1903] MORRILL:— TING I TIDS OF THE GEXUS CORYTHUCA 131 



side of each wing pad about four fiftlis of the distance from the tip to the base is a prominent 

 shoulder. The rostrum reaches to about the middle of the mesothorax. The fourth segment 

 of the antenna is now about one half as long as the third. Spines of types nos. 2 and 3 are 

 more numerous than before on the antennae and legs. On the head four more spines of tvpe 

 no. I appear in connection with the group present in the previous in star : — one on each side 

 of the second (next to the anterior) group, and one on each of the two posterior groups. A 

 few small spines of type no. i appear for the first time on the sides of the pro- and meso- 

 thorax and of the fourth to ninth abdominal segments. The second and third abdominal 

 segments have lost the spines of type no. i which in previous instars were present on their 

 lateral margins. The area covered by the minute dark spines is much more limited than 

 before. The integument is shaded with brown as before except where there are large spaces 

 devoid of these small spines ; the color here is dull yellow, thus giving a somewhat broken 

 light band across the body in the region of the tips of the wing pads. The facets of the eyes 

 are much more numerous than in the previous instar. 



The eggs of the Oak Tingis are found on the under surfaces of the leaves, 

 usually near the larger ribs and in groups ranging from two or three to more than 

 one hundred in numbers. Single isolated eggs are occasionally found. Judging 

 from the number of eggs as compared with the number of adults early in the sum- 

 mer, many eggs must be laid by each female. During the last few days in May of 

 the present year (1903) it was observed that, on those oak leaves where any of the 

 insects occurred, a male and a female were usually found together; rarely one and 

 still more rarely three and four individuals, were found on a single leaf. On many 

 of the leaves where there was but one pair of the insects the numbers of eggs ranged 

 from twenty-five to fifty. 



The nymphs remain together in clusters. Their wanderings on the under sur- 

 face of a leaf are marked by their shiny, black, rounded excrements which are 

 apparently deposited on the leaf by means of the peculiar tenth abdominal seg- 

 ment already described. The moulted skins of the nymphs remain attached to the 

 leaf by their tarsal claws as already observed by Comstock in the Hawthorn 

 Tingis. 



The upper surfaces, particularly along the sides of the mid ribs, of leaves of 

 badly infested trees, turn dirty pale green, sometimes mottled with reddish, and the 

 ornamental effect of whole trees may be greatly impaired by midsummer unless 

 spraying is resorted to. 



From two to three days intervene between each succeeding moult up to the 

 fourth, and from six to seven days between the fourth and fifth moults. The 

 duration of the egg stage is unknown to the writer, but eggs laid on the leaves of 

 certain oaks on the college grounds about the middle of May were unhatched on 

 June first, the time of the present writing. 



The adults hibernate beneath the bark, under leaves, and among rubbish. 



