180 



be several times that of the insect, rapidly increasing until it forms a 

 good-sized drop. This, wlien there are millions to aid in the work, 

 soon becomes abundant enough to fall as a shower from the tree when- 

 ever it is shaken by the wind orother means. Mr. Slingerland shows that 

 there are 5 molts, including the last change from the pupa to the adult 

 insect, and the life from the laying of the egg to the adult covers a 

 ])eriod of about thirty days, the periods between molts varying from 

 three to seven days. In Maryland, the second brood, as indicated, 

 had already entirely transformed to the adult stage by the 21st of 

 July, and allowing a month for a generation to include the egg period, 

 we ought to expect a third brood of adults about the iirst of Septem- 

 ber, which will probably be the hibernating brood.' 



NATURAL ENEMIES. 



No enemy for this insect among the parasitic and predaceous species 

 has hitherto beeu recorded. On my first visit to the orchard of Mr. 

 Emory I was shown what was taken to be the egg of the Psylla, which 

 proved, however, to be the egg of a common lace winged fly, Chrysopa 

 oculata Say. The mistake was a very natural one, because the eggs 

 occurred in such extraordinary numbers throughout the orchard. On 

 some trees nearly every leaf would have one or two eggs of the Chry- 

 sopa attached to it. I immediately inferred that the abundance of the 

 Chrysopa was an incident of the extraordinary multiplication of the 

 Psyllas, and recognized that the latter had a very important enemy 

 in the larva of the lace winged fly. At this visit I did not have time 

 to investigate the nuitter further, but on the second visit nearly full- 

 grown larvje of the Chrysoi)a were found on the pear trees attacking 

 and devouring the adult Psylla in a very vigorous manner. I collected 

 a large quantity of the (Chrysopa eggs and bred a number of young 

 larvje, and found that they would feed with great readiness on both the 

 eggs and the young larval Psyllas.^ I think it a safe estimate to say 

 that one lace- wing fly larva will easily destroy several hundred eggs 

 and larvje of the Psylla in addition to the adults which it will destroy 

 in its later larval growth. From the great numbers of the Chrysopa 

 eggs on the pear trees it is not at all improbable that the lace- winged 

 fly alone will bring the Psylla j^retty well into subjection. 



Two or three species of ladybirds were also observed running about 

 over the i)ear trees, the commonest one being Adalia hipunctata L., a 

 little red species with two black spots on its elytra. One of these latter 

 species was seen in the orchard with an adult Psylla in its mandibles, 

 and in my breeding cage at Washington one or two adults cleaned the 



Numerous belated species of the July brood were caged on potted pear trees Aug. 

 3 and produced a new brood of adults by Aug. 30 and these still another by Oct. 1. 

 None of these, even of the last brood, showed any variation from the summer form. 



On some trees that were infested with a rhutoptus sp., allied to the pear-leaf 

 blister-mite, but living exposed on the lower surface of the leaves, the Chrysopa 

 larva- were observed also to devour the mites of this species with great avidity. 



