1920] MetcalJ: Diptera 187 



THE ADULT. 



The adult stage is usually short lived, but is quite variable 

 in the different families, and may even vary greatly in the same 

 species, depending on the success of mating, feeding, etc. It 

 is believed that in some species (Culicidas, Oestridae, etc.) the 

 adults normally live only a few days and many forms probably 

 never feed. Others lead a very active and vigorous life for 

 some weeks or months as Trypetidas, Drosophilidae, Anth- 

 omyidae, Muscidae, Tachinidae, Hippoboscidae, etc. Certain 

 adults have been kept alive well over a year. 



Their haunts are almost as varied as those of the larvae. 

 Two conditions are especially favored: 



(a) The vicinity of water in which the immature live. Here 

 are found many Tipulidse, Dixidas, Chironomidae, Bleph- 

 aroceridae, Ephydrid^, Cordyluridae. 



(b) Sunlight, which is especially effective on the activities 

 of Tabanidae, Syrphidas, Bombyliidae, Conopidas and 

 others. 



The location of their own food is of course a dominating 

 factor. The most noteworthy point regarding the food of 

 adults is the complete specialization away from the primitive 

 habit of defoliating plants. A very great number of species 

 secure their food from flowers. The Tipulidae, Culicidae, 

 Stratiomyidas, Tabanidae, Bombyliidae, Syrphidae, Conopidae, 

 Anthomyidae, Muscidae and Tachinidae, are generally flower- 

 feeders on nectar, or pollen, or both. Many species can feed 

 on liquid organic matter or dissolve solid substances and sponge 

 them up. 



Species of the families Blepharoceridas, Leptidae, Asilidae, 

 Therevidae, etc., are predaceous on small insects. In two 

 families, the Tabanidae and Simuliidae, almost without exception, 

 the females suck the blood of warm-blooded animals. Six 

 other families are known to contain blood-sucking species — the 

 Culicidae, Chironomidae, Psychodidae, Muscidae, Leptidae and 

 Hippoboscidae. In only one family, the Muscidae, do we find 

 blood-sucking males, the males of the other families generally 

 feeding on pollen, nectar, etc. Some of the Muscidae feed on 

 blood drawn by other insects (not being capable of drawing 

 blood themselves) by inserting their proboscides at the side of 

 those of their piercing relatives. A curious habit is recorded 



