THE OLFACTORY SENSE OF COLEOPTERA. 4O9 



ing the specimens with caustic potash and to bleaching them 

 with chlorine gas, the reader is referred to the writer's work on 

 Hymenoptera ('14&, p. 295). 



To obtain material for the study of the internal anatomy of 

 the organs herein discussed, beetles just emerging from the last 

 pupal stage were mostly used. At this stage the chitin is soft, 

 the wings are usually expanded, and the sense organs are fully 

 developed. In order that the desired stages of beetles might be 

 had, many larvae and pupa^ of various Coleoptera were collected 

 on plants and in rotten stumps and logs. These immature 

 insects were reared in the laboratory. When each one of them 

 had reached the proper stage, it was killed and parts of it were 

 put into a fixing fluid. 



The writer ('14a, p. 268) describes the usual method of em- 

 bedding with celloidin and parafhn. Since then, a rapid method 

 has been used which is described in detail as follows: The various 

 appendages of the insects are removed, and are cut into small 

 pieces, which are immediately dropped into a modification of 

 Carnoy's fixing fluid. This fluid, containing equal parts of 

 absolute alcohol, chloroform, and glacial acetic acid, with corro- 

 sive sublimate to excess, should be kept in a glass-stoppered 

 bottle so that it may not lose its fixing ability by air being mixed 

 with it. Also, while dropping material into vials containing this 

 fluid, the stoppers of the vials, should not be removed longer than 

 absolutely necessary. When the material sinks to the bottom of 

 the vial, it is removed and is thoroughly washed in 85 per cent, 

 alcohol. It is then preserved in 85 per cent, alcohol. When 

 ready for embedding, the material is cut into pieces from two to 

 four millimeters in length. These pieces are then put into 95 per 

 cent, alcohol containing eosin. When sufficiently stained, they 

 are placed in a vial containing absolute alcohol and cedar oil. 

 As soon as they sink through the alcohol into the oil and lie on 

 the bottom of the vial, the alcohol and oil are removed. A small 

 amount of ether is then poured into the vial. Five minutes later 

 the ether is removed, and thin celloidin is poured into the vial. 

 Ten minutes still later the thin celloidin is exchanged for thick 

 celloidin. After remaining in the thick celloidin five minutes, 

 the pieces of material are removed and are put into a vial of 



