592 



NEW VORK STATE MUSEUM 



color, without marking's, and cylindric, except as its shape is modified by 

 pressure of the wood and adjacent eggs. The )oung resemble the adults 

 but are wingless and armed along the dorsal line with numerous forked or 

 barbed projections. The adiilt is a green insect, about 3^ inch in length, 

 and may be easil)' recognized b\' the greatly enlarged thorax which bears 

 on its anterior angles lateral projecting horns, as represented in figure 148. 

 Life history. The life history of this insect has been given by Mr 

 Marlatt substantialh' as follows : 



The adult insect deposits her eggs in twigs 

 of various trees, preferably those of two or three 

 _\ears' growth. particularl\- the apjjle, willow, Cot- 

 tonwood, maple t;tc. and confines its operations 

 in general to the upper surface of the twigs. It 

 2u' llA !^^-^W works more abundantK' on the south side of 



the trees than on the north, though in this 

 respect the prevailing winds and other con- 

 ditions appear to ha\e an influence. The eggs 

 are depositetl (piite as n\ulil\' m the new growth 

 of oUl trees as in \x)ung growth though the tlam- 

 age is much more noticeable in the latter. They 

 are placed in small com|)ound grou])s of from 

 tures; .-bark six to 12 eggs, each arrani/ed in two nearly 



ition, slightly '^^ '^ -' 



parallel or slightl\- curved slits extending in the 



-female 



I- i,«. i<9 Twij; of :iDple slio 

 at work; /.=recciit ejjg pu 

 reversed with ej;gs iti position 

 enlarged ; ,/_single mw of ecgs still 

 enlarged ; /"^wounds of two or 



years' siaitdinR on older limbs. 'After (Ijrection of the twlg about .',6 iucli, aiul sei)a- 



Marlalt, U. S. Dep'l .Agric. Div. lint. 1897 '^ ' 



c'"- '3< ^'i ^■'> rated b)- Vg inch or less of l)ark. The bark is cut 



by the ovipositor in such a way when de])ositing the eggs that the narrow- 

 portion inter\ening between the two incisions is loose. This has a \cvy 

 important bearing on the subse(|uent condition of the wountls made 1)\- the 

 insect in oviposition. The object is doubtless to cause a deadening o( the 

 wood between the two rows of eggs, and thus i:)revent their being crushed 

 or choked by the subsequent ra|)id growth o.f the twig, and it is due to this 

 peculiarity that the injury later assumes such a serious nature. A single 



