LAKVAL HABITS OF THE TIGER BEETLES. 177 



The effect o£ cold on the development of colour is similar : lowering the 

 temperature ten degrees in C. Umhalis caused an increase o£ time for develop- 

 ment to three or four times and in some stages of the development it stopped 

 it altogether. Such influences of temperature on growth, respiration, &c., 

 have been noted hj various workers. 



C. Moisture Relations. 



As will be noted in Table IV., purpurea Umhalis does not respond strikingly 

 in the depth of its burrows to moisture conditions. The relations of the 

 depth of burrows to the soil moisture in nature has been found not to be 

 striking. The larvse that have burrows near the ground water-level never go 

 to a depth which would give actual water in their burrows, and accordingly 

 may have shallow burrows. When above the ground water-level variations 

 in depth are apparently not definitely related to soil moisture. Statistics on 

 this point are very contradictory. 



With the exception of the larvse of C. duodecimgtittata, its subspecies repanda, 

 and Jiirticollis, the species described in this paper do not leave the spot where 

 the female lays the eggs, except under very unusual circumstances, such 

 as the complete flooding of the habitat. Only a small percentage of the 

 individuals come out even under such conditions. When too dry, they close 

 the burrow near the mouth and go to the bottom ; here they remain inactive, 

 and if bad conditions continue, finally die. 



When placed in sand (clay being their natural habitat) and kept at a 

 temperature of about 19° to 24° C, about 15 per cent, of the larvse of 

 C. purpurea Umhalis will leave their holes. Probably not more than from 3 to 

 10 per cent, of the larvee of the other species, with similar habitats, migrate 

 even under the very artificial conditions of my experiments. 



C. duodecimguttata, repanda, and hirticollis, on the contrary, leave their 

 burrows often. If the soil becomes too dry, they come out and seek a place 

 which is suitably moist. In ' captivity, when kept in separate receptacles 

 whence they cannot escape, they leave the soil, if it is allowed to become too 

 dry, and run around and around the side of the dish until they die from 

 exposure and exhaustion. They cannot dig a new burrow in sand if the 

 surface is dry. 



These two species thus adjust themselves to conditions and are much less 

 variable in many of their characters than other species. This is especially 

 noticeable in the geographical variation. However, since the larva? of 

 C. hirticollis have been found in unusual positions such as the tops of sand 

 dunes, after heavy rains, it is possible for them to be overtaken by dry conditions 

 after they have become helpless in connection with pupation. 



In moist conditions most of the species go through their transformations 

 two or three days to a week sooner than in very dry conditions. 



