Stridulating Organs in Coleoptera. 489 



the so-called "death-watches" — have such a different 

 means of producing sound. 



On the hinder part of the underside of the head of 

 Priobmm castancum, Fab., a comparatively large sub- 

 circular area is to be seen, bounded at the sides by sutural 

 lines. This area is slightly convex, and is traversed 

 towards each side by a regular series of very fine, parallel 

 transverse ridges. The ridges are not continued across 

 the median part of the circular space, so that there are 

 in reality two sejiarate striated areas, each somewhat 

 elliptical in outline. 



In Dryopliilus pusUlus, Gyll, the position of the stridu- 

 lating organ is the same as in Priohium, but in this case 

 the striiB appear to run right across the whole of the 

 circumscribed space forming but a single stridulating 

 area. 



In the genus Anobiuiii proper, the gula is less extensive 

 than in Priohmm, and has no trace of a stridulating area, 

 but in many of the species there is a curious series of 

 ridges on the underside of each elytron close to its outer 

 and apical margin, suggesting that the elytra may in these 

 cases be used for purposes of stridulation. These ridges 

 are not present in Priohium, and are wanting also in 

 JCestohium tessellatum, — one of the species which are known 

 to make a noise by tapping their head against the wood 

 on which they stand. 



The stridulation of Scohjtidm was first noticed by Dr. 

 T. A. Chapman, who, in a very instructive article on the 

 habits of these insects,* relates among otlier facts, that 

 " Scolytus destructor, intricatus and 2^''U7ii squeak audibly, 

 by a rapid movement of the abdomen against the elytra, 

 intricatus making the loudest sound." 



This statement was accepted by Darwin and others, and 

 apparently has never since been disputed. For my own 

 part, being curious to examine the stridulating organs in 

 these insects, and not doubting the accuracy of so keen 

 and critical an observer as Dr. Chapman, my search was 

 for a long time confined to the elytra and abdomen, but 

 with negative results, forcing me to the conclusion that 

 Dr. Chapman's statement must have been based solely on 

 his observation of the movements of the insects and not on 

 any actual examination of the structures concerned in 

 stridulation. This was fully confirmed when later I found 

 * "Eat. Mo. Mag." VI, p. 130 (1869). 



