely on twigs. They can easily 

 be distinguished from those of Psylla mali. 



(2) The Larvae (Plates XVII, XVIII). 



(i) There are five stages, the imago emerging from the fifth (or the 

 nymph). The first four stages correspond closely to those of Psylla 

 mali in the external structure, but the fifth instar or the nymph is very 

 characteristic of this insect. It is not uniform in colour but is spotted 

 on the abdomen. The other structures seem to be similar, 



(ii) Secretion. These larvae exude a waxy secretion which wets 

 the surface of a leaf. There are no white threads as there are in Psylla 

 mali. The larvae of Psylla pyricola are always wallowing in the secre- 

 tion. On this honey-dew grows the injurious fungus which has been 

 identified by Massee (of the Royal Botanical Gardens, Kew) as Clado- 

 sjporium herbarium. Thus it will be seen that the habits of these larvae 

 as to secretion are quite different from those of the larvae of Psylla mali. 



