POPLAR BORERS. 439 



7. The poplar goat-moth. 



Cossus centerensis Liutuer.* 



Plate I, tigs. 1-12. 



Order Lepidopteka ; family COSSID^. 



Perforating the trunks of Popiilus tremuloides, a worm similar to, but smaller than, 

 the oak caterpillar (X robinia;), the moth issuing from the trees during June. (Bailey.) 



lu connection with the following account bj^ Dr. Bailey we may say 

 that Mr. Fletcher reports that he has found about Ottawa this moth 

 common on the balm of Grilead {Populus balsamifera). The pnpa is 

 usually extruded from the bark about 4 o'clock in the afternoon, when 

 he has frequently seen them. (Can. Ent., xv, p. 203.) 



Cossus centerensis (Plate I) was discovered by Dr. Theodore P. Bailey in 1877. For 

 many years previous I had observed that many trees of Populus tremuloides had per- 

 ished from some cause then unknown. The central shoots of other trees of the 

 same species were dead, and it would only require a few years to finish their destruc- 

 tion. Perforations were found in the trunks of these trees, some of recent date and 

 some overgrown with bark, leaving the cicatrices plainly visible. 



In July, 1876, a brittle pupa-case of the Cossus was found projecting from one of 

 the openings, which gave the first clue to the nature of the borer and destroyer of 

 the timber. 



On the 10th of June, 1877, a fresh pupa-case was discovered, and on the 14th of the 

 same month the first Cossus was captured, resting upon the sauie tree trunk. Every 

 season since this capture the Cossus has been taken, but in some years in greater 

 numbers than others. 



The Cossus usually comes forth between the setting and rising of the sun, and when 

 the trees are visited daily the protruding pupa-cases left behind by the escaped im- 

 agines informs the collector how many of the insects he may expect to find. 



Their color simulates so closely the color of the bark of the trees that it requires 

 good ejes and very close observation to find the moths. One unaccustomed to collect 

 them might view an infested tree for a long time and not find a Cossus, when several 

 would be discovered by an expert. An uneven protuberance on the bark, or the 

 short stump left of a decayed broken limb are favorite resting places for the insect. 



The moth at first is rather sluggish, and can be easily captured. After it has been 

 abroad for some days it is wild and more or less mutilated. This Cossus is not 

 attracted by sugar, as might be expected from its aborted tongue. The moth seems 

 to belong to the genus Cossus Fabr., and not to be congeneric with Xystus robiniw. The 

 head is short, eyes naked, labial palpi small, appressed, scaled. The thorax is thickly 

 scaled, the scales gathered into a ridge behind, and is squarer in front than in Xystus, 

 not so elongate or so elevated dorsally. The male antenngs are bipectinate ; the 

 lamellae rather short and ciliate. The female antennae are serrated. It is allied to 

 the European Cossus terebra F., but is a larger insect. It difters from C. querciperda 

 Fitch by the absence of any yellow on the male hind wing, and by its darker color 

 and closer reticulations. 



In color this species is black and gray. The edges of the thorax and collar are 

 shaded with gray, more noticeable on souie specimens than others. The primaries 

 are covered with black reticulations, which are not always identical in their minor 

 details in different specimens, nor sometimes on both wings in the same specimen. 



* The following account of this fine moth was published by the late Dr. James S. 

 Bailey, of Albany, N. Y., in Bulletin No. 3 of the Entomological Division of the U. 

 S. Department of Agriculture. 



