26 



INTRODUCTION. 



vibrations by the air during respiration. This is found in the 

 cockchafer, and the well known boom of the dor-beetle (Geotrupes)- 

 is evidently due to it. 



The whole question of the auditory organs in insects is a very 

 obscure one. Graber (Denks. Ak. Wien, xxxvi) has discovered that 

 extirpation of tympaniform organs does not diminish the effect of 

 sounds in the ease of the Orthoptera, and this much modifies our 

 ideas with regard to the organs in this order. It is probable 

 that if a true auditory sense exists in the Coleoptera, it will prove 

 to be connected with the characteristic isolated setae which are 

 found in so many beetles, and are evidently of great importance 

 in their economy. These setae are in close connection with, 

 important nerves and are probably sensitive to vibrations (especially 

 such as would be caused by stridulating organs) as well as to 

 actual touch. It is probable that some of the strange structures 

 found in the antennae of insects may have to do with hearing as 

 well as other functions. Lubbock (Ants, Bees, and Wasps, 

 pp. 226-227) considered that certain curious organs in the 

 antennae of ants were very probably auditory organs, although he 

 has elsewhere stated that some ants, like the Orthoptera, have 

 organs of hearing on the tibiae. As, however, he failed to prove 

 by his experiments that these insects have any auditory powers, 

 the truth of this hypothesis is doubtful. 



It is quite possible that similar structures, which seem evidently 

 to be connected in some way with the senses, may be found in the- 

 Coleoptera, although none have been hitherto observed. It is not 

 impossible also that the antennal pits in Adelops, Melolontha and 

 other Lamellicornia, the Buprestid^, etc., have to do with 

 hearing or with smell, or even with a sense of which we know 

 nothing. 



The sense of touch in the order is evidently very highly developed. 

 The special setae, before referred to. are certainly most sensitive, 

 and they are so constant that specific or even generic or divisional 

 characters have been founded upon them by some authors. These 

 setae are very common in the Carabid^e, Staphylinid.e, etc., but, 

 so far as is at present known, do not occur in any Lamellicornia 

 except in the somewhat abnormal genus Aclopus, in which the 

 dorsal surface of the pronotum is quite free from hairs except for 

 one or two placed in sensory pits on each side of the middle line. 



The antennae are, evidently, to a great extent, tactile organs, 

 and the setae with which they are furnished must greatly increase 

 their sensibility, these setae being also found, to a greater or less 

 extent, on the legs and abdomen. So many beetles live in the 

 dark that they must necessarily possess such sensitive tactile 

 organs. 



Before leaving the subject of the organs of sense in the Coleo- 

 ptera it is perhaps necessary to say that the terms adopted are 

 merely provisional, and that although insects appear plainly to have 

 the organs of sight and touch well developed in a manner analogous 



