LIFE HISTORY AND HABITS. 39 



EFFECT OF TEMPERATURE ON THE ADULTS. 



The adults of many of the eastern species have been reported by 

 some observers as bemg prmiarily nocturnal in habits.^ Other 

 observers record them as flying readily both by day and night. The 

 adults of Limonius califomicus seem without exception to be warm- 

 weather insects. They not only attain their greatest activity 

 during the middle of the day when the heat and light are at the 

 maximum, but during the morning and evening hours they are 

 sluggish and quiet. Some specimens were kept in the winter's 

 room durmg their entire life and none was ever observed feeding or 

 copulating at night . On the warmest nights a very few were observed 

 moving about sluggishly, but their activity at this time can not be 

 compared to that which occurred during the daytune and especially 

 when the temperature was over 75° F. 



Several experiments were conducted for determining the direct 

 relation between temperature and activity. The apparatus used 

 was very similar to that used in the boll weevil investigations,^ 

 except that instead of the outer tube a flask was used, as it was believed 

 that this would afford more even heating. 



The results agreed quite closely with those recorded in Bulletin 

 No. 51 (pp. 101-102) and an approximation is given below: 



48° F. Beetles quiescent. 



54° F. Few crawling about sluggishly. 



60° F. Beetles all moving about. 



70° F. Beetles becoming active. 



75° F. More active, few flying. 



80° F. Many flying. 



85°-90° F. All flying, very active, seem greatly excited. 



93°-94° F. Period of greatest activity. 



97° F. Few becoming quieter. Seem to be suffering. 



99° F. Many becoming quieter. 



This experiment was varied slightly by placing damp filter paper 

 in the inner tube so that the heat would not be so dry. The new 

 results did not differ very starthngly from the preceding, except 

 that the beetles did not seem to suffer so much at the higher tempera- 

 ture and seemed less excited. 



Under field conditions 75° to 80° F. seems to be the optimum 

 temperature for their various activities. At 70° F. they are ciuite 

 active, but few are noted in flight, especially if there is a moderate 

 wdnd blowing. At 60° F. very few are noted moving in the fields, 

 and these are generally close around the beets under which they have 

 been hiding. The beetles are always more active on bright days 

 than on darker days, even if the temperature is the same. This 



1 Comstock and Slingerland, Bui. 33, Cornell Agr. Exp. Sta., 1891. 

 a Bui. 51, Bur. Ent., U. S. Dept. Agr., PI. XVI, fig. 72, 1905. 



