50 Extraordinary Instincts peculiar 



of the blood in the Italian flying glowworm (iampyris italica) 

 and the luminous substance which occupies great part of the 

 under side of the abdomen. When he first noticed this in- 

 sect, which is so distinguished an ornament of an Italian 

 evening, 'he was much surprised to.find, what, strange to say, 

 no previous observer has described, that the light kept every 

 instant varying in intensity, being alternately much brighter 

 than ordinary; as the flame of a candle behind a shade of 

 horn would appear, if the seeds of Lycopodium were from 

 time to time thrown into it : and, after a series of experiments, 

 he ascertained that this phenomenon entirely depends on the 

 circulation of the blood; the greater intensity of light cor- 

 responding precisely with each pulsation of that fluid ; taking 

 place from forty-four to fifty-four times a minute, and at re- 

 gular intervals, when the insect was not disturbed, but more 

 rapidly and irregularly when it was alarmed on being first 

 caught.* 



The above discoveries of Dr. Cams suggest many topics 

 of investigation highly interesting to the entomological and 

 general physiologist, but into these I cannot attempt to enter ; 

 the only object of this hasty notice, written on the eve of a 

 long journey, being to draw the attention of British entomo- 

 logists to a field of enquiry equally extensive and important, 

 and in which, even if they detect nothing new, they cannot fail 

 to be highly gratified with observing what Dr. Cams has 

 already described. For a full account of the discoveries of 

 this celebrated physiologist I must refer your readers to the 

 forthcoming new edition of his Entdeckung eines Einfacheny 

 Vom Herzen aus beschleunigten Bhithreislaufes in den Larven 

 netzflilgeliclier Insekten, which first appeared in 1827. 



I am. Sir, &c. W. Seence. 



Dresden^ Aug. 28. 1829. 



Art. XII. On the extraordinary Instincts peculiar to some of the 

 Insect Tribe. By T. H. 



Sir, 

 Although the subject I have the pleasure to offer to your 

 notice is not new to naturalists, still you may, I think, consider 

 worthy of a place in the pages of your very amusing and instruc- 

 tive Magazine, a detail of facts which afford exemplifications 



* Analecten zur Naturwissenschaft und Heilkunde, gesammelt auf einer 

 Reise durch Italien, im Jahre 1828 (Dresden, 1829, 8vo), p. 169—179. 



