NATURAL CONTROL. 49 



wireworms were removed just as soon as they showed traces of the 

 disease. In spite of all these precautions the disease spread un- 

 checked until, within 10 days of its appearance, it had kiUed every 

 wire worm in the petri dishes, to the number of about 1,000. 



The disease spread in the same way every time, and the wireworms 

 kiUetl by it were so characteristically colored that they could never 

 be mistaken. When a larva became diseased, there was a very faint 

 reddish coloration in the anterior portion of its body. When placed 

 under the irdcroscope, it looked as if the head and thoracic segment 

 contained little, brilliant red, oil globules. The following day the spec- 

 imen would be a deep blood-red all over its body and so putrid that 

 when picked up on a pin point it would fall to pieces. The larvae 

 immediately surrounding it would show the faint red coloration and 

 the following day they would be red and putrid, while the larvae 

 nearest them would be showing signs of infection. When the dishes 

 were not sterilized, all the larvae in a dish would be killed in from 

 three to four days. 



That the red bacterium was the cause of the trouble was very 

 strongly suggested by the fact that whenever one infected wireworm 

 was placed in a sterile cage the disease immediately made its appear- 

 ance. This was further borne out by the fact that where a whole 

 infected wireworm was used to make a culture on agar, a pure culture 

 of the red bacterium almost invariably resulted. When the cultures 

 were made on agar, the colonies showed in their true color — a beau- 

 tiful rich blood-red. (See PI. VIII, fig. 1, p. 20.) 



It is interesting to note at this time that the mature wireworms 

 which were exposed to infection by this bacterium were never affected 

 by it. 



Everything considered, the larvae of Limonius cdlifomicus seem to 

 be affected very little by their animal enemies and by their fungous 

 and bacterial diseases, even when these latter are working under 

 favorable conditions. 



Fungi Affecting the Pup^ and Eggs. 



A few pupae in the laboratory were attacked by a fungus and pre- 

 sumably kiUed by it, as they died a short time afterward. As this 

 occurred only in two cages and as no fungus-kiUed pupae were found 

 out of doors, it is probable that this iiafection only occurs under arti- 

 ficial conditions. Even if it did occur in the fields it would spread 

 slowly, for during the time the insect is in the pupal stage the humidity 

 is low and the soil in the fields is rather dry. 



A fungus which attacked and killed some of the eggs of Limonius 

 californicus in the rearing cages in the laboratory would probably 

 seldom or never occur out of doors. Even if it did it would not be 

 6140°— Bull. 123—14 4 



