April, '19] McCOLLOCH: ELEODES OPACA 191 



tricostata (McColloch, 1918, pp. 221-222). A gregarine (Stylocephalus 

 giganteus Ellis) has frequently been found in the alimentary tract of 

 the adults. 



Swenk (1909, pp. 335-336) encountered considerable difficulty in his 

 rearing work, due to the presence of what was apparently a bacterial 

 disease. This disease usually began as a small dark red spot on the 

 thoracic segments, or on the terminal abdominal segments, and spread 

 rapidly, soon encircling the body, resulting in the death of the larva. 

 Where several larvae were confined in the same cage, the disease often 

 spread to the others. The writer has often encountered this same dis- 

 ease, but since the larvae were reared in separate boxes, it never spread 

 to any extent. Two species of fungi have been found attacking the 

 larvae, namely, Sporotrichimi glohidiferum and Metarrhizium sp. 



Physiological Relations 



Eleodes opaca is a typical species of the Great Plains, an area of low 

 rainfall and rather high temperatures. While it has been recorded as 

 far east as Iowa, it does not occur in large numbers east of the 98th 

 meridian. It is not common to the vicinity of Manhattan, being found 

 only on the high, grassy uplands. The years of greatest injury in west- 

 ern Kansas have been characterized by excessive temperatures and 

 low rainfall. In the. life-history studies, eggs, kept in cages where the 

 maximum temperature during the day was 112°, and the relative 

 humidity 25 per cent, hatched in six days. The adults were not 

 affected by a daily temperature of from 105° to 112° when the humidity 

 was low. In ovipositing, the adults showed a preference for dry soil, 

 and the rate of egg-laying decreased when the beetles were placed in 

 cages containing moist dirt. Some moisture, however, is required by 

 the adults, and this was supplied by feeding wet bran once a week. 

 The larvae thrived best in a slightly moist soil. When the soil was too 

 wet to crumble nicely, the mortality increased rapidly. High tempera- 

 tures, such as experienced by the eggs and adults, were fatal to the 

 larvae and the best results were had by keeping them in a cave where 

 the temperature remained constant at about 80° during the summer, 

 falling slowly to 39° in midwinter. There is some evidence that the 

 larvae can withstand low temperatures, and Swenk (1909, p. 334) cites 

 a case where they survived a twelve-hour exposure to a sweeping wind 

 of from 59 to 72 miles an hour velocity, with the temperature about 

 zero. 



Like most of the species of the genus, the adults of opaca are nega- 

 tively phototropic to strong light. During the day they are usually 

 to be found hiding under various types of shelter, confining most of 

 their activities to the early morning, evening, and night. Tlic larvae 



