41 



THORN AND WILLOW BORERS : SAPERDA FAYI AND S. CONCOLOR. 



BY JOHN HAMILTON, M.D., ALLEGHENY, PA. 



Saperda Fayi, Bland. — This beautiful Saperda breeds in the small limbs of Crataegus, 

 especially crus-galli and tomentosa, as first observed by Mr. 0. D. Zimmermann, Can. 

 Ent., 10, 220 ; and should it, like some of its allies, acquire a taste for cultivated fruit 

 trees, it would be a formidable enemy, as is evidenced by the way it depredates on thorn 

 bushes. The beetles appear here the last week in May or the first week in June, accord- 

 ing to the season, the males preceding the females three or four days. They do not appear 

 to eat, and are short lived, the whole brood (except stragglers) appearing and disappearing 

 within the space of ten or twelve days, so that should the collector be negligent, or the 

 weather unsuitable for collecting at the time of their appearance, he may get none till the 

 next season. As soon as the females appear the males are ready to associate with them, 

 the union lasting three or four hours. They are not much given to flying about, usually 

 ovipositing on the same tree they inhabited as larvae. There may be several thorn trees 

 not far apart, and one will be depredated on year after year till it is nearly destroyed, 

 while the others will remain untouched till colonized apparently by accident. The beetles 

 are sluggish, and when approached suddenly fall to the ground and quickly endeavour to 

 conceal themselves, not feigning death, as many insects under the same circumstances do ; 

 and when I say feigning death, I mean it literally, in opposition to an unsupported 

 dogmatic statement which I lately saw in print somewhere, " that insects can have no 

 knowledge of death." 



Oviposition is effected probably during the night, and the process has not been witnessed 

 nor the eggs seen. The limbs selected for this purpose vary from one-third to one and 

 one-fourth inches in diameter, and according to the thickness of the limb, the female with 

 her powerful mandibles makes from three to six longitudinal incisions through the bark, 

 each about three-fourths of an inch long and equi-distant and parallel to one another, 

 dividing the circumference into sections nearly equal ; an egg is placed in each end of 

 each of these slits, and as soon as hatched the larva makes a burrow beneath the outer 

 layer of wood, perhaps one-eighth inch in length at first, and uses this as a retreat whence 

 it issues to feed on the diseased wood caused by the incision. These slits and the irrita- 

 tion produced by so many larvse at work, cause an increased flow of sap to the part, and 

 a consequent thickening of the sections between the slits, so that the injured part soon 

 assumes a gall-like appearance. On the approach of winter, the larvae having now attained 

 the length of .25 inch, retire back a little further and close the opening of their burrows 

 with borings. One of the larvae, however, and in thick limbs two or three at each end 

 bore obliquely till one of them reaches the centre of the limb, up which it proceeds, often 

 two or three inches; the others parallel this, but keep a wooden partition between the burrows. 

 These larvae are much larger — often twice the size — of those inhabiting the outer wood, 

 and are the only ones that produce beetles. 



The whole of the interior of the limb is now dead wood enclosed by a growth of 

 living but unsound woody tissue, through which some openings remain. The limbs are 

 much weakened at these places, and many of them, like the oak on which Elaphidion 

 villosum depredates, would be broken off by the winter storms were the fibre not very 

 tough and the trees very low. And here analogy leads to the conclusion that as the 

 larva? inhabit the portion of the limb next the tree, equally with that beyond the injured 

 part, this is likely to be the case in the history of the Elaphidion mentioned. 



Many of the larva? in the outside wood perish during the winter, and the survivors, 

 after feeding a while in the spring, likewise die, their mission seeming to have been 

 merely to insure a sufficiency of dead wood to sustain the life of the favoured few destined 

 for full development. 



In the spring the larvae in the deep wood return and feed on the dead wood, which 

 is now abundant enough for all their wants, and by autumn they are nearly full grown 



