This notorious pest was accidentally introduced from Europe to a point near Boston about 1869, and has now spread all over eastern and central Massachusetts, into central and southern New Hampshire, southern Maine, and portions of Rhode Island and Connecticut. It is likely to appear anywhere in the New England and Middle Atlantic states locally at any time, as the result of being carried on freight, trees, automobiles or trains from infested territory to that not yet infested.

The adult moths are found in July and August and a few stragglers may be met with early in September. The female has a large body and grayish-white wings bearing irregular, indefinite, darker markings, and measuring about an inch and a half between the tips of the extended wings. The males are rather smaller, and much darker in color.

The eggs are laid mainly during the latter part of July and August, in clusters of from two hundred to four hundred, mixed with brownish hairs from the body of the moth, which conceal the eggs themselves. The clusters are placed on trees, rocks, fences or on any rubbish at hand, and the eggs remain unhatched until the following spring. The tiny caterpillars escape from the eggs about the time the leaves develop, and begin to feed, and are full grown in most cases during June, being at this time two inches or more in length, rather stout, and with numerous rather long hairs, though the caterpillar could hardly be called" furry." These caterpillars now crawl from the leaves to the trunk, fences or rocks, and here they spin a few scattering silk threads around themselves, and then change to short, brown pupae, within which they change from caterpillars to moths. This change having been completed, the moths escape from the pupae in July or August, and lay their eggs for another generation.

This insect is a very serious pest for several reasons. It feeds in the caterpillar stage on a very large number of trees, shrubs and other plants, and is most voracious. It increases rapidly in numbers and is very resistant to stomach poisons used as sprays. On the other hand, the female moth is so heavy it cannot fly, so that the insect spreads mainly by the caterpillars' crawling, and by the caterpillars' or moths' being carried to new places by vehicles they may get onto.

, The best methods for the destruction of this pest are by destroying the egg clusters during the fall or winter by soaking them with creosote oil mixed with a little turpentine and coal tar. This can be done by using a swab soaked in the mixture and fastened to the end of a pole, pressing the wet swab against the egg clusters. The caterpillars feed mainly at night and hide from the light to a considerable extent in the daytime, hence loose burlap bands around tree trunks will draw many there for concealment, and they can then be easily destroyed. In some cases, spraying heavily with a strong stomach poison, particularly when the caterpillars are young, is quite effective. At present, all hope of a general control of this insect rests in the success of parasitic enemies imported from the native home of this insect, an experiment now being conducted by the United States Department of Agriculture and the State of Massachusetts, in co-operation.