INSECTS INJURIOUS TO AGRICULTURE IN JAPAN 



69 



lection of egg masses, putting out molasses traps for adults, digging 

 ditch traps along the field borders, and fall plowing and spraying 

 with lead arsenate while the larvae are in the early stages. 



A very important pest of soybean found extensively in Hokkaido 

 and Honshu is the olethreutid moth Laspeyresia glydnivorella 

 (149)i which is also recorded by Sanga (158) as abundant and 

 injurious in Manchuria, where that crop is the most important of 

 all agricultural products. There is but one brood a year, and the 

 winter is passed as a mature larva or prepupa in a light cocoon 

 in the soil. Pupation takes place about the first of June, and the 

 adults emerge toward the end of July. The eggs are laid singly 

 or in small groups upon the developing pod and hatch in from 

 six to eight days. The young larvae burrow into the pod and feed 

 upon the developing seeds. When mature, at about the end of 

 October, they enter the soil and spin the cocoon. Cultural experi- 

 ments reported by Takahashi (192) have shown that the early 

 maturing varieties of soybean had much lighter attacks than the 

 later varieties. With the early-maturing varieties early planting 

 gave a better yield as well as a lower percentage of infestation, 

 whereas with the late-maturing varieties early planting gave a 

 higher yield also, but the advantage was offset by the heavier 

 infestation of Laspeyresia. The comparative figures of the injury 

 are as follows : 



Percentage of 

 Early-maturing varieties : grain injured 



Early planting 23.7 



Common planting 33. 3 



Late planting 66.6 



Percentage of 

 Late-maturing varieties: grain injured 



Early planting 64. 7 



Common planting 58. 



Late planting 44. 3 



For control Ishii and Okamoto (41) recommend fall plowing to 

 bring the cocoons to the surface where the insects will be killed 

 by the winter's cold. 



Another olethreutid common on red bean in Hokkaido and Honshu 

 is Thiodia azukivora (95). One or possibly two broods are pro- 

 duced each year, and the larvae feed much after the manner of 

 L. glydnivorella. The winter is passed in the pupal stage in the 

 soil. Hand collection of adults is the only control measure suggested. 



The pierid butterfly Colias hyale polio graphics (76) is a general 

 pest of legumes in Japan. Three or four generations are produced 

 each year, and hibernation is in the adult stage. 



The lycaenid Larmpides oaeticus (95) is a common pest of beans 

 in Kyushu and the island of Okinawa. There are two broods each 

 year, and the winter is passed in the egg stage. The larvae feed 

 upon the seed in the pod, and pupation occurs upon the leaves 

 or stem. 



The chrysomelid Lup erodes discrepans (149) is a very serious pest 

 of soybean, as well as of sugar beet and clover, throughout Japan. 

 There are two broods a year, the winter possibly being passed in 

 the egg stage. The life history is imperfectly known, but larvae 

 appear in the field in the middle of May, later pupating in cells 

 in the soil and emerging as adults in July. Feeding continues until 

 the end of September, and much damage is done. The spring brood 

 of larvae feed upon the newly developed main leaves of the young 

 plant. L. discrepans differs from nigripennis, with which it is often 



