INSECTS. 175 



Family : MuscidaB {True Flies). 



These are flies with three-jointed antennae, con- 

 structed on the type seen in the common house fly. 

 Here are included the Caterpillar Flies {Tachina), 

 the Flesh Flies {Sarcophaga), Common Flies (Musca), 

 Flower Flies (Anthomyia), Green-eyed Flies {Chlorops), 

 etc. 



The Caterpillar Flies (Tachina) 



are black, grey, or reddish yellow flies, reminding one 

 by their appearance of the common 

 house fly or the blue-bottle. They 

 play the same part in the economy 

 of nature as the sand wasps (p. 129), 

 but always lay their eggs externally 

 on the skin of the host ; the mag- 

 gots consequently never prey on ^Vcra*na7«™)' 

 those insect larvse which live in 

 the tissues of plants or in the soil. 



The Flesh Flies (Sarcophaga) 



have a longish abdomen, with large bristles on the 

 hinder margins of the segments. Thorax with three 

 longitudinal streaks. The flies suck up sweat, but do 

 not bite. The eggs develop within the abdomen of 

 the mother ; the flies lay the young larvse in dead flesh ; 

 also, if not kept clean, in wounds of human beings 

 and animals, — sometimes, too, in the genital opening of 

 horses, cattle, and swine, in which case the maggots 

 live as true parasites in the vagina and uterus, 

 causing a secretion of mucus, upon which they live. 

 Two to three generations yearly; flfty to eighty 

 maggots each time. Remedies : On keeping the flies 

 from cattle, cf. p. 165 ; to keep them from meat, fly- 

 nets, a gauze cover. Blow Fly (8. carnaria), with 

 black speckled abdomen. 



