1917] Studies on Hydromyza Confluens Loew 43 



light seems also to be overcome by the attraction to food since 

 large numbers of the flies have been found on numerous occa- 

 sions crowded into but slightly opened flowers of the yellow 

 water-lily, the interiors of which were dark. 



Distribution. — Attention has already been called (Welch, 

 '14, p. 140) to the peculiar local distribution which was so 

 marked in the Douglas Lake region. The observations of two 

 additional seasons show that such a distribution is practically 

 the same from year to year. Observations in other localities 

 where H. confluens occurs would be of interest in this connection. 



Thus far, H. confluens seems to have been reported only from 

 Canada, Michigan, and New Jersey. However, there is reason 

 to believe that it is more widely distributed than these meager 

 data would indicate. While making a very hasty examination 

 (June 27, 1915) of the life of the protected bays of Cedar Point, 

 near Sandusky, Ohio, the writer found this fly, in the adult 

 stage, in some abundance on the leaves and in the flowers of the 

 yellow water-lily. None of the immature stages were found but 

 this failure was due, no doubt, to the very superficial examina- 

 tion, lack of time preventing a thorough survey of the situation. 

 Both sexes were present and several pairs were observed in 

 copulation. Individuals collected at that time were bearing 

 the pollen of the yellow water-lily and a few specimens almost 

 completely covered with pollen were taken from the flowers. 

 Evidently they were playing an active part in the cross pollina- 

 tion of these plants. Fulton ('11, p. 300) states that he found a 

 number of flies visiting the yellow water-lilies, '' Nymphcea 

 advena," about Cedar Point but the particular species are not 

 designated and his paper contains only a list of the Stratiomyidae. 

 Bembower ('11) studied the insect-pollinated plants of the 

 Cedar Point region and while it was found that Diptera were 

 collected in connection with N. advena, the different species are 

 not indicated. 



SUMMARY 



1. Further studies on Hydromyza confluens in the vicinity of 

 Douglas Lake, Michigan, confirm observations previously 

 reported and yield new data on life history and behavior. 



2. Eggs are deposited singly and irregularly along the sub- 

 merged petioles of the floating leaves of the yellow water-lily 

 {Nymphcea americana). Oviposition apparently does not occur 

 on other plants. 



