APPENDIX. 



39' 



renoe on over thirty dilTerent plants in Europe. Certain stone fruits and the 

 pear, jjarticularly the latter, are their especial favorites. 



LIFE-HISTORY AND HABITS. 





T .-'^^^^^^^'^^'^^r^ 



jv#.~ 



Fig 



C 



2 — Pear sluff, illustrating mothf)d of oviposi- 

 tion and oiiiergeiice of larva; a, cutting of cell 

 beneath epidermis, with ovi^wsitor; h, same after 

 e;jg has been deposited; c, same after escape of 

 larva — enlarged (original). 



The parent fly may be seen on the pear or other trees which serve as food 

 for the larvfe very early in the spring-. In Washing-ton, D. C, the present 



season they were observed on 

 the newly-expanded leaves by 

 the middle of April actively 

 engaged in laying their eggs. 

 In the latitude of Boston and 

 northward the flies do not ap- 

 pear much before the middle 

 of May, and the egg-laying is 

 chiefly during the latter part 

 of May and the first of June. 

 Judging from our experience 

 here many of the eggs laid by 

 the flies which appear in April 

 perish during the cold, wet 

 weather which often charac- 

 terizes this month. This was 

 the case the present season, 

 few. if anv. of the eggs first 

 deposited producing larvse. 

 But one egg is doposited in a place, and it is always inserted from the 

 under side of the leaf. The ovipositor is thrust obliquely through the leaf 

 to the upper epidermis, but not piercing the latter, and shows there dis- 

 tinctly through the transparent upper skin of the leaf, as represented in the 

 accompanying illustration (Fig. 2), while the insect otherwise is completely 

 hidden. The saw-like instrument, when brought into the position noted, 

 is moved rapidly with a swinging lateral motion from side to side, cutting 

 the upper epidermis free so as to form an irregular cell or pocket of peculiar 

 flattened ovoid outline. The egg is quickly passed down between the plates 

 of the ovipositor and dropped into the pocket thus made, the time occupied 

 being a little over one minute for the entire oj^eration. 



Usually before^placing the egg the fly runs about rapidly over the upper 

 surface of the leaf, examining it carefully, and then goes over to the under 

 side to insert an egg, after which she reappears on the upper surface of the 

 leaf and rests for a minute or so before flying to another leaf. 



It often happens that a good many eggs are deposited in a single leaf, but 

 I am convinced that this is usually by different flies or at dift'erent visits by 

 the same individual. The loosened epidermis about the egg dries some- 

 what, and the egg-cell soon appears as a minute brownish spot with the 

 almost colorless egg showing at the center. The egg is oval, slightly 

 flattened on one side, and remains in its peculiar cell (see Fig. 2, b) for a 

 period of about twojweeks before the larva escapes. It is so placed in the 



