might easily survive passage through the intestinal canal 

 of the insect. Graham-Smith (1909) examined ikS flies 

 caught in various parts of London and Cambridge, and 35 

 (2U$>) possessed externally or internally, or "both, hacteria 

 "belonging to the colon group. Later (1913); he reported 

 that Serratia marcescens could "be cultivated from the con- 

 tents of the crop and intestine of the housefly in large 

 numbers up to k or 5 days after inoculation and survived 

 in the intestine up to 18 days. Graham-Smith also states 

 that although it seems to have "been proven that the spores 

 of Bacillus anthracis may survive after "being ingested "by 

 fly larvae, most observers agree that such non-spore- 

 forming pathogenic organisms as Eberthella tvphosa, 

 Salmonella enteritidis , and Shigella dys enter iae derived 

 from cultures and added to the food of the larvae are not 

 present in the flies which emerge, except under very 

 special and highly artificial conditions. However, as 

 stated elsewhere, Bacot (1911) reported that when the 

 food of newly hatched larvae of Musca domestica was 

 inoculated with a culture of Pseudomonas aeruginosa , 

 viable "bacteria remained in the gut during metamorphosis. 



Torrey (1912) observed that flies examined up to the 

 latter part of June were free from fecal "bacteria of 

 human origin and carried a homogeneous flora of coccal 

 forms. During July and August, periods occurred when 

 the flies examined possessed several millions of "bacteria, 

 alternating with periods in which the number of "bacteria 

 was reduced to hundreds. Bacteria of the colon type was 

 first encountered in abundance during the early part of 

 July. Another example of seasonal incidence has "been 

 observed in the case of the "bacteria producing soft rot 

 of potatoes. In this case the "bacteria pass the winter 

 in the digestive tract of the puparia of Hylemyia cili - 

 crura (Leach, 1933). Nicoll (1911), and Cox, Lewis, and 

 Blynn (1912) also studied .the numbers and varieties of 

 "bacteria associated with the housefly, finding large 

 numbers of the coliform type. (See also Hewitt, 191^)* 



Cecal Bacteria . In certain insects of the order 

 Hemiptera peculiar sac -like appendages are found opening 

 into the posterior end of the mid-intestine. These 

 structures, called ceca or bacterial crypts, are of var- 

 ious shapes and sizes and always harbor enormous numbers 

 of bacteria morphologically characteristic for the par- 

 ticular species of insect harboring them. 

 > 



This bacteriologic-entomologic relationship was first 

 studied in 1888 "by Forbes (1892) during his investigations 



