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Howard (1895) states that E. V. Wilcox sent him specimens of the beetle and the larva from Cambridge, Massachusetts, reporting that willows in that section were severely infested. Jack (1897) records the beetle as being very abundant about Boston and Cambridge, it having been present in the Arnold Arboretum for many years and at that time proving very injurious to many species of willows and poplars and to two species of birches. Up to that time it had been supposed that the insect was restricted to the eastern Atlantic border, but in 1896 Ottomar Reincke collected it near Buffalo.

The beetle has now become well established in the Eastern States but its westward and northward spread has not been very rapid. Burgess (1903) records it from Ashtabula, Ohio, in 1901; Bues (Bues and Sandsten, 1904), from two nurseries in Wisconsin in 1903; and Washburn (1904) reports receiving specimens from the extreme northwestern corner of North Dakota, where the insect had been introduced on nursery stock from New York. This stock had been first shipped to a Minnesota nurseryman, who in turn had distributed it, some of it reaching northwestern North Dakota. It is clear that the beetle was thus, in all probability, widely distributed in the Northwest.

Patch (1908) first observed the insect at Orono, Maine, in 1907, and in 1911 it was found also at Augusta and at Presque Isle. Forbes (1911a) records the beetle from Chicago in 1908, where it was abundant and destructive throughout the city. He reports that it has not been found elsewhere in the State.

FOOD PLANTS

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The poplar and willow borer has a fairly wide range of food plants. European writers record it as attacking the following species: alders Alnus viridis DC., A. incana Willd., A. glutinosa Willd.; willows - Salix caprea L., S. viminalis L., S. purpurea L., S. triandra L.; poplars Populus alba L.; birches - Betula species. Jack (1897) states that in America all the native willows except the slender-stemmed species are subject to attack. This is confirmed by C. S. Sargent, Director of the Arnold Arboretum at Cambridge, Massachusetts. Of the imported willows the following have been observed injured in the Arnold Arboretum: Salix alba L., S. fragilis L., S. babylonica Tourn., S. pentandra Linn.

The following species of poplars are also recorded as host plants: Populus balsamifera L., P. deltoides Marsh., P. alba L. Schoene (1907 a) records the following species of willows as host plants: Salix lucida Muhl., S. caprea L., S. cordata Muhl., S. sericea Marsh., S. alba L., S. amygdaloides Anders. In addition two species of birch are known to have been injured-Betula pumila L. and B. nigra L. These, however, are rarely

attacked.

[graphic]

FIG. III.

TRUNKS OF SEVERELY INJURED CAROLINA POPLAR TREES, FIVE YEARS OLD

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At right and left, five-year-old trees, severely injured an uninjured four-year-old tree in the center. All were grown under identical conditions in the experimental plot

ECONOMIC IMPORTANCE

The poplar and willow borer is of greater economic importance than has generally been supposed. It is a serious pest of practically all species of willows, and where the beetle is abundant the damage done is extensive. This is especially true of all varieties of ornamental willows. Also the production of basket willows is greatly reduced and in many cases stopped by the work of this insect. To many species of poplars it is very injurious, especially when the trees are young (figs. 111 and 112). In many nurseries the production of poplar stock has been discontinued owing to the prevalence and injuriousness of the pest.

The willows (Salix species) and the poplars (Populus species) are regarded generally as of not much value. However, many willows are used extensively in landscape work, not only for their quality of rapid growth but also for their beauty. Species native to this country line the streams and encroach on the boundaries of lakes and ponds, serving a very useful purpose as holders of the soil. The carolina poplar, though not looked upon with much favor as a shade tree, has been and is being planted rather extensively in recently developed areas. This is especially true in the Middle West, where the trees soon become suitable for lumber. Extensive plantings made from forty to fifty years ago in the Middle West, and also the great areas of cottonwood in the lower Mississippi Valley, are now being lumbered. The product finds a ready sale as lumber and commands a good price for excelsior. The carolina poplar is used also on sandy areas to keep the soil from being washed away.

The balm-of-Gilead poplar, which is used generally as a shade tree, is severely attacked by the borer. The branches serve excellently for the development of the insect, and in sections where it is prevalent scarcely a sound tree can be found. The branches, weakened by the larval burrows, are broken off by high winds and ice storms, rendering the trees unsightly.

In Europe the beetle has proved a pest to many species of willows, poplars, and alders. Many accounts are given of its destructive work, and there is no doubt that it is proving even a worse pest in America.

DISTRIBUTION

The beetle, recorded as having first appeared in America in 1882 (Juelich, 1887), has not spread very rapidly. It is at present known to occur from Maine west to Ontario and North Dakota and south to the District of Columbia. Throughout this area it is restricted to certain localities, and once introduced it does not spread rapidly unless carried by some agency. It is reported by Fletcher and Gibson (1909) as occurring at Dundurn

Saskatchewan, but nothing is known as to its spread in this province. It has not been found west of the Great Plains.

The preceding statement as to the general distribution of the beetle is based on letters received from various officials regarding the situation. in their respective States. P. A. Glenn informs the writer that in Illinois the beet'e is abundant about Chicago and occurs generally in the northern. fourth of the State, while in the central and southern parts it has not been found. Dr. Fracker reports it as widespread in the nurseries of Wisconsin, where it has been found as far north as the shores of Lake Superior. Blatchley and Leng (1916) state that it has not yet been found in Indiana. Professor R. H. Pettit says that it is common in Michigan and probably occurs wherever the carolina poplar grows. In Ohio it seems not to have spread to any considerable extent since its first appearance there in 1901. It has not yet been found in Nebraska, South Dakota, Iowa, or Indiana.

In Canada, according to Caesar (1916), it is well distributed throughout Ontario and is also recorded from a few localities in the province of Quebec.

LIFE HISTORY

Although this beetle has been a serious pest in Europe for hundreds of years, its life history has never been fully investigated by European workers. Even at present there is the widest divergence between the accounts given by American and by European writers. This is brought out in detail in the discussion of the various activities of the different stages.

The adult

The poplar and willow borer (Plate xxII) belongs to the great group of snout beetles, Rhynchophora, and to the family Curculionidæ. This family contains an immense number of species, many of them very serious pests, including the common plum and quince curculios. The beetle measures from to inch in length, is robust, and is elongate-oval in shape. It is densely clothed with black and pale-colored scales, intermixed with erect, large, black bristles. The pale scales cover the apical third of the elytra and form an irregular band on the basal third; the underside of the prothorax and part of the legs are also densely clothed with them, and the remainder of the body bears a few scattering ones. The beak is curved, is as long as the head and the thorax, and lies when at rest almost completely concealed in a groove on the ventral surface of the thorax. The antennæ are elbowed and reddish brown, with an unsegmented club.

The beetles begin to appear during the latter half of July, becoming abundant in August. The writer found them present on poplar trees

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