for carrying pollen, have relatively few "bacteria on 

 their external surface. White (1906) found only three 

 species ( Bacillus A, Bacterium cyaneus , and Micrococcus C) 

 on adult "bees from normal apiaries. 



Bacterial flora of alimentary tract proper . There is 

 extreme variation in the size and structure of the ali- 

 mentary tract of the different species of insects. In 

 some species it is merely a tube extending from one end 

 of the "body to the other. In other species it is a highly 

 complex structure with various pouches, ceca, and diver- 

 ticula. In most insects the tract is longer than the 

 hody and possesses three chief divisions: the fore-intes- 

 tine, the mid- intestine, and the hind- intestine. The 

 fere- and hind-intestine are invaginations of the "body 

 wall and their chitinous lining is continuous with the 

 "body wall cuticula. The mid- intestine develops from an 

 entodermal tube, the mesenteron. 



Although very little comparative work has "been done on 

 the "bacterial flora of main divisions of the digestive 

 tract of insects, Steinhaus (19^-1) reported that the 

 milkweed "bug, Oncopeltus fasciatus Say, has a different 

 flora in its pylorum and rectum from that in the four 

 stomachs which precede them. The predominant "bacterium 

 found in the pylorum and rectum was named Proteus recti - 

 colens, while in the four stomachs the flora consisted 

 mainly of Proteus insecticolens . Eberthella insecticola 

 and occasionally Streptococcus faecalis were found 

 throughout the entire tract. 



The "bacterial flora of the digestive tract may vary 

 quantitatively as well as qualitatively. While the 

 tracts of some insects are packed with organisms others 

 have "been found to "be sterile. In the honey "bee, Hertig 

 (1923) found the greater number of "bacteria in the hind- 

 intestine, particularly the rectum, while very few "both 

 in numbers and variety were found in the ventriculus, 

 except at times of food accumulation. Occasionally, when 

 small sections of the wall and contents were inoculated 

 into media, no growth at all resulted. Hertig explains 

 the low "bacterial content of the ventriculus as perhaps 

 due to the fact that solid particles pass rapidly to the 

 hind-intestine, and also to the fact that the contents of 

 the ventriculus are at times rather acid. This might 

 inhibit the multiplication of the "bacteria. In the 

 larvae of the olive fly, Dacus oleae, large numbers of 

 "bacteria are found in the mid- intestine, few in the hind- 



