of certain specks of Willow. — Part 2nd. 275 



ls^. Certain Willow Gall-gnats, which can be readily distinguished by 

 the galls produced by them, are undistinguishable, as I have shown at 

 great length, in all states of the insects themselves. 2nd. The gall 

 caryxcaulis, Fitch, grows on the upper surface of the leaf-stalk of a 

 Hickory, (or sometimes, as is correctly stated by Fitch, upon the young 

 succulent twigs of the same year's growth,) and opens above when 

 ripe, to allow the Plant-lice which it contains to escape, by a slit that 

 is usually decussated, or in the form of a 4- ; and this gall often attains 

 quite a large size, say fully | inch in diameter. On the other hand 

 the gall carj/seglobuli Walsh grows on the leaflet of the same Hickory, 

 and when ripe, opens below, not above, and always by a simple longi- 

 tudinal slit, as is the general, though not the universal rule in Aphidi- 

 an galls, carysefolise, for instance, opening above at the apex of the 

 conical figure which it presents on the upper surface of the leaflet; 

 and this gall — carj/se globuli — never exceeds ?or| the extreme diame- 

 ter of cari/secaulis. Yet the Phylloxera* produced from these two very 

 distinct Hickory galls are absolutely undistinguishable, either by size, 

 shape, structure or coloration, even when numerous specimens of each 

 are placed side by side. (Proc. etc. II, p. 462.) It may be thought, 

 perhaps, by those who do not know how constant and invariable a 

 thing a Gall is, and how definitely all its characters are determined by 

 the insect which gives origin to it, that the same insect produces in 

 this particular case a different gall, according to the location of that 

 gall, whether on the stem of the leaf or on the blade of the leaflet. 

 But — not to rely exclusively on the fact, that carysecaidis galls located 

 on the twig are precisely like those on the leaf-stalk — there is another 

 remarkable example, which shows that this can scarcely be so. The 

 Cynipidous gall Q. ficus Fitch is, not a bud-gall generated by the 

 deformation of a bud or buds, but a true twig-gall, a mass of subglo- 

 bular galls about the size of peas being clustered so densely round 

 the infested twig, without in any wise interfering with the normal de- 

 velopment of the buds, that, except on the outskirts of the mass, they 

 usually press against one another so closely as to become each 3, 4 or 

 5-sided. In fact, to make use of Dr. Fitch's graphic comparison, from 

 which he derived his specific name, they closely resemble a mass of 

 round figs, pressed together in the box in which they are packed so as 

 to become many-sided instead of mimd. Now I have noticed five or 

 six instances, where the mother insect, when depositing her eggs with 

 the accompanying drop of poison in November towards the tip of a 



- Respecting this genus, see the note a few pages below. 



