60 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



Deposition 



The determination of the egg-laying period of a fly or group of flies 

 is important in that it shows the value of destroying the adult at differ- 

 ent times in its career as relates to reproduction. In most of our tests 

 the total time from the beginning of laying to the deposition of the last 

 eggs was comparatively short, the adults often living several days after 

 the last eggs were deposited. 



Dr. A. Griffith, reporting on experiments conducted by him in Eng- 

 land, says: ''After ten days the mother-fly can lay a new batch of 

 eggs, which process it repeats at intervals of ten to fourteen days, till 

 four batches have been layed, when it dies."^ Our observations indi- 

 cate that in Texas fewer batches of eggs, the usual number being two, 

 are deposited and that depositions take place at shorter intervals — 

 about eight days. 



Oviposition was observed to occur on warm days in mid-winter at 

 Dallas (January 14) and Uvalde (February 5). Depositions may be 

 expected at these latitudes on mild bright days in winter, especially 

 if these are preceded by a few days of mild weather. 



During cool weather adults seem to choose places for deposition 

 where the sun is bright and the wind is cut off. They also prefer 

 portions of the pile where heat is emanating from beneath, provided 

 the media is suitable. In summer this is less noticeable though in 

 mornings and evenings sunny places seem preferred. 



We have observed a marked tendency to clustering of eggs in one 

 place on manure piles. In many instances from three to over a dozen 

 flies have been observed depositing in one spot in a manure pile and 

 scarcely a depositing fly or an egg could be found elsewhere, although 

 equally favorable places seemed to exist. This habit of association of 

 individuals seems to continue to some- extent in the larval stage, al- 

 though this is probably more dependent on suitable feeding places, 

 and the fact that the Islyvs^ hatch largely in one mass. Great masses 

 of larvae have also been observed to pupate in one place. This is 

 probably due, in part at least, to many of the larvae following the line 

 of least resistance in migrating and the finding of a place which fur- 

 nishes proper protection and moisture and is not too compact. 



Developmental Periods 



Incidental to other observations the developmental periods were 

 determined in a large series of tests at different times of year. The 

 total period from the deposition of the eggs to the emergence of adults 



1 1908. Griffith, A. The life history of house flies. Public Health, Vol. XXI, p. 

 123. 



