. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 16 BULLETIN 1429, 17. 5. DEPARTMENT 0] AGRICULTURE climate is considerable colder than at the latter place, the season I»f i i» lt confined to June, July, and August. Becau • as and meadow lands here Popillia is more abundant than bo wnnl, although it is n«»t an eoonomic pest. The first beetles of the son appear about July l. increasing rapidlj to maximum numl by July 24, after which the decline is gradual through August, and by September 10 only a few arc left. Here approximately 21 per cent of the beetles undergo a t
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 16 BULLETIN 1429, 17. 5. DEPARTMENT 0] AGRICULTURE climate is considerable colder than at the latter place, the season I»f i i» lt confined to June, July, and August. Becau • as and meadow lands here Popillia is more abundant than bo wnnl, although it is n«»t an eoonomic pest. The first beetles of the son appear about July l. increasing rapidlj to maximum numl by July 24, after which the decline is gradual through August, and by September 10 only a few arc left. Here approximately 21 per cent of the beetles undergo a two-year cycle. This cn<i seems constant in northern Honshu. At Sapporo hit. 43 X. on the island of Hokkaido, and aboul miles north of Yokohama, Popillia is more abundanl than elsewhere in Japan, perhaps because of the presence of extensive grass and meadow lands which afford undisturbed breeding grounds. It is said that at times the adults occur in such numbers as to cause dai to the foliage of the soybean, although in four year-' observations the writers no material damage to any economic crop was Fig. 31.—Diagrammatic calendar of the fluctuating biennial broods of Popillia japonka at Sapporo, Japan. Lines 1, 2, 3, and 4 represent, respectively, 25 per cent of the stages passed in the soil, eggs, larvae, and pupae. Solid black curves represent adults as they occur during the seasons. Winter months are omitted for convenience. The years 1920 and 1922 were seasons in which only 25 per cent of the larvae (Xo. 1) transformed to adults, larvae Nos. 2. 3. and 4. or 75 per cent, remaining in the soil to transform the following seasons. The years 1921 and 1923 were seasons in which practically all larvae transformed into adults. Curves for adults in 1920 and 1923 havr their apices about July 20, or 10 days earlier than normal, because of the intensive parasitism by Centeter cinerea. Curves for adults in 1921 and 1923 represent normal abundance with apices at the end
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