148 APPENDIX. 



acquainted with the means of preventing in future so great a 

 calamity. 



Lest the flies may become disfigured in travelling, it may be 

 prudent to say that their wings are four ; that their antennae are 

 clubbed, and about one-third the length of their body, each be- 

 ing composed of nine joints, namely, two next the head, above 

 which two there is a joint somewhat longer than the rest, and 

 above this six more joints, similar to the two below ; that near 

 the point of the tail of the female there is a black speck, out- 

 wardly fringed with hair, but which, opening longitudinally, ap- 

 pears to be the end of a case, containing a delicate point or 

 sting, about one-twentieth of an inch in length, which on a 

 cursory view appears to be a simple, lanceolated instrument, 

 with a strong line passing down the middle, and serrated at its 

 edges, but on a closer inspection, and by agitating it strongly 

 with a point of a needle, it separates into three one-edged in- 

 struments, hanger-like as to their general form, with a spiral 

 line or wrinkle winding from the point to the base, making ten 

 or twelve revolutions, which line, passing over their edges, gives 

 them some appearance of being serrated. 



By the help of these instruments, I apprehend, the female 

 deposits her eggs in the edge of the turnip-leaf (or sometimes, 

 in the nerves or ribs on the under surface of the leaf) ; thus far 

 I can say, and I think with a considerable degree of certainty, 

 that having put some fresh turnip-leaves into a glass containing 

 several of the male and female flies, I perceived (by means of a 

 simple magnifier) that one of the females, after examining atten- 

 tively the edge of the leaf, and finding a part which appeared to 

 me to have been bitten, unsheathed her instruments, insinuated 

 them into the edge of the leaf, and having forced them asunder, 

 so as to open a pipe or channel between them, placed her pubes 

 (the situation of which from repeated and almost incessant 

 copulations I had been able to ascertain precisely, and to the 

 lower part of which these instruments seem to be fixed) to the 

 orifice, and having remained a few seconds in that posture, de- 

 liberately drew out the instruments (which the transparency of 

 the leaf held against a strong light afforded me an opportunity 



