iO LUCANID^ AND PASSALID^. 



adults. When separated from the latter in an early stage 

 they invariably died. 



The (juestion of j)arental care must therefore be regarded as 

 needing further investigation. It seems certain that the young 

 larvae depend for a time, at least, upon food material ])repared 

 l)y the adults. The degree of dependence no doubt varies 

 in different species and genera. The larva differs greatly from 

 those of all other Lamellicornia and the existence side by side 

 of larvse and adults is highly exceptional and must have some 

 special significance. It occurs also in the " Ambrosia-beetles " 

 (Platypodid^ and Scolytid^) in which a social organization 

 varying in its degree of complexity has been found to exist. 



Whether or not the stridulatory power of the adults and 

 young is used as a means of inter-communication, as Ohaus 

 maintained, the possession of the faculty so highly developed 

 in both throughout the family seems to indicate a greater 

 importance than it has in any other group of beetles, for in 

 general the occurrence of these organs is rather erratic. The 

 profound structural modifications by which the stridulatory 

 organs have become perfected also show this. Owing to the 

 complete transformation of the third pair of legs of the 

 larvae into stridulating organs the creatures have acquired 

 a method of locomotion by two pairs of legs only which is 

 quite unlike that of other insect larvae. In the adults flight 

 is evidently of less importance than stridulation, for in a 

 number of different species the alteration of the wings, the 

 rubbing of certain specialized parts of which, by bosses situated 

 upon the abdomen, produces the squeaking sound, and the 

 fusion of the edges of the elytra, against which the wings are 

 pressed, has resulted in the complete loss of all power of 

 flight. As to the real use of stridulation, further investigation 

 is much to be desired. In a paper dealing with ' The Origin 

 of Stridulation in Beetles ' (Proc. R. Ent. Soc, A. 17, 1942, 

 ]). (S.3), I have suggested tlie possibility that the vibration 

 resulting fi-om the movements may serve as a protection 

 against [)redators or parasites, the sound being only incidental. 



Social instincts of an elementary kind have been found to 

 exist in at least one member of the Lucanid^, the European 

 Sinodendron cylindricum . The late Dr. T. A. Chapman 

 described (Ent." Month. Mag. vol. v, 1868, p. 139) his discovery 

 of tliis insect in tlie ])rocess of nidification. A burrow about 

 G inches long, with shorter branch-tunnels, was driven into 

 tlu> dead and lotten wood of an old ash tree by a ])air of beetles 

 working in collaboration. The excavation was begun some- 

 times by the male and sometimes by the female but soon after 

 a pair were found at work together, the female extending 

 the burrow while the male a])peared to employ himself by 

 removing the excavated material. Wideiiings of the burrow 



