INSECTS INJURIOUS TO AGRICULTURE IN JAPAN 89 



each year, the adults appearing at the end of May. The eggs are 

 laid singly upon the trunk and hatch in two weeks. The larvae are 

 mature at the end of August, when the cocoons are formed, and 

 pupate one month later. The winter is passed as pupae. The 

 cocoon may be formed either in a crevice in the trunk, in which case 

 fragments of wood are used in its composition, or in the soil. 



The noctuid Acronycta leporine leporella (1^9) occurs through- 

 out Hokkaido, Honshu, and Siberia, and feeds upon birch as well 

 as poplar. There is one brood a year, the adult moths appearing 

 early in June and laying their eggs singly or in small groups on the 

 undersides of the leaves. These eggs hatch in about seven days, 

 and the larvae are mature by the end of July. Pupation occurs early 

 in August, and the winter is passed in the pupal stage. 



Melalopha anastomosis {1J$) occurs as a pest of poplar and willow 

 throughout Japan, Chosen, China, and Siberia and ranges westward 

 to Europe. In Hokkaido two or three broods occur each year. 

 Where there are two broods the adults are found in late May to 

 June and early in August. Where there are three broods the first 

 two coincide in time with the above, and the third appears the latter 

 part of September. The eggs are laid in masses of from 300 to 400, 

 from 4 to 6 layers deep, on the undersides of the leaves. These 

 hatch in 1 week, and the larvae are mature in 5 or 6 weeks. Pupation 

 is in a thin cocoon within a folded leaf. The adults of the early 

 broods emerge in one week, but the pupae of the last brood go into 

 hibernation. 



The gipsy moth, Porthetria dispar, is found very generally upon 

 poplar in northern Japan, and this tree is the preferred host of the 

 variety japonica in Honshu and Kyushu. 



The chrysomelid beetle Plagiodera versicolora var. distinct a (8) 

 is common upon willow in Chosen. There are two generations each 

 year, and the winter is passed in the adult stage in rubbish and in 

 other sheltered places. The adults appear in the field in early May 

 and the females deposit their eggs about two weeks later. The larvae 

 feed upon the lower epidermis of the leaf, and are mature in about 

 17 days. The pupal stage, also passed upon the foliage, covers only 

 4 days. The adults emerge the latter part of June, but those of the 

 following generation, which live over the winter, reach maturity 

 about the first of September. 



Popillia japonica, the Japanese beetle of the United States, feeds 

 extensively upon poplar, this being, next to Polygonum, the favored 

 food plant. In Hokkaido the beetles were observed each year in 

 large numbers feeding upon the foliage of the uppermost branches, 

 and these were often stripped of leaves when the beetles from a con- 

 siderable area had congregated upon a relatively small number of 

 trees, but the foliage of the lower and middle part of the trees was 

 seldom damaged. 



The sawfly Tricliiocampus populi (14$) is abundant in Hokkaido 

 and Sakhalin. The adults appear the middle of June, and eggs are 

 laid in an incision made in the leafstalk. These hatch in about two 

 weeks, and the larvae feed upon the lower surfaces of the leaves. 

 They are gregarious in habit, feed chiefly at night, and move from 

 tree to tree, often producing complete defoliation. The winter is 

 passed in the mature larval stage in a rough cocoon in rotten wood 

 or in the soil, the pupa being formed at the end of May. 



