[454 J 34 • 



crescences ou the leafless trees. This gall is the ^ork of the species 

 first described by Mr. Walsb, under the name of Byrsocrypta vagahnndus. 



Aijotlier species, which is the subject of the present article, forms the 

 swellings at the junction of tbe leaf-stalk with the leaf, often assuming 

 a reddish tint, and growing to the size of a small marble. Unlike the 

 former, this species is most abundant on the lowest branches, and pro- 

 bably always commences its operations upon this part of the tree. It 

 is a widely spread insect, and its bullet-like galls must have been often 

 observed, but very little has been recorded of its history. Mr. Walsh 

 refers to it incidentally in some of his able and elaborate Avritings upon 

 tlie gall-making insects ; and Dr. Fitch described and named it nmny 

 years previously, but evidently without having had an opportunity to 

 study its habits. Though not itself an insect of much practical import- 

 ance, its history has what may be denominated a generic value, in 

 consideration of its belonging to the gall-making division of the exten- 

 sive and important family of Aphides, and as helping to elucidate the 

 origin and growth of these curious excrescences. Indeed, the manner 

 in which the growth of galls takes place seems to be very imperfectly 

 understood. Dr. Fitch, in his brief sketch of the present species, quotes 

 from Mr. Reunie's "Insect Arcliitecture," an account of the manner in 

 which the gall of a closely allied European species is formed, reasonably 

 judging that all galls of the same general character, or which are made 

 by species of the same genus, are formed in the same manner. But Mr. 

 Eennie's exiilanation has very much the aspect of a closet theoiy, and 

 not a description founded upon actual observation. If insects could be 

 supposed to be endowed, for a brief period, with superior intelligence, 

 we can conceive that they would often be much amused at the theories 

 which we, their more pretentious fellow-creatures, i>ropoimd for the pur- 

 pose of explaining their works and ways. 



Mr. Reunie supposes that these galls are formed by an exudation of 

 sap caused by the punctures of the insects, which subsequently becomes 

 condensed and organized ; but an inspection of the gall now under con- 

 sideration, in its earlier stages, shows that it is lirst formed by a little 

 fold of tlie leaf wliich encloses the insect, and that its subsequent en- 

 largement is an excessive and abnormal growth of the surrounding tis- 

 sues. The lips formed by the meeting Qf the folds of the leaf never be- 

 come agglutinated, but remain in the form of a slit, like the mouth of a 

 l)urse, whi(!h can be drawn open, and through which the matured in- 

 sects ultimately escape. In the cases of certain other species of A^jhides, 

 such as the common species which infests currant leaves, the ii^ritation 

 of the bisects simply causes bulgings of the leaf with intermediate hol- 

 lows in which the insects repose. These corrugations might, therefore, 

 be regarded as incomi)lete or abortive galls. 



