644 townsend: new generic name for screw-worm fly 



hours is to be preferred as the fixed position. In this position 

 the plane of vibration of the rays emerging from the polarizer 

 is parallel with the vertical cross-hair of the eyepiece. 



An extended series of tests by the writer with the petrographic 

 microscope corroborates these statements in detail, the general 

 conclusion being that, although either position of the polarizer 

 is permissible, there is a slight practical advantage in having 

 the plane of vibration parallel to the vertical cross-hair. 



ENTOMOLOGY. — A new generic name for the screw-worm fly. 

 Charles H. T. Townsend, Bureau of Entomology. 



The screw-worm fly is an insect of much economic importance 

 from both the medical and veterinary standpoints. Its maggots, 

 known as screw-worms, have been repeatedly found to infest 

 diseased nasal sinuses and unguarded sores in man; while they 

 also extensively infest open sores and all cuts, wounds, or other 

 skin abrasions in cattle, horses, mules, sheep, hogs and other 

 stock, as well as dogs and various other animals. 



The screw-worm fly was originally published as Musca ma- 

 cellaria by Fabricius^ and Wiedemann.- In 1875 Rondani^ 

 erected the genus Compsomyia to include two European and four 

 East Indian species. In 1893 Brauer & Bergenstamm* selected 

 macellaria as the type of Co7npso7nyia, but this can not hold 

 since it is not an originally included species. In 1910 Coquillett^ 

 designated Musca dux Eschscholz as the type of Compsomyia, 

 which is evidently valid since there seems to have been no 

 previous designation that can hold. 



In 1863 Rondani*' mentioned Musca marginalis Wiedemann, 

 .of Africa, as the type of Desvoidy's genus Chrysomya;'' this is 

 not a strictly valid designation, as the name is not originally 

 included or designated in synonymy by Desvoidy, but Coquil- 



' Syst. Ent. 776. 1775. Syst. Antl. 292. 1805. 



2 Auss. Zw. Ins. 2: 405. 1830. 



3 Ann. Mils. Civ. St. Nat. Genova, 7: 425-427. 1875. 



^ Denkschr. Math.-Nat. CI. Kais. Akad. Wiss. 60: [91] 179. 1893. 

 ' Proc. U. S. Nat. Mus. 37: 526. 1910. 

 « Arch. Zool. Modena, 3: 27. 1863. 

 » Essai Myod. 444. 1830. 



