258 Illinois State Lahoratory of Natural History. 



State Entomologist of Illinois (pp. 45-57). This article con- 

 tained an account of a considerable series of microscopic obser- 

 vations on the fluids of chinch bugs apparently affected with 

 disease, and described some successful attempts at the culture of 

 the Micrococcus found invariably characterizing this insect 

 affection. Time failed for further experiments, and the chinch 

 bug has since been so scarce in my vicinity that no further op- 

 portunity has offered to complete the study of the subject. The 

 observations made amounted to a practical demonstration of the 

 occurrence of a " germ disease " in this insect species, iden- 

 tified ^he germ as a Micrococcus, since described as Micrococcus 

 insectortim, Burrill, and proved that this was easily and freely 

 cultivable in beef broth. The Micrococcus was shown to have 

 its seat in the alimentary canal of the insects, occurring most 

 abundantly in the posterior part of the same, to infest pupee and 

 adults more seriously than the younger stages, and to have the 

 apparent effect to retard the development of the brood as well 

 as to destroy a large percentage of them before they reached 

 maturity. This disease was apparently the representative of 

 flacherie or schlqffsucht in caterpillars, as described by previous 

 authors and in the following pages. 



Next there appeared early in August, 1883, in our breeding 

 cages of Datana ministra (the yellow-necked apple caterpillar), 

 an outbreak of disease characterized by the occurrence, at first 

 in the alimentary canal and later in the blood, of immense num- 

 bers of micrococci of a form very different from the above, 

 and evidently quite readily conveyed from one insect to another. 

 Elaborate studies of this disease were made during the remain- 

 der of the season and the following spring, the bacteria associ- 

 ated with it were repeatedly cultivated with success in animal 

 infusions, and several experiments were made to convey the dis- 

 ease by their means to still healthy larvae. Tubes of the cul- 

 ture fluids were sealed up for preservation over winter, their 

 contents were cultivated again in June, 1884, and the resulting 

 cultures were used to infect the food of larvae of Mamestra 

 picta^ with the hope of thus reproducing the original disease of 

 the Datana larvae of the preceding year. 



Parallel with these experiments was a similar series made on 

 a frightfully contagious and destructive disease of the European 



