December, 1883.] 145 



SOME FURTHEE OBSEEYATIONS ON THE PARTHENOGENESIS OF 

 ZARMA FASCIATA, AND ON THE EMBRYOLOaY OF THAT 

 SPECIES AND OF SU3IIA CRATJEaATA. 



BT J. A. OSBOENE, M.D. 



During the past summer I have coutiiiued my observations on 

 Zar(sa fasciata, and confirmed most of those of which an account was 

 given in this Magazine, in the number for Oct., 1882 (p. 92). Before 

 passing to points of fresher interest, I wish first to mention some facts 

 newly noticed, which modify or extend particular statements in my 

 last paper. And to take them in the order in which they there occur, 

 I have to say, in the first place, that the colour of the cocoon is in- 

 fluenced by the food. The " dark brown (resinous-looking) cocoons " 

 are made by larvae fed on snowberry leaves alone ; whilst those whose 

 sole or chief diet is honeysuckle make cocoons mvich lighter in colour, 

 pale dirty greenish, which, though they look slighter seem to be not 

 less efiicient than the others. When comparing the great difference 

 in size of the full-fed larvae to that of the larvae of Nematiis rlhesii, 

 my supposition at the time was, that the smaller larvae might yield 

 male flies next season. This supposition did not prove correct. I 

 have noticed differences of size in the ratio of about 2 : 1 in the fresh- 

 laid eggs, in the newly -hatched larvae and larvae full-grown, and in the 

 flies themselves, without any difference of sex. The peculiar bands 

 connecting the saw with its back were the subject of some corres- 

 pondence with a gentleman in Eton, and I think it right now to state 

 that I have not since been able to procure any separation of the saw 

 from its back or sheath, without at the same time bringing away these 

 processes, in the form of little tufts or brushes adherent to the latter. 

 Their connection with the saw itself appears to be extremely slight, 

 and their nature and use I cannot conjecture. 



Besides steadying the leaf with the apical spines of the posterior 

 tibiae when about to insert its ovipositor, the fly further makes use of 

 the hinder angles of the valves (with which it subsequently pinches 

 and closes the orifice), to hold the leaf firm at the very point where 

 the extremity of the saw is to be first introduced. The mine is mostly 

 beneath the upper surface, but instances are not infrequent in. which 

 it is found immediately under the lower cuticle. 



Last year I was not able to say positively in which end of the egg 

 the head of the embryo develops. As the result of numerous 

 observations I am now in a position to state, that the head of the 

 embryo is found in the upper and the lower pole of the egg with about 



