ENTOMOLOGY IN OUTLINE DIPTERA. 



95 



ing the stables clean, and removing all rubbish from around the house 

 will do much to prevent them. 



The stable-fly (Stomoxys calcitrans) resembles the house-fly, but its 

 mouth parts are made for biting, while the house-fly is a sucker. Severe 

 bites, and sometimes poisonous ones, are inflicted by this insect, for 

 which the house-fly gets the blame. 



The horn-fly (Hwmatobia serrata) is another dipterous pest of 

 cattle. 



The screw-worm (Compsomyia macellaria), to which we have before 

 alluded, belongs also in this subfamily; as does the blowfly (Caliphora 

 i-omitnrici). the largest of the common species, with a deep blue, almost 

 black body, always coming in swarms when there is an odor of cooking 

 cabbage or decomposing meat. 



The subfamily Anthomyiinse is a very large one, including the cab- 

 bage-maggot, onion-fly, and many others which infest vegetation. 

 Some of its members are parasitic on other insects, and others infest 

 decaying vegetation. Some of these resemble house-flies, but differ 

 from them in structure. 



The second division of the Muscidse is the Aealyptrate Museidse, and 

 thi> includes the fruit-flies, the dreaded Tryp.eta hi dens among others. 

 Must of the flies 

 belonging to the 

 subfamily Trypet- 



inae are small, al- l^jj^r J /[\ 



though some of "2fillfcr -/! \ 



them are at least 

 medium in size. 

 They are charac- 

 terized by their pe- 

 culiar wing mark- 

 ings, which are 

 shaded, mottled, 

 banded, or striped. 

 They vary in color 

 from light brown 

 to nearly black, and the family is well represented in the United States. 

 It must not be supposed that because T. ludens, T.pomonella, and several 

 others of our fruit pests belong to this family, all are pests on fruit. 

 It is true that most of the fruit-flies belong here, but a very large 

 number of the species live in galls which they form in the stems of wild 

 plants, and are not noticeably injurious. 



The cheese-maggot (Piophila casei) belongs in this group, as do also 

 the vinegar or pomace flies small, yellowish flies, common about 

 decaying fruit. 



FIG 



Trypeta acidusa. Puparium at right, adult at left, greatly 

 enlarged. (After Howard.) 



