316 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



temperature until they became frantic in their efforts to escape. The 

 high temperature speedily caused death. A lowering of the tempera- 

 ture previous to attaining the fatal degree generally brought about 

 almost normal actions though, in some cases, a period of inactivity 

 resulted before normal activities were resumed. This period of par- 

 tial inactivity sometimes lasted several days before all of the functions 

 were performed in an entirely natural way. In many cases, especially 

 when a dry atmosphere at 47° C to 48° C. was used, the insects sur- 

 viving the test would die several hours to several days later. In mak- 

 ing a large number of tests it was observed that very often the different 

 stages of the same species, succumbed at slightly different tempera- 

 tures. In every case, as far as these experiments extended, the egg 

 stage was the first to be destroyed. The resistance of the stages varied 

 with the insect, but in general that stage which endured the greatest 

 heat, or sometimes survived, was usually the dormant one in which 

 the insect passes the winter. In those cases where all stages occur at 

 all seasons, little difference in resistance could be discerned, but in the 

 case of T. ornatum, the jjartially grown, or young larva, readily sur- 

 vived a temperature which proved fatal to the other stages. 



Silvanus surinamensis was not much more susceptible to moist than 

 dry heat. In a large series of experiments the fatal temperatures 

 with moist and dry heat were not more than 1° C. apart, and the aver- 

 age was a little less than .41 of a degree Centigrade. The egg stage 

 was killed in every case by 44° C. to 45° C; 44° C. being the average 

 temperature which destroyed life in the egg. Larvae, pupse and 

 adults died at 46° C. to 48° C, the pupse proving more susceptible to 

 heat than larvae or adults. The beetles withstood treatment longer, 

 and also a slightly higher temperature. This beetle is almost a uni- 

 versal feeder, being able to live and reproduce in wheat, flour, corn 

 meal, breakfast foods, crackers, currants, raisins, dried fruits and nuts 

 of several kinds, if the shells are broken. With the exception of 

 Tribolium conjusum, it is probably the most common and destructive 

 pest affecting cereal products and ground cereals. It is not partial to 

 the end or corner of a package of cereal, as are some other species, 

 but works through the entire mass, nibbling here and there and render- 

 ing all of it unfit for food. 



Cathartus advena lives almost entirely on ground cereals, but may 

 often be found in stored grain in company with other species of Cucu- 

 jidoe. It rarely occurs in great numbers, but it is one of the common 

 stored-grain pests. A moist, heated atmosphere kills this beetle at 

 almost 1° C. lower temperature than when it is subjected to dry heat. 

 Like S. surinamensis, it does not always recover from the effects of 

 being subjected to a dry, heated atmosphere, often dying several hours 



