120 HUGH GLASGOW. 



In the squash bug the caecal bacillus is a very short, uniform 

 rod, averaging 0.9 micron long by 0.7 micron wide. As they 

 occur in the caeca these bacteria do not show the slightest indica- 

 tion of motility ; and they are usually arranged in pairs, or they 

 may, exceptionally, form short chains of from three to four or 

 more individuals. 



In undertaking the culture work with this insect I had very 

 little hope of growing the caecal bacteria successfully, and really 

 did not expect more than a repetition of the negative results 

 secured with the Pentatomidae, but I nevertheless thought that 

 even the relation shown there would be worth establishing in 

 other Heteroptera. 



The first culture experiments with Anasa tristis were under- 

 taken with seven adults that had been kept in a warm room for 

 nearly a month. Of the tubes inoculated from the caeca of 

 these seven insects, every one developed growth; and in each 

 case this appeared to be a pure culture of an organism morpho- 

 logically very similar to the bacteria in the caeca; but as these 

 insects had been feeding on partly decomposed squash a short 

 time before the dissections were made, it was realized that the 

 growth might very easily have been due to some foreign organism 

 swallowed by the insects while feeding. Nevertheless, the fact 

 that the growth in all the tubes was apparently the same, was 

 very encouraging in view of the uniform failure to secure any 

 growth whatever from the Pentatomidae. 



To ascertain whether or not this growth was merely a con- 

 tamination from the squash, or whether the caecal organism could 

 still develop saprophytically, as the cultures suggested, a series 

 of fifty specimens of Anasa were taken, fed on perfectly fresh 

 squash for two weeks and then kept for a full week without food, 

 in order to give the caecal bacteria sufficient time to destroy any 

 contaminating organisms that might have been swallowed while 

 feeding. 



Cultures were made from this series and, to my surprise, 

 growth developed in all fifty of the tubes and appeared in each 

 case to be a pure culture of a short, motile organism identical 

 in size and form with the bacteria in the caeca of this insect, 

 and so far as could be determined these were the same as the 



