260 Illinois State Lahoratorij of Natural History. 



Advancement of Science at its Minneapolis meeting in August, 

 1883, and of this a synopsis appeared in the " Canadian Ento- 

 mologist" for September, 1883. In the "Prairie Farmer" 

 (Chicago) for October 6. 1883, and in "Science," also, for 

 October 5, 1883, brief notes occur with reference to this dis- 

 ease in the cabbage worm. 



In the Transactions of the Illinois State Horticultural So- 

 ciety for 1883 (printed February, 1884) is a somewhat elab- 

 orate paper on the Contagious Diseases of Caterpillars, read 

 before this Society December 18, 1883, giving a general and 

 rather popular account of the character of the work done by me 

 on this subject, up to that time ; and a still more elabo- 

 rate paper (never published) was read before the State Nat- 

 ural History Society of Illinois, at its meeting in Peoria, July 

 8, 1884, in which a classification of insect diseases was pre- 

 sented, and a full resume of methods and results, up to that 

 date, was given. At a meeting of the State Horticultural So- 

 ciety, held at Champaign, December, 1884, I added some fur- 

 ther items relating to cultures and experiments, especially those 

 affecting the cabbage worm, and these notes were published in 

 April, 1885, in the Transactions for the year preceding. 



It is my purpose, in this paper, to present the principal 

 results of the above studies, — both the successful and the un- 

 sucessf ul issues, — the latter so far as they have any significance 

 or value. 



Disregarding the chronological order of my observations, I 

 shall first discuss jiacherie of the cabbage worm, and jaundice 

 of the silkworm, with experiments upon the former insect with 

 the artificial cultures derived from the latter. I will then take 

 up the longer and more complicated record of Jiacherie in our 

 Datana larvae and the experiments drawn from it, and will con- 

 clude with a brief account of the muscardine of the forest tent- 

 caterpillar. 



EUROPEAN CABBAGE WORM (Pieris rapce, L.) 



In studying experimentally an insect disease, it is necessary, 

 in the present state of our knowledge, (1) to determine pre- 

 cisely the symptoms and character of the disease itself, in order 

 that it may be subsequently recognized with certainty; (2) to 



