In the "North-China Daily News" of September 16 there appeared an extremely interesting news item from New York, dated August 14, describing the invasion, of the. United States by the Japanese beef known to science as Popilia japonica. The report gave details of the depredations this little beetle has committed since it was accidentally introduced in 1916 in a shipment of azaleas from Japan to a small town in southern New Jersey. The Japanese beetle is a member of the chafer family (Scarabaeidae), which also includes the well-known cockchafer, the beautiful metallic green rose-chafer and the so-called May-bug or June beetle of the English countryside. It is of a brown and green colour with a metallic sheen, and is a little over a quarter of an inch in length. In spite of its small Size, however, its voracity and fecundity make it a serious pest when it gains a foothold in countries where its natural enemies are not in evidence. Its eggs are deposited in the turf in lawns and meadows where their larvae begin their career of destruction by eating the roots of the grass. In due course these pupate and finally the perfect insects appear, only to carry on their depredations by devouring the leaves and even the fruits and flowers of all manner of plants, When unchecked by natural enemies, as has been the case in the Eastern United States, these beetles may become so numerous as to make a clean sweep of everything green, rivalling the locusts in this direction. It was several years before their depredations were noticed in this region, by which time they had gained such a foothold that, as the New York report says, they have been able to keep more than a jump ahead of the entomologists called in to exterminate them, and have now spread over an area of 9,000 square miles, mainly in New Jersey and Pennsylvania. Recently, however, they have made their appearance in the very heart of New York City, to such purpose that they have been counted at the rate of fifty to each flower in a roof-garden on the ninth floor of a skyscraper, and are being captured at the rate of 20,000 a day in the city's botanical garden without appreciably diminishing their numbers. There is only one way of controlling such an insect plague and that is to discover and introduce into the affected area some natural such as the Tachinid flies or the Chalcid wasps. whose larvae parasitize the offending insects, as described in my "Nature Notes" of August 29. The difficulty with this method of control lies in the fact that each species of insect pest has its own particular species of parasitic enemies. There are plenty of different kinds of Tachinid flies and Chalcid wasps in America, but each has its own special host and will not parasitize any other insect, so that the stranger from Japan is imjune from their attacks. To find a parasite that will attack the Japanese beetle it is necessary to seek for it in Japan, the land of its origin. As a matter of fact, this has been done, some fourteen years ago by a Dr. J. F. Illingworth, of the United States Department of Agriculture, having come to the Orient on this quest visiting both Japan and China in his search for a suitable parasite of Popilia japonica, I believe he actually secured parasites of both the Japanese beetle, and a very close relation we have here in Shanghai, but it would appear, from the fact that this pest is still gaining ground in the United States, that the parasites he secured have not been as effective as could be desired. Obviously what America wants is a bigger or at least a better Popilia
Text read from the printed page and cleaned; old type leaves the occasional error.