50 Extraordinary Instinets peculiar 
of the blood in the Italian flying glowworm (Lampyris itélica) 
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 Ly copodium 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. Carus suggest many topics 
of investigation highly interesting to the entomologica and 
general phy siologist, but into fiiece T cannot attempt to enter ; 
the only object of this hasty notice, written on the eve of ‘ 
long j journey, being to draw the attention of British entomo- 
logists to afield of enquiry equally extensive and important, 
and in which, even if they detect nothing new, they cannot fail 
to be highly gratified with obser ving aha Dr. Carus 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 Einfachen, 
Vom Herzen aus beschleunigten Blutk reislaujes an den Larven 
netzfliigelicher Insekten, which first appeared in 1827. 
I am, Sir, &c. W. SPENCE. 
Dresden, Aug. 28. 1829. 
Arr. XI. On the extraordinary Instincts peculiar to some of the 
Insect Tribe. By T. H. 
Sir, 
Aanwtouen the subject I have the pleasure to offer to your 
notice is not new to naturalists, still you may, I think, consider 
worthy ofa 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. 
