132 IOWA ACADEMY OF SCIENCES. 



trunks of trees. Toward the top of the tree the bark is younger, less rough- 

 ened, and therefore furnishes less protection for the insect. Consequently, 

 very few of the adults are found in the top of the tree and out toward the 

 end of the branches. 



During the latter part of March, as the days grew warmer, the adults 

 became active, but moved about very little. During the afternoon ot April 

 7th, which was warm and pleasant, they were out toward the ends of the 

 limbs; but as night came on most of them went back to the trunk of the 

 tree, only a few remaining on the slight excrescences of the bark, in the 

 angle between two twigs, or at the base of a large bud. They could be 

 removed from the last named places by simply shaking the limbs. Hence, 

 if they settled down for the winter on the twigs, the many fierce winds 

 would soon sweep them off and carry them to destruction. 



About April 30th the buds of the trees began to swell and open out for 

 the year's growth. The Psyllidse now begin to migrate to the buds and 

 probably feed on the juices of the young tissue. 



The first eggs were found on the young leaves May 5th. After this time 

 the adult females could be found depositing eggs in the opening buds and 

 on the undei'side of the expanded leaves. In the opening buds, where the 

 leaf veins are small and close together, they tend to deposit the eggs in rows 

 between the veins; but as the leaves expand to their full size, they are 

 deposited at random and in large numbei's. 



Adult females of different species are often found depositing eggs on the 

 same leaf. Hence the larvre, and later on the galls of all the species are 

 found on one leaf. The time of first egg deposition depends largely on the 

 season and the location of the tree. If, for example, a tree is located in a 

 warm, sheltered place, the adults become active, the young leaves put forth 

 and consequently the eggs will be deposited earlier. If the tree is in a cold, 

 exposed place, the development of both tree and insect is retarded. More 

 time is required for the eggs to develop on exposed trees than on those more 

 favorably located. This indicates that a low temperature retards the devel- 

 opment of the embryo. In general the eggs seem to develop best at the 

 temperature most favoi'able to the healthy growth of the leaves. During 

 the month of May eggs are continually deposited. May 27 a number of eggs 

 on one tree were compared, and judging by their general appearance, some 

 were recently deposited, while others were quite well developed. On a tree 

 vei-y favorably located a number of the young larvce were found on the 

 upper surface of the leaf. After searching sometime for larvte, a leaf was 

 found bearing a small gall already closed around the insect. On the upper 

 side of the leaf this gall was but slightly raised, having a small cone-shaped 

 projection. On the under side the gall was roundish and covered with a 

 white frosty pubescence. Careful dissection of the gall revealed a young 

 larva which proved to be identical with those on the surface of the leaf. 



From the above stated facts we learn that there is a great variation in the 

 hatching of the larvre. This variation continues throughout the larval stage 

 and greatly augments the difficulty of working out the successive stages 

 in their development. 



From May 27 to June 22 the larvas appeared in great numbers and many 

 galls were starting. From this time till August 16 larvas developed quite 

 slowly. The galls, however, developed quite rapidly and in a short time 



