138 



casual observer who depends on this character alone is liable to be mis- 

 led, as there is another species of saw-fly Harpiphorus maculatus (Nor.)J 

 closely resembling it, and having similar markings on the back of the 

 abdomen. The most certain method of distinguishing the two species 

 is to note the number of submarginal cells in the fore wings, M. ignota 

 having four, and H. maculatus only three. 



The larvae of M. ignota have infested the strawberry beds on the col- 

 lege grounds for several years, feeding on the leaves, and would, if 

 numerous enough, threaten the crop. This has not been the case here, 

 but reports from other parts of the State say that " the worms are sim- 

 ply ruining our plants." Drawings of this species in all its stages are 

 given in Fig. 22. 



Adult saw-flies of this new strawberry pest were found depositing 

 eggs from the 1st to 25th of April, the period of greatest deposi- 

 tion being from the 10th to 20th. Adult females were captured, con- 

 fined, and eggs obtained that have furnished larvae which have been 

 carried through all the larval stages and their habits studied in con- 

 nection with observations in the field. The eggs are deposited singly 

 on the under side of the leaf, just beneath the epidermis. In no case 

 were the eggs found deposited in the petiole of the leaf as is said to be 

 the habit in H. maculatus, but frequently alongside or in the angle be- 

 tween two veins ; seldom more than three or four eggs are found de- 

 posited in a single leaflet. 



When first deposited the eggs (Fig. 22a) are pure white, tapering 

 towards both ends, one side slightly concave, the other quite convex ; 

 are .475 mm wide by .875 mm long. The point of deposition can hardly 

 be seen at first, but the swelling of the eggs, due to the developing 

 embryo, causes light-colored blisters of 0.5-.75 by .7o-l mm in size. Dur- 

 ing embryonic development the transverse diameter of the egg is doubled 

 or trebled, lengthens about one diameter but does not thicken much. 

 In Fig. 22 are shown a few of the more important changes taking place 

 during the embryonic growth of the larvae. Its embryology has been 

 traced in detail, but only a suggestive outline can here be given. 



First. Segmentation of the yolk and partial differentiation of the 

 anterior and posterior embryo lobes. Fig. 22 o. 



Second. Division of the anterior lobes and the differentiation of the 

 ventral surface which at this stage occupies the outer circumference. 



Third. The folding of the embryo upon its ventral surface and the 

 differentiation of the two lower anterior lobes. Fig. 22 r. 



Fourth. Beginnings of the alimentary canal; anteriorly, the oesopha- 

 gus; posteriorly, the rectum and colon. Fig. 22 r. 



Fifth. Continued development, forming the remainder of the aliment- 

 ary canal; appearance of the eye-spots and muscles of the head and 

 mouth parts. Fig. 22 s. 



X Emphytus maculatus (Nor.). Boat. Proc, VIII, 1861, pages 157, 158. Trars. Am. 

 Ent. Soc, I, page 232. 



Harpiphorus maculatus (Nor.). Cresson's Synopsis N. Am. Hymen., page 160. 



