278 ENTOMOLOGICAL NEWS. [June, '17 



Plate XX. 



Fig. I. Two eggs of Notonecta undulata after hatching, showing the 

 characteristic sHt in the shell and the clear embryonic mem- 

 brane shed by the nymph upon emerging. 



Fig. 2. Adult Xotonecta undulata in the water. 



Fig. 3. Egg nearly ready to hatch — note the red eye spot and the dark 

 line at margin of the gelatinous substance which glues the 

 egg to its support. 



Fig. 4. A freshly laid egg viewed from above. 



Fig. 5. A roadside pool in early spring. The backswimmers were 

 arriving in numbers flying from some unknown quarters 

 where they had passed the winter. 



Fig. 6. Eggs of Notonecta undulata freshly laid upon old weed stems 

 lodged in the waters of the pool. Gyrinid beetles lay some- 

 what similar eggs which may be distinguished by their ar- 

 rangement upon their support and by the fact that the eye 

 spots in advanced eggs are black instead of red and farther 

 from the end of the egg than in those of the backswimmers. 



Seasonal Abundance of Flies in Montana (Dipt.).^ 

 By R. R. Parker, Bozeman, Montana. 



During the season of 191 4 the Montana State Board of 

 Entomolog}' started investigations to determine the life histor}' 

 and habits of the house fly (Musca domestica Linnaeus) and 

 flies of similar habits common in Montana cities and towns 

 and their relation to insanitary conditions. Investigations dur- 

 ing 19 14 were conducted mainly at Laurel and incidental ob- 

 servations were made at other points in the Yellowstone Val- 

 ley during the same season. In 191 5 the work was carried on 

 at Miles City and the more important results have been pre- 

 sented in the Journal of Economic Entomology for June, 1916 

 (pp. 326-354). Observations incidental to other work have 

 been made in various other localities. 



The present paper concerns the seasonal abundance of flies, 

 particularly the house fly, and the most important portion is 

 based on work done at Laurel during July and August of 1914. 

 This town had a population of about 1200, the houses were 



^Contribution from the Laboratory of the Montana State Board 

 of Entomolog>% State College, Bozeman, Alontana. 



