§ 



be seen that the chitinous process is not used as an exca- 

 vating organ. 



Occasionally, larvae may be found turning over to lie on 

 their backs and nibbling the egg shell with the mandibles so 

 as to produce a transverse marking on it. What the object 

 of this operation is, is not clear. It is possible, however, that 

 it roughens that part of the interior of the egg shell and is 

 intended to get for the teeth of the chitinous process a better 

 grip. 



The tension on the egg shell exerted by the larva soon 

 reveals itself in minute folds radiating from the anterior and 

 posterior extremities of the egg shell (Fig. 7). There are also 

 shallow grooves produced by the teeth of the chitinous 

 process as they are moved forward or backward during the 

 course of larval adjustments. The force so exerted by the 

 chitinous process may be so great as to rupture the egg 

 shell. This break is usually observed in the region of the 

 greatest convexity of the egg and through it meal from the 

 excavation may also be seen to come out. 



There has been some obscurity in the past in regard to 

 the function of the chitinous process. Riley^ was the first to 

 draw attention to this structure in the post-embryonic larva 

 of B. faboe. After describing the larva at length he pro- 

 ceeds,: — 



" We are not aware that similar structural peculiari- 

 ties in the first larval stages of Bruchus have been pointed 

 out before. They seem to indicate, perhaps, affinities with 

 Chrysomelidse and are evidently of advantage in aiding the 

 young creature in the work it has to do. This stage is very 

 evanescent. Immediately after finding the proper spot for 

 entering the bean, the larva gnaivs its way in and 

 moults.'' 



The description, while it does not disclose the function of 

 the chitinous process, attributes the actual excavation to the 

 jaws. 



Chittenden^ is even less clear in regard to the allocation of 

 functions. Apparently following Kiley, in describing the 

 same larva, he states " that both plates and legs are evanescent 

 but they assist the larva in obtaining the entrance into the 

 seed.'' Chittenden figures the chitinous plates for each of 

 the other species he describes but has not made any state- 

 ment in regard to it in these either. There is, however, little 



. - Riley. Insect Life, Vol. IV. Page 300. 



. Chittenden. Yeir Book of tha D3pirtm3nt of Agriculture, 1898, Page 236, 

 Footnote No. 2. 



