10 BRITISH CICADiE. 



during which operation no hght appears, but it is 

 immediately evoked by moistening the powder with 

 water. 



Dr. Dubois thinks that the action is more of a 

 chemical than of a nervous nature, — that is, action 

 evoked by nervous excitability, — and that an albu- 

 menoid substance exists which is acted on by a 

 matter belonging to a chemical diastase group, during 

 the combination of which secretions, light is liberated. 

 {ride 'Ent. Month. Mag.' vol. xiii., p. 143; also 

 ' Nature,' vol. xxxiv., p. 578.) 



Some Fulgoridffi attain to considerable dimensions 

 in semi-tropical countries, but in Northern Europe 

 they are represented only by comparatively small, yet 

 numerous, species. Probably Issus is the largest 

 representative yet known in Britain. 



III.— TETTIGOMETRID^. 



Numerous in Central Europe, but represented in 

 Great Britain by only a single species. 



Genus I.— TETTIGOMETRA, Latr. 



Easily recognised by the peculiar form of the 

 antennae, and the position of the seta upon it. Also 

 by the horny and punctured elytra, rising from distinct 

 tegulae. " Face ptyloid." — Edw. 



Tettigometra impresso-punctata, Sign. 

 Plate III., figs. 10 to 12. 



Tettigometra impresso-punctata, Sign., Marsh, Fieb. 



C.^E., pt. ii., 130 ; Edw., p. 48. 

 T. frontalis and T. fasciata, Fieb. 

 T. nitidula, Kirschb. 



Face without keels or carinse, swollen. Antennae 

 placed near the base of the eyes, and just under the 

 ocellus, which last is situated at the inferior margin of 

 the eye. First antennal joint half the size of the 



