84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



the large families of Coleoptera, those abundant in individuals, are 

 most freely eaten by birds, while the small families with few species 

 escape with small losses. It is the old story over again of food sup- 

 pHes (beetles in the present consideration) being drawn upon in pro- 

 portion to their abundance and availability. 



MECAPTERA (SCORPIONFLIES) 



Protective adaptations.— The scorpionflies are predacious ; those of 

 the genus Panorpa commonly have yellow bodies and black markings 

 in the wings ; and the males have enlarged genitalia carried aloft some- 

 what like the stings of scorpions. The species of Bittacus resemble 

 crane flies. 



Bird enemies. — We have only five records of scorpionflies being 

 eaten by nearctic birds, these being distributed among four species. 



Number of identifications, 5 ; percentage of identifications among 

 those of all insects, .0026 ; percentage of species in this group among 

 the whole number of insect species, .0260. 



Other enemies. — There seem to be no records of such. 



Discussion. — Poverty of data is the chief characteristic of the record 

 for scorpionflies. These insects are not an obtrusive part of the insect 

 fauna and have been little studied. The question of the efficiency of 

 their protective adaptations in relation to predators can hardly be 

 intelligently discussed at present. 



DIPTEEA (flies) 



Protective adaptations. — Not much has been written about the pro- 

 tective adaptations of diptera, the suggestion most often made being 

 that a considerable number of them " closely resemble wasps, and bees, 

 and no doubt derive much benefit from the wholesome dread which 

 those insects excite." (Wallace, Natural selection, p. 69, 1891.) The 

 families that have the most numerous species supposed to resemble 

 Hymenoptera are the Stratiomyidae, Bombyliidae, Asilidae, Co- 

 nopidae, and Syrphidae. Many flies have metallic colors, which are 

 alleged to be warning; such insects are common among the Stratio- 

 myidae, Dolichopodidae, Tachinidae. and Muscidae. A large number 

 of Diptera pass the greater part of their lives in the larval stage and 

 many of these larvae are more or less protected from birds by their 

 habitat, as the Cecidomyidae in galls, the Mycetophilidae and others in 

 fungi, the Culicidae, Chironomidae, many Tipulidae, the Simuliidae, 

 Stratiomyidae, Tabanidae, and I^phydridae in mud or water ; and 

 various others in excrement and other decaying organic matter. Of 

 course this sort of protection is of no avail in the case respectively of 



