The Glow-Worm and Other Beetles 



instinct derived from the organ, or is the or- 

 gan instinct's servant? An old dead cherry- 

 tree will answer our question. 



Beneath its ragged bark, which I lift in 

 wide strips, swarms a population of larvae 

 all belonging to Cerambyx cerdo. There are 

 big larvae and little larvae; moreover, they 

 are accompanied by nymphs. These details 

 tell us of three years of larval existence, a 

 duration of life frequent in the Longicorn 

 series. If we hunt the thick of the trunk, 

 splitting it again and again, it does not show 

 us a single grub anywhere; the entire popu- 

 lation is encamped between the bark and the 

 wood. Here we find an inextricable maze 

 of winding galleries, crammed with packed 

 sawdust, crossing, recrossing, shrinking into 

 little alleys, expanding into wide spaces and 

 cutting, on the one hand, into the surface 

 layer of the sap-wood and, on the other, into 

 the thin sheets of the inner bark. The po- 

 sition speaks for itself: the larva of the little 

 Capricorn has other tastes than its large kins- 

 man's; for three years it gnaws the outside 

 of the trunk beneath the thin covering of 

 the bark, while the other seeks a deeper 

 refuge and gnaws the inside. 



The dissimilarity is yet more marked in 

 the preparations for the nymphosis. Then 

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