INSECTS INJURIOUS TO AGRICULTURE IN JAPAN 85 



having been characterized by unusually high temperatures and a 

 lack of rainfall, conditions apparently favorable to the development 

 of the insect. There is one brood a year, though according to 

 Aizawa (4) some larvae carry over for two winters. The adult 

 moths appear during July and August, and the winter is passed in 

 the half -grown larval stage in the same manner as by D. spectabilis. 



Dendrolimus superans is found only in Honshu and is a pest of 

 fir and occasionally of pine. There is one brood, but at times two, 

 each year. The winter is passed in the early larval stages. Where 

 there is only one brood the adults appear in late August and Sep- 

 tember, but where there are two the first adults appear in June, and 

 they are then present in greater or smaller numbers throughout the 

 season until October. 



Two Scolytidae, Myelophilws manor, the well-known lesser pine- 

 shoot beetle of Europe, and M. piniperda, the large pine beetle, are 

 found primarily upon pine. According to Yano (207) the first- 

 named is so abundant as often to cause the death of trees in Japan. 

 There are probably three generations per year. The second species 

 is common on the island of Honshu. It tunnels under the bark of 

 the branches, and the newly emerged adults bore into the pith of 

 the young shoots. 



A number of species of sawflies attack pine in various sections, the 

 most common one being Dlprion basalts (5, 207). This species 

 ranges in distribution over Japan, Chosen, Manchuria, and China. 

 In central Japan two broods are produced each year, whereas in 

 Chosen there is only one. This pest causes considerable damage in 

 Japan from April to August. The eggs are laid in rows in incisions 

 in the leaves. The larvae are gregarious in habit and strip the 

 foliage from one branch before moving to the next. In Chosen 

 particularly the young trees are seriously damaged. The larvae 

 are black and, when assembled in large numbers upon a single twig 

 or branch, are very conspicuous. The winter is passed in the ma- 

 ture larval condition in a cocoon in the soil. 



The most common of the scale insects found on pine trees is 

 Poliaspis pini, but none of those mentioned as occurring upon pine 

 are sufficiently abundant to cause noticeable injury. 



INSECTS ATTACKING OAK 



Among the insects attacking oak those of most importance are 

 Porthetrla (Lymantria) dispar, P. mathwra, Drymonia manleyi, 

 and the scale insects Kermes nakagawae and K. miyasakiL 



The gipsy moth, Porthetrla dispar, is a common pest of oak and 

 various other forest trees, particularly larch and poplar, in Hok- 

 kaido and Chosen, and attacks also apple, pear, cherry, and other 

 related fruit trees. In Japan proper this species is restricted to 

 the island of Hokkaido, but according to the various entomologists 

 in that section the periods of abundance of the gipsy moth occur 

 approximately only every five years, and it is only during these 

 periods that injury is produced. According to Okamoto (lJfl) the 

 eggs hatch early in May, and the adults are present from the middle 

 of July to the end of August. In that section the larval stages 

 cover a period of from 7 to 8 weeks, and the pupal stage about 18 

 days. The egg masses contain only from 150 to 350 eggs, a much 



