LIFE HISTORY AND HABITS. 21 



When these hirvje are cxposcnl to a moderately subtku'd lioht thoy 

 color quite rapidly and become noticeably yc^llow all over their 

 bodies m a day's time. When the newly hatched larvae are kept in 

 darkness they color more slowly, and two or three days elapse before 

 their bodies become yellowish. Their skin is quite tender, but in 

 s])ite of this they can survive rather rough handling. 



REARING CAGES USED. 



Several styles of cages w(M-e used in an endeavor to find one in 

 which the wireworms could be successfully reared and at the same 

 time watched. Only three types gave any promise of success, and 

 these will be reviewed briefly. 



The first t^^pe used was simply a petri dish with damp filter paper 

 in it. Several sheets of filter paper were used so that when the 

 larvae crawled between the sheets it was almost the same as if they 

 were in damp soil. Slices of beets were placed in the cage and 

 renewed daily. These were of use not only as food for the wireworms, 

 but they also assisted in keeping the atmos])here of the dish damp 

 and cool. These dishes were then kept m insect boxes to insure per- 

 fect darkness and to assist in keeping the temperature even. This 

 style of rearing cage was very successful for the first two weeks, and 

 much was expected of it, but from that tune on one bad pomt after 

 another presented itself, and within a month the cage was given up 

 as impractical. The two worst points m connection with this cage 

 are that the amount of moisture can not be regulated and, secondly, 

 that there is no drainage and the cage teiids to foul easily. The 

 cages were cleaned every day and fresh filter paper added, but in 

 spite of all these precautions a red bacterium (PI. VIII, fig. 1) made 

 its appearance in several of the cages at about the same time, and as 

 there seemed to be no way to check it this style of cage was given up. 



Another rearing cage (fig. 5) which was used was made of plaster 

 of Paris, and was patterned after the Janet ants' nest, except that it 

 was more simple. It is a plaster-of-Paris block with two depressions 

 in it. Water is kept in one and the wireworms in the other. The 

 water readily soaks through the block, and if the dish is covered 

 with a tight-fitting piece of glass the depression containmg the wire- 

 worms is kept damp and cool. The cage is further improved by 

 pamtmg the glass plate black to exclude liglit. Dr. Chittenden sug- 

 gested a coating of paralfin for the outside of the dish to cut down 

 the excessive evaporation. This scheme worked well where only 

 part of the dish was coated. Whenever the entire outside of the cage 

 was coated, however, the drainage was cut off, the cage became foul, 

 and the wireworms died. The great advantage of this cage, as 

 pointed out by Messrs. Knab and Dimmock, is that it can be sterilized 

 simply by heating. Most of the first trials of this cage were failures. 



