226 



with equal rapacity upon this insect. From this particular species we 

 have reared no parasites, but in general the Aleyrodidtie are quite sub- 

 feet to the attacks of Hymenopterous parasites peculiar to them. TTe 

 have reared several species of these parasites from other species of this 

 family in this country, but we will leave their characterization and con- 

 sideration to a future article, in which we hope at the same time to de- 

 scribe several species of the family Aleyrodidse found commonly upon 

 different trees in the United States. 



THE PEAR-TREE PSYLLA. 



As an elaboration of the short paper published in Xo. 2 of the cur- 

 rent volume of Insect Life, and first read before the Association of 



Economic Entomologists at Eochester^ 

 Mr. Slingerland gives the results of his 

 observations upon this important pear 

 tree pest in one of the most creditable 

 and useful of the station bulletins.* 



Fsylla pyricola is an old offender and 

 its natural history has been repeatedly 

 treated both in Europe and America, bisfc 

 never before so thoroughly as has been 

 done by Mr. Slingerland. It appears fr-om 

 his careful observations, made in 1892, 

 that the hibernating imagos emerge from 

 their winter retreats on the first warm 

 days of spring, copulate, and commence 

 to lay eggs about the middle of April. The eggs hatched about fom^ 

 weeks later, and the imagos of this first summer generation appeared 

 fr-om June 10 to June 15. The cycle of the second generation was 

 comiDleted about one month afterwards, that of a third generation also 

 one month after the second (about August 20), and the 

 imagos of a fourth generation, which issued toward 

 the end of September, lived throughout the winter. 

 The development of the second generation was 

 carefully followed out with the following result : 



Fig. 2o.—Psylla pyricola: fuH-gro-vni 

 nympli. dorsal view— enlarged (after 

 SliBgerland) . 



First larval stage : duration six or seven days. Larva 0.013 

 inch in length, antennae 3-jointed; Tving-pads not visible; 

 general color pale translucent yellow, without markings ; ab- 

 domen more opaque and darker. 



Second larval stage : duration about four days. Larva one- 

 third larger than first stage, but of same color, except that the 

 tips of antennse are black. Antennse 4-joftited; segments of 

 abdomen more distinct, and -wing-pads developing. 



Third larval stage : duration about three days. Larva 0.027 inch in length; black 



* Bulletin 44, Cornell L'niversity AgTicultural Experiment Station, Entomological 

 Division. Ithaca, N. Y., October, 1892. 



Fig. 2Q.—Pi>yUa pyri- 

 cola: adult — enlarged 

 (after Slingerland). 



