June, '16] CORY: PEGOMYIA HYOSCYAMI PAXZ 373 



limits of a single polyphagous species. The fact that he was unable 

 to get adults bred from belladonna to oviposit on mangold leaves and 

 vice versa has led him to question the statement that insects often 

 oviposit on a number of related plants. His experiments, showing a 

 preferential selection of food plants, lead him to the belief that slight 

 variations, such as in color, may arise from the adoption of preferences. 



Flies bred from Chenopodiacese {Spinacia oleracea and Chenopodium 

 album) and from Amarantacese (Ajnarantus retroflexus) do not show 

 any differences in color that would warrant the separation of varieties, 

 out of the series at hand. 



The entire series bred by Mr. A. B. Gahan and the writer from 

 the above named host plants has been carefully gone over bj^ Mr. 

 Knab. The specimens in the U. S. National ^Museum and two speci- 

 mens from Wooster, Ohio, in the possession of Mr. Gahan, all labelled 

 P. vicina Lint., have been compared with this series. Without doubt 

 they are all the same species, P. hyoscyami Panz. 



Seasonal History 



The first record of eggs found is May 15, 1915. These eggs were 

 on Chenopodium album. Three masses of 3, 4, and 4 eggs, respectively, 

 were found. 



Nearly full grown larvse were found on May 17, 1912, in spinach 

 leaves. These produced adults on June 5, 6, 7, 12, 15 and 19. 



From ^lay 15 to the first week in August the miners are readily 

 found in lamb's-quarters. After that time thej^ disappeared until 

 September when a new brood appeared. 



Repeated efforts to get the adults to breed in confinement have 

 failed and so no definite records were obtainable on the number of 

 broods. The straggling emergence of adults indicates a considerable 

 overlapping of broods. However, there are certainlj' three broods 

 during the season with a probability of the existence of at least one 

 more brood. 



The Egg 



The egg is .72 mm. x .26 mm., nearly cylindrical, white and heavily 

 reticulated. They are deposited in, rather regular rows on the under 

 surface of the leaves. The greatest number observed on a single 

 leaf was eight. Generally three or four is the usual number. The 

 time from the deposition of. the egg to its hatching approximately is 

 four days. 



The Larva 



The larva is nearly cylindrical in cross section. It tapers to the 

 anterior end when stretched out, but in life the tapering is only slightly 



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