118 VARIETIES. 



latter, which was more abundant than the PlatymiscJnis, runs 

 very fast ; and, when touched, contracts its antennae and legs, 

 and lets itself fall from the rocks. At Plymouth it was much 

 rarer ; I saw only one or two specimens. 



F. Walker. 



8. Chnjsomela graminis. — Sir, This insect appears to be 

 double-brooded : I find it in a wet place near this city (Bath), 

 upon the Mentha hirsuta, to which plant it appears very 

 strictly to confine itself, in the middle of June and the be- 

 ginning of September. It is in great plenty at both the above 

 times ; but I do not remember finding a single individual 

 during the intervening months. My friend, the Rev. F. Lockey, 

 observes, that in the autumn it feeds upon the flowers of the 

 Mentha in preference to the leaves. 



C. C. Babington. 



9. Cardiapus Mathewsli. — I found this insect in great 

 plenty (taking more than forty specimens,) on the Cis/its 

 Helianthemiim, at the top of the Gogmagog Hills, near Cam- 

 bridge, on the 4th of last July, and also on tlie same plant, but 

 in smaller quantity, at the Devil's Ditch, Newmarket Heath, 

 on the 2d of that month; at both these places many other 

 specimens were also taken. 



Yours, &c. C. C. Babington. 



Balk, Nov. 5, 1833. 



10. Ignis Fatuus. — The supposition, that the Ignis fatuus 

 is caused by the light emitted by some insect has, I believe, 

 among scientific men, long yielded to the known fact, that it 

 is merely the combustion of gaseous matter. In a very inte- 

 teresting paper upon this subject in a former number of your 

 Magazine, the facts and experiments related prove this latter 

 theory beyond doubt ; but the writer leaves us in the dark as 

 to the nature of the gas to which the phenomenon is attri- 

 butable. 



This gas, however, I believe, is generally supposed to be 

 phosphuretted hydrogen, a combination of phosphorus and 

 hydrogen gas, which spontaneously ignites upon coming in 

 contact with atmospheric air. Should any of your readers 

 feel inclined to illustrate this by actual experiment, or to view 



