THE VOYAGE OF THE BEAGLE 41 



bers: they resembled in general form the female of the 

 English glowworm. These larvae possessed but feeble lumi- 

 nous powers; very differently from their parents, on the 

 slightest touch they feigned death and ceased to shine; nor 

 did irritation excite any fresh display. I kept several of 

 them alive for some time : their tails are very singular organs, 

 for they act, by a well-fitted contrivance, as suckers or organs 

 of attachment, and likewise as reservoirs for saliva, or some 

 such fluid. I repeatedly fed them on raw meat; and I in- 

 variably observed, that every now and then the extremity 

 of the tail was applied to the mouth, and a drop of fluid 

 exuded on the meat, which was then in the act of being con- 

 sumed. The tail, notwithstanding so much practice, does not 

 seem to be able to find its way to the mouth ; at least the neck 

 was always touched first, and apparently as a guide. 



When we were at Bahia, an elater or beetle (Pyrophorus 

 luminosus, Illig.) seemed the most common luminous insect. 

 The light in this case was also rendered more brilliant by 

 irritation. I amused myself one day by observing the spring- 

 ing powers of this insect, which have not, as it appears to 

 me, been properly described. 5 The elater, when placed on 

 its back and preparing to spring, moved its head and thorax 

 backwards, so that the pectoral spine was drawn out, and 

 rested on the edge of its sheath. The same backward move- 

 ment being continued, the spine, by the full action of the 

 muscles, was bent like a spring; and the insect at this mo- 

 ment rested on the extremity of its head and wing-cases. 

 The effort being suddenly relaxed, the head and thorax flew 

 up, and in consequence, the base of the wing-cases struck 

 the supporting surface with such force, that the insect by 

 the reaction was jerked upwards to the height of one or 

 two inches. The projecting points of the thorax, and the 

 sheath of the spine, served to steady the whole body during 

 the spring. In the descriptions which I have read, sufficient 

 stress does not appear to have been laid on the elasticity of 

 the spine : so sudden a spring could not be the result of sim- 

 ple muscular contraction, without the aid of some mechanical 

 contrivance. 



On several occasions I enjoyed some short but most pleas- 



6 Kirby's Entomology, vol. ii. p. 317. 



