334 ARACHNOIDEA. 



CASE gall j whereas, wherever Phytopti do occur, it is not in single file, 

 but in battalions. Besides, they are so very small that we doubt 

 very much, if only one were put inside a nail-gall, whether 

 we could find it again in such a comparatively spacious hall 

 Moreover he speaks of the cottony hairs filling up the interior. 

 It is true that, where he does so, he is speaking of his inefi'ectual 

 search for them, and its absence may have escaped his notice 

 when he found the grub ; but if phytopti were feeding in the gall, 

 the hairs would have been mowed down. We never saw hairs, or, 

 at all events, long crowded hairs, or indeed anything but their 

 remains, in mite-galls in which Phytopti were present ; and we 

 saw Phytopti in mite galls in which hairs were abundant. 



We may also in passing correct the misconception which 

 Reaumur has expressed as to a crack taking place in the gall. 

 Strictly speaking, the mite-galls are not galls in the sense of 

 being enclosed portions of vegetable tissue in the midst of which 

 the larva lives. They are merely abnormal thickened growths of 

 a portion of the leaf; and the thickening being unequal, usually 

 greatest on the upper side of the leaf, it there expands like a 

 round gall while the under side is drawn up in the interior like 

 the open mouth of a purse. By this character, mite-galls ctcH 

 always be known : they always have an opening leading into them, 

 and generally from the under side or margin of the leaf. The 

 importance of this distinction will be more evident when it is 

 remembered that there is nothing to hinder galls made by other 

 insects from assuming a form similar to the growths caused by 

 mite-galls ; and, in point of fact, some of them are remarkably 

 alike : for example, we have above given a figure of the lime-leaf 

 covered by nail-galls made by a mite ; and here is that of a North 

 American vine-leaf covered by similar nail-galls (called by American 

 entomologists the trumpet grape gall) made by a Cecidomyia (a 

 small gnat-like fly). They look identical, and any one would 

 naturally expect that they were both made by a like architect ; 

 but sections of them respectively show that the former has an 



