THE AMEmCAN ENTOMOLOGIST. 



71 



kiuii or other of gall-makers, and cannot there- 

 fore be physically incapable of bearing galls. 

 The reason is simple. Their ancestors inhabited 

 some kind or other of Oak in some old Palasozoic 

 epoch millions of years ago, and by the Laws 

 of Inheritance transmitted the same habit to 

 most of their descendants. Upon the same 

 principle the progeny of the ancient black race 

 of men that inhabited Etliiopia in the days of 

 the Pharaohs, is found in that very same region 

 up to the present day . 



Which of the above two explanations of a 

 most curious and intci-esting phenomenon be 

 the more rational or intelligible, our readers 

 must judge for themselves. 



/, 



The Wool-sower (Jail. 

 {Qiiercus scminafor, Harris.) 



The three "Willow galls produced by Saw- 

 flies, that we have already treated of in this 

 Article, are all " monothalamous." The two 

 Oak-galls that we are now about to describe are 

 both of them " polytbalamous " or many-celled ; 

 that is, each gall contains an indefinite number 

 of distinct cells, each of which is inhabited by 

 a single gall-making larva. In the "Wool-sower 

 gall (Fig. 45 a, sectional view), these cells 



[Fig. 45.] 



Color— Liglit buff, 



may be seen in the middle of the gall, and 

 are little pip-like bodies having much the ap- 

 pearance of a canary-seed, one of which we 

 represent enlarged at b, so as to show the hole 

 through which the perfect fly has made its exit. 

 The reader can form a tolerably good idea of 

 the shape and make of this fly, by refei'ring to 

 the drawing given in our first "Volume (page 

 104, fig. 81) of au allied gall-fly, which however 

 is thrice as large and which difters further from 

 the "S\^ool-sower Gall-fly by the wings being 

 much marked with brown-black. 

 The "Wool-sower gall is met with exclusively 



on the "White Oak, and like the Oak-fig Gall to 

 which we formerly referred (Vol. I. p. 101) is, 

 not a bud-gall, but a true twig-gal!, growing 

 early in the spring out of the bark of the twig 

 itself. Mr. Bassett (Proc. Ent. Soc. Phil., 11, 

 p. 331) broaches the theory that the "Wool-sower 

 gall and Osten Sackcn's Q. operator gall are 

 not twig-galls, but true bud-galls, and that 

 " their cells arc modified leaves, the silky fibres 

 covering them being only a monstrous develop- 

 ment of the pubescenci^ always observable on 

 young leaves." But 1st: As to the Oak-fig 

 gall, we have already recorded the fact that 

 '■ this mass of subglobular galls about the size 

 of peas is clustered densely around the infested 

 twig, loithout in any wise interfering with the 

 no7-mal development of the buds." {Ibid. VI. 

 p. 275.) "We may remark by the way that we 

 have recently found the Oik-fig gall upon un- 

 doubted Bur Oak {Q. macrocarpa) , although 

 it had been i)reviously supposed that it never 

 occurred except on "White Oak (Q. alba). 2d: 

 As to the Q. operator gall, we ascertained 

 long ago that it is a deformation, not of the 

 twig, nor of the leaf-buds, but of the male 

 flower of the species of Oak, upon which alone 

 we have hitherto met with it, namely the Black 

 Oak (Q. iinctoria); for the Black-jack Oak 

 (Q. nigra), upon which Osten Sacken first dis- 

 covered it, does not grow in North Illinois. 

 Even on this last oak Osten Sacken records the 

 fact that his gall occurred exclusively ''on 

 young flowering branches. ■■ (J bid. I. p. 266). 

 3d: As to our "Wool-sower gall, if the cells 

 were a deformation of the buds, we should 

 surely find them gathered into two distinct 

 groups around the bud on each side of the oak- 

 twig that gave origin to them, as in the gall 

 which is next to be noticed; whereas they arc 

 always evenly distributed around the axis of 

 the twig. Besides the pip-like cells to which 

 we have already referred, it is composed of little 

 else but a mass of whitish, spongy wooly mat- 

 ter, the external surface of which is of a pretty 

 rose-color early in the season, but towards the 

 middle of the summer assumes a rusty brown 

 shade. At every period of the year the outside 

 of the gall is invariably studded with numerous 

 conical projections or teeth, which are veiy 

 characteristic, though our engraving scarcely 

 shows them as pointed as they arc in nature, 

 and Dr. Fitch's figure omits them entirely. The 

 perfect Gall-fly comes forth about the end of 

 July, and the female must then, after coupling 

 with the males, puncture such "White-oak twigs 

 as she judges to be suitable for her purpose in 

 a very great number of adjoining points, drop- 



