272 ECONOMIC ENTOMOLOGY 



Eggs. ^Laid in an irregular heap of about 100 on manure and gar- 

 bage; similar in form to those of House-fly; hatch in 2-3 days. 



Larva. — Similar in form to that of House-fly, but more trans- 

 lucent in appearance. Duration 10-20 days. 



Pupa. — Duration 6-20 days; puparium reddish-brown, elongate- 

 oval, }i inch long. 



This fly occurs in the open, but often enters houses; breeds rapidly 

 in oat-straw and other organic refuse. Winters as pupa or larva. 



Control. — Apply 0.62 lb. borax to every 10 cu. ft. (8 bushels) manure, 

 on removal from stables, with a flour sifter or fine sieve, particularly 

 about the edges of the pile, and sprinkle 2 or 3 gal. water over the 

 heated manure; use fly-traps. (Consult Farmers' Bulls. 540, 734 and 

 851, U. S. Dep. Agr., 1913.) 



Horn Fly {Hcematobia serrata ^oh. -T>es,v.,Lyperosia irritans'Lm.n.) . — 

 (Consult Circ. 115, Bur. Ent., U. S. Dep. Agr.) Introduced into 

 U. S. about 1886 from Europe, and has spread rapidly since. 



Adult. — Similar in shape and color to House-fly, but about half as 

 large. June-September. 



Eggs. — ^Laid singly in fresh cow manure in day time, irregular, oval, 

 light reddish brown. Egg-laying begins soon after adult emerges. 



Larva. — White, 14 i^^ch long; full grown in 4-6 days. 



Pupa. — Puparium dark brown, ellipsoidal, 36 i^^h long; pupal 

 stage lasts 5-10 days. 



Probably 6-8 generations in a season. 



Control. — (i) Killing the maggots by the introduction into the man- 

 ure of Hme and other drying and destructive agents; (2) application of 

 creolin compounds in the form of spray, or kerosene emulsion solution, 

 or a mixture of 3^^ gal. fish oil, Yi pint coal oil, 4 tbspfls. crude carbolic 

 acid applied with a cloth rubbed over the parts attacked. 



The main factors limiting the number of the common flies are: 



(a) The destruction of the larvae and pupae by braconid and chalcid 

 parasites; 



{h) The lack of food for the larvae; 



(c) The enemies of the adults; 



{d) Weather conditions — oppressive sultry weather; cold, wet 

 and windy weather; acting on the adults, and preventing the emergence 

 of adults from the pupae. 



