230 Benj. D. Walsh on the Insects inhabiting the Galls 



Mr. Norton, although he fully recognizes the fact of the supposed 

 1st abdominal joint being metathoracic, and calls it in his descriptions 

 sometimes the " basal plates" and sometimes the "basal membrane/' 

 yet has assumed the existence of an imaginary 1st abdominal joint, 

 " which is often concealed by the basal plates of the metathorax," so 

 as to make up the full number of 9 abdominal joints.* Any one, how- 

 ever, can readily see that this imaginary 1st joint is not found in nature ; 

 and some of Mr. Norton's descriptions, in consequence of this recog- 

 nition of a nonentity, are difficult to understand. For example, in 

 Tenthredo W-punetata Nort. we read "a broad stripe through the 

 middle of 7 basal segments of abdomen, and seven dots [one dot ?] 

 on each side near the base of each, black." (Proc. Eat. Soc. Phil. I. 

 p. 143.) Is the imaginary 1st abdominal joint included in these " 7 

 basal joints," or is it not? And if it is, does it bear a broad dorsal 

 black stripe and a black dot on each side ? The truth of the matter. 

 I suppose, is, that this author has mistaken what I call the " basal 

 membrane" for a rudimental 1st abdominal joint. But as this " basal 

 membrane" is no part of the external horny skeleton, and is always, 

 so far as I have observed, of a homogeneous color, it can scarcely be 

 marked in the manner inferred by the above description ; and most 

 probably it is the 7 basal segments in the Westwoodian sense, not the 

 7 basal segments in the Nortonian sense, that are in reality striped and 

 spotted with black in Tenthredo 14-pvnctata. Moreover not only does 

 Mr. Norton somewhat incongruously use the terms •• basal plates," and 

 "basal membrane" as synonymous, (Proc. B. S. N. II 1860, pp. 237, 

 240, 241, 242, 244, 246, 248, 250, 253, &c.,) but he repeatedly de- 

 scribes the true "basal membrane" as a spot on the 1st abdominal 

 joint; (ibid. 1861, pp. 159, 160, 161, &c.;) whereas in reality it 

 forms no part whatever of any abdominal joint, but simply connects 

 the metathorax with the abdomen, and like most other connecting 

 membranes is not spotted, but of a uniform color. 



• Proc. Bost. Soc. Nat. Hist. 1862, p. 117 note, and compare the description of 

 Allantus dubius, ibid. 1860 p. 241, where he speaks of " the fifth, seventh, and 

 two apical segments of the abdomen,'' and that of Tenthredo semiruf us, Proc. 

 Ent. Soc. Phil. III. p. 12. Strictly speaking, these "basal plates" ought to be 

 called ••terminal plates :" for they are placed at the tip, not at the base, of the 

 metathorax, the anterior end of the mesothoracic scutel being generally in 

 Insects considered as the centre nf polarity. But it is better to use an estab- 

 lished phrase, even though it be somewhat incorrect, than to create confusion 

 by changing it. Probably the original author of the term considered the 

 ••basal plates" as appertaining to the abdomen : and of course, in regard to the 

 abdomen, they are really basal. 



