14:2 THE EEPOET OF THE No. 36 



and several species of Carabids, notably, Celia far eta (1)*, Bembidiuin mutatum 

 G. - H., Bembidiuin trechiforme Lee, Platynus cupreus DeJ., Pterostichus lucu- 

 blandus (2)*. 



All attenijjt was made to determine the appetites of some of these predaeeous 

 insects. The following methods were used in determining this point. Ordinary 

 small vials were employed in which single specimens of beetles were placed. A 

 small piece of moistened blotting paper was also inserted in the vial and the whole 

 tightly corked. Eggs of the Cabbage Maggot fly, freshly-hatched larvae, and more 

 mature larvas of varying lengths were placed in the vial on the blotting paper ever 

 so often, and allowed to remain with the beetle under observation. Daily records 

 were taken over a certain length of time and the amount of material devoured noted. 

 In this way we have the maximum appetite of the beetles recorded. 



Another system was employed in which two ordinary microscopic slides were 

 laid over one another and kept separate by means of a small strip of thin linoleum 

 placed around three sides and glued on both sides to the glass. The fourth side 

 was left open to be plugged with a piece of cotton wool. In this way we have a flat 

 glass-encased chamber which may be easily handled and operated under the micro- 

 scope. A little pulverised soil was then sifted into the chamber thus formed and 

 the beetles to be observed placed within. Food was regularly supplied and the 

 amount devoured recorded. 



It may be seen from both these systems that the beetles were confined within a 

 small area and that the food supplied had no opportunity of escape. Hence due 

 latitude must be given the appetite record. Attempts were made to carry on the 

 work under more natural conditions, but it was felt that the results recorded were 

 of little value. It was too difficult to give the beetles full liberty of action 

 and at the same time keep them under observation. Furthermore, it was impossible 

 to discover whether a small newly hatched larva had been actually devoured by the 

 beetle when given full liberty of action, or whether it had died a natural death. 

 It is true that we devised a cage over some plants in the field, consisting of ordinary 

 chicken wire mesh, which was entirely covered with cheesecloth, with the exception 

 of a couple of inches on the ground surface. In this way the flies were prevented 

 from oviposting and tlie ground beetles were allowed free access to the plants, and 

 provided one knew how many eggs were around the plant at a given time, a series 

 of notes ^on this point would offer some evidence on the matter of the natural con- 

 trol. However, even this method did not give the results expected. 



I shall give, nevertheless, the results of the vial experiments, which may be 

 taken to record the maximum appetite and the length of life of the beetles. 



In this Table B the symbol " n, h, m," represents the words "newly-hatched 

 maggots," while " 1 m " represents the words " large maggots." The figures in 

 brackets in connection with these symbols represent the amount of food offered 

 throughout the course of the beetle's life. 



The species involved in this work are as follows : — 



Type 1. — Bembidium m.utatnm. 



Type 2. — Bemhidinm trechiforme. 



Typo 3. — Pterostichus luciiblandus. 



Type 4. — Orus punctatus. 



Tvpe 5. — Xantho'linus hamafus. 



Type 6. — Hisperohium calif or nicum. 



* (1) Identified by Dr. E. C. Van nyke. 



* (2) Identified by Col. T. L. Casey. 



