6s 2 MICROBIAL DISEASES OF INSECTS 



Causal Organism. — This bacillus is 1.2/* to 1.8/* long and from 0.6/i to o.g;* in di- 

 ameter; often in pairs; long filaments not formed. Spores are characteristically dip- 

 lospores although isolated ones occur not infrequently. It shrinks very little when 

 stained by Gram's method. 



Gelatin is liquefied; subsurface colonies are decidedly lemon shaped, yellowish 

 brown, finely granular, surface of colony typically curled. Surface colonies are con- 

 centrically three-ringed, the interior opaque, the second ring more transparent, the 

 third very thin and finely granular. Saccate liquefaction in gelatin stab; the gelatin 

 is blackened and has a very disagreeable odor. Spores are found in the sediment at 

 the bottom of the tube. Broth is made turbid in eighteen to twenty hours, no 

 pellicle, bad odor. 



Methods of Infection. — Healthy larvae inoculated with .B., se/>- 

 ticiis insectorum by placing cotton saturated with a broth, culture on a 

 wound, died in most cases with typical symptoms. 



The sole habitat of these microbes before death is in the blood 

 system. 



Bacterial Disease of the Gut-epithelium of Arenicola 

 ecaudata, the Lug- Worm 



Bacterium arenicola. — Fantham and Porter.* 



History and Distribution. — This bacillus was found in the lumen 

 of the gut and within the intestinal epithehum of specimens of Areni- 

 cola ecaudata obtained from Plymouth, England. This disease is not of 

 frequent occurrence. 



Symptoms. — No external symptoms are noted. Lesions are pro- 

 duced in the epithelium, the cells undergoing degeneration, perhaps 

 shortening the life of the lug-worm. Bad. arenicolce seems to be con- 

 fined chiefly to the ciliated tracts, as was determined by microscopical 

 examination of sections. 



Methods of Infection. — No methods of infection are noted. 

 From the type of the disease, however, infection per as is suggested. 



Causal Okganism. — Bacterium arenicplm* averages about iiju long and in 

 broad. Extreme individu,als measure 7/4 to 17/t long by o.7ju to 1.3/x broad; some of 

 the larger forms are slightly sinuous in outline; no flagella; chromatophile granules 

 determined by staining with iron-hemat03cylin, are present, often in considerable 

 numbers, scattered through the cell; these granules are often concentrated into 

 transverse bars both of which in some specimens are refractile. The cytoplasra 

 stains with difficulty with plasma stains. Division is transverse. One terminal 



* Fantham, F. B. and Porter, A. Bacillus arenicolee, n. sp., a pathogenic bacterium from the 

 gut-epithelium of Arenicola tcaudala. Cent. f. Bakt. I., Orig. 52, 1909, 329-334. 



