G36 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Words fail to des<;ribe their geueral depravity ; it is beyoud expression. 

 If you wish to be happy, be sure you dou't introduce cluster flies into 

 your fiimily." 



The flies are also stated to be very sluggish — crawl rather thau fly 

 away when disturbed ; hang from the cornice of a room in large clusters, 

 like swarming bees, which can be brushed bodily into a vessel of boiling 

 water; under buildings between earth and floor they are often found in 

 incredible numbers ; crawl in quiet, dark rooms between the sheets and 

 under the i)illows and vallances of made-up beds, and under the nailed- 

 dov,-u edges of carpets, leaving nasty spots and a disagreeable smell 

 wherever they go. If windows and blinds are opened and the room is 

 occupied, they quietly vacate the premises in a little while unless they 

 can crawl into some closet or wardrobe. There are in geueral appear- 

 ance very like the common housefly, but heavier-bodied, somewhat 

 larger and more hairy — in short, coarser-looking. 



Professor Riley writes as follows: 



''So far as I have been able to investigate the matter your fly is the 

 Musca famiUaris of Harris (Ent. Corresp., p. 33G), synonymous, without 

 much question, with the Musca r?^(7/s Fabricius. It is not uncommon in 

 New England in houses, nearly disappeariug when M.domesticn most pre- 

 vails and found most in spring and fall. But I find no account of its 

 abundance and annoyance in the manner you describe. It belongs to 

 the genus PoUenia Eobineau-Desvoidy." 



"CLUSTER FLIES." 



The fly presented by Mr. Dall at a previous meeting is the Musca 

 rudis of Fabricius, a species known to be common to Europe and Amer- 

 ica* and redescribed, as Musca famiUaris, in this country by Harris,t 

 who says of it: "This species, not uncommon in houses in summer, 

 nearly disappears the more abundant M. harpyia prevails. It resem- 

 bles M. rudis Fabr., but is larger than the only specimen I have seen, 

 and has the thorax much more densely clothed with fulvous hairs. 

 From M. harpyia [M. domestica C. V. E.] it diflers in the superior size, 

 in having the eyes coutiguoifs in the male, in the prominence of the 

 front, in the hairiness of the thorax, etc. 21. obscura of Fabricius is 

 also synonymous, according to Meizers, who says of it (vol. V, p. OG) 

 " Ein altes verwischtes Exemplar von 21. rudis.''^ It belongs to the genus 

 PoUenia of Eobineau Desvoidy, who made it, in fact, the type of that 

 genus. This author in his " Histoire des Dipteres des Environs de 

 Paris," (vol. II, p. GOO), mentions about 40 species of PoUenia, and says 

 of rudis: "It becomes very common in autumn, and the first frosts 

 compel it to take possession of our apartments. It here accumulates 

 in numbers in the embrasures of windows and in the recesses of walls; 



*Cf. Loew's note on this subject in liis Ueber die Dipterenfauna des Bernstein's 

 (translation in Sill. Journ. Sc. & Arts., vol. xxxvii, 2d ser., p. 318). 

 tEntomol, Corresp. of T. W. Harris, p. 3:^6. 



