GALLS CAUSED BY SAW-FLIES 
J 9 
ing that it was given them to enable us easily to observe 
their marvellous operations. The sexes appear to be equal 
in only a few species. As a rule, the females are far more 
numerous than the males, and in some species males are 
unknown, parthenogenesis being frequent. For details 
concerning the habits of these most interesting insects the 
reader should consult Cameron’s “ British Phytophagous 
Hymenoptera,” from which invaluable work I have taken 
the following paragraphs concerning the gall - causing 
species : 
“ So far as my observations go, I do not find any marked 
difference in the mode of oviposition of the gall and non¬ 
gall-making saw-flies. I have noticed with some of the 
latter incipient gall formation following oviposition. No 
doubt the distinction between the two lies in the fact that 
the former brings its eggs in contact with the cambium 
layer, the latter not.” 
“ Unlike what happens with a cynips, the saw-fly gall is 
fully formed before the larva leaves the egg, so it is clear 
that the larva can have nothing to do in setting the gall 
growth in motion ; while in the cynipidae no gall commences 
to form until such time as the larva quits the egg and com¬ 
mences to feed. The cynips larva, again, feeds on a 
particular layer of the gall—namely, that part which im¬ 
mediately surrounds itself, and which contains a large 
quantity of starchy matter. They feed up also very rapidly. 
The saw-fly larvae consume every part of the gall, which 
does not contain a special layer of nutriment, all the gall 
(except, perhaps, the outer skin) affording nourishment. 
They do not either feed up in a few days, like most 
cynipidae; they are not, indeed, any more rapid feeders 
than other larvae. In their general habits and mode of 
forming the cocoon they do not differ from their congeners 
which feed openly.” 
“ The structure of the saw-fly galls is, except in the case 
of the woody galls of Enuvapentandrcie, very uniform. They 
are composed of irregular cells, the ordinary cellular struc- 
