CHAP. XV.] 



ANTENNAE : BEETLE. 



413 



The number of antennary joints is employed as a specific character 

 in the classification of Lysiphlebus by Ashmead, Proc. U. S. Nat. Mus., 

 1888, p. 664). Coquillet, D. W., Insect Life, 1891, Vol. in. p. 313. 



*620. Donacia bidens. (Phyt.) A female found by Dr D. Sharp 

 at Quy Fen in company with many normal specimens had in each 

 antenna eight joints instead of eleven as in the normal. As shewn 

 in the figure (Fig. 123) the antennae of the two sides were exactly 



Fig. 123. Donacia bidens ? . I. Normal antennae, eleven joints in each. 

 II. Abnormal specimen, having eight joints in each antenna. No. 620. 



alike, and the insect was normal in all other respects. I am much 

 obliged to Dr Sharp for shewing me this specimen. 



Forficula auricularia, the common Earwig. In the various 

 species of Forficula the number of joints in the antenna? differs, 

 the numbers 11, 12, 13 and 14 being all found as normals in 

 different species 1 . As regards F. auricularia most authors give 

 14 as the number of antennary joints. Serville 2 gives 13 or 

 14. A number of adult earwigs examined by myself with a 

 view to this question shewed that there is great diversity in 

 regard to the number of antennary joints. The whole matter 

 needs much fuller investigation but the preliminary results are 

 interesting. 



The commonest number is 14, which occurs in perhaps 70 — 

 80 per cent. The next commonest is 13, which was seen in a 

 considerable number, while 12, and even 11 occur in exceptional 

 cases. Different numbers were frequently found on the two sides. 



1 Brunner von Wattenwyl, Prodr. eur. Orth., 1882. The number in F. auri- 

 cularia is given by Brunner as 15, but I have never seen this number. It is no 

 doubt an accidental error. The same mistake is repeated by Shaw, E., Ent. Mo. 

 Mag., 1888—89, xxv. p. 358. 



2 Suites a Buffon: Orthop., 1839. 



