248 THE AMERICAN MONTHLY [November, 



the first and second stomachs I have rarely seen it at all. In the third 

 stomach it may occasionally appear, but there it never attacks the epi- 

 thelium. In the fluids of the body cavity, in the fatty bodies, in the 

 Malpighian tubules, in the muscles, and in the nervous masses, it is 

 totally wanting, even in the specimens w^orst diseased. Perfect slides 

 of this bacterial species ma}' be made by smearing diseased coeca on a 

 cover-glass, and staining and mounting by the usual methods. 



The effect on the insect is not remarkable, beyond a slowly increas- 

 ing lethargy, clumsiness, and weakness, usually but not always accom- 

 panied by a swelling of the abdomen and a greenish hue of the under 

 side of the body due to the tint of the fatty bodies within. In the later 

 stages chinch bugs placed upon their backs cannot right themselves, but 

 can only feebly move their legs. Death by this disease is not followed 

 by decay or by any post mortem development of fungus growths. The 

 attack is most likelv to appear in the growing insect, and in the stage 

 iiext preceding the adult, just previous to the last moult, a period of 

 extraordinary susceptibility in insects generally, but adults are often 

 seriously and even fatally affected. Although the disease is to all appear- 

 ance contagious, and occasionally destroys vast numbers of these insects 

 together, strict proof of its transmission is yet wanting. Attempts at 

 cultures made previous to the last few weeks have been only doubtfully 

 successful, owing to the evident sensitiveness of this micrococcus to cul- 

 ture conditions, and to the difficulty experienced of getting a pure infec- 

 tion material. By isolating the alimentary canal of chinch bugs by 

 dissection, and separating the coeca and transferring them entire to cul- 

 ture tubes of agar, beef broth, and the like, I have lately succeeded, in 

 conjunction with Professor Burrill. in making perfectly pure cultures 

 in considerable number in both animal and vegetable media in both 

 fluid and 'solid states. i\s a result of the infection by this method of 

 sixteen culture tubes containing, respectively, beef broth and infusions 

 of corn stalks and of potato — each medium being represented by per- 

 fectly neutral, by acid, and by alkaline tubes — we have obtained success- 

 ful cultures in all the neutral and alkaline fluids and in none of the acid 

 ones, and from these fluid cultures have made transfer cultures on solid 

 agar with entire success. 



The sensitiveness of this micrococcus to acid in its culture fluid is 

 probably the cause of its strict limitation to the coeca of the insect intes- 

 tine, since these coeca do not contain any portion of the food, but serve 

 only as a secreting gland. The secretion must be neutral or alkaline, 

 while the partly digested food is probably acid. As the excretion of the 

 Malpighian tubules is acid, the immunity of these structures has a simi- 

 lar explanation. It is a point of special entomological interest that we 

 have in this microbe a possible test of the chemical character and physio- 

 logical action of the fluid secretions of the cwca of insects — a matter yet 

 in controversy. 



Concerning the utilization of artificial cultures of the micrococcus for 

 a propagation of this disease among insects not affected, I am at present 

 able to say but little, as I have not yet succeeded, in either season when 

 it was common, in finding lots of chinch bugs sufficiently free from it 

 to make them suitable subjects for experimental attempts at its transfer. 

 It will be readily understood by any one that it is useless to test the 

 utility of artificial cultures of the disease germs by applying them to 



