85 

 THE DEVELOPMENT OF THE MEDITERRANEAN FLOUR MOTH. 



By F. H. Chittenden, Washington, 1*. C. 



In the article on insects injurious to stored grain prepared by the 

 writer for the Yearbook of the United States Department of Agricul- 

 ture for 1894, the following statement was made on page 285 concerning 

 the development of the Mediterranean flour moth (Ephestia Imehniella 

 Zell. ) : " From experiments conducted during the year at Washington it 

 is estimated that under the most favorable conditions, i. e., in the 

 warmest weather, the life cycle consumes about five weeks." This 

 estimate was given in comparison with the record of M.J. Danysz who 

 conducted observations on the development of this species in France. 

 M. Danysz gives on page 11 of his memoir on this moth* a brief state- 

 ment showing that from moths that issued under his observation from 

 the 15th to the 20th of August a second generation of moths developed 

 from the 13th to the 18th of October. He concludes with the state- 

 ment: "Thus we have obtained a complete evolution in about two 

 months, from the 15th of August to the 15th of October." 



My estimate of five weeks is quoted by Mr. W. G. Johnson in his 

 excellent article on this species recently published as an appendix to 

 the Nineteenth Eeport of the State Entomologist of Illinois (p. 28) in 

 contrast to experiments conducted by that writer " during midsum- 

 mer, under the most favorable conditions in California and Illinois," 

 whereby he was unable to obtain a full- grown larva in less than five 

 weeks from its emergence from the egg, his shortest period from the 

 deposition of the egg to the issuance of the adult being placed at fifty- 

 nine and one-half days. 



This experiment, according to Mr. Johnson's table on page 29, was, 

 I judge, conducted at Champaign, 111., from April 29 to June 28, 1895. 



My estimate has gone on record without the details to substantiate 

 it, the limited space allotted me for my Yearbook article having been 

 insufficient for the purpose. 



With a view to the ascertainment of the exact truth, a series of 

 experiments was undertaken the present year as soon as the weather 

 promised anything favorable in the way of obtaining minimum devel- 

 opmental periods. 



In my experiments to determine the life history of insects affecting 

 stored products a special effort has been made to determine the mini- 

 mum period of each stage. The reasons are these: With but few 

 exceptions, indoor insects are of tropical origin and attain their highest 

 development and are consequently most troublesome in warm climates. 

 Again, with scarcely an exception, the different species cause, by their 

 ravages in cereals and other products, a certain amount of decomposi- 



*Memoires du Laboratoire de Parasitologic vegrtale de la- Bourse de Commerce, 

 Vol. I, 1893. 



