THE CKANE-FLIES OF NEW YORK PART II 721 



ENEMIES 



Crane-flies have many enemies and but few means of combating them. 

 Every stage of the crane-fly's existence is fraught with danger. The 

 larvae of the majority of species are soft-bodied, herbivorous creatures, 

 which form a choice morsel of food for carnivorous forms of many classes 

 and orders. The period when the adult fly has just emerged from the 

 pupal hull is undoubtedly the one in which the greatest danger is found, 

 for then the insects are teneral and incapable of rapid motion. The 

 adult flies are sometimes drowned in the sea or other large bodies of water 

 and their dead fragments cast up in windrows on the shore. A very 

 unusual instance of this kind is recorded for Tipula oleracea by Patterson 

 (1908). At their best, the adult flies are poor, awkward fliers and are 

 easily captured by a wide range of species, as indicated in the following 

 pages. 



Predatory natural enemies 

 Vertebrates 



Mammalia. Undoubtedly many of the smaller mammals prey on the 

 larvae of various species of Tipula. In another paper (Alexander, 1919 d: 

 776-777) the writer has discussed the value of the larvae of an undeter- 

 mined species of Tipula in the Pribilof Islands as an article of food for the 

 arctic fox. These larvae occur in enormous numbers beneath the lichens 

 of the tundra and the foxes can easily get them at a time when other food 

 is scarce or unobtainable. Mice, shrews, and moles find an important 

 element of their food from this source. White (1914) states that in North 

 Wales the European mole, Talpa europaea, eats, on an average, twenty 

 crane-fly larvae a day, these constituting one of the main foods of this 

 mammal. 



Aves. Birds are well-known enemies of crane-flies, both in their imma- 

 ture stages and as adult flies. Hyslop (1910:129-130) lists ninety-one 

 species of birds which are known to feed on crane-flies. Baer (1913) 

 describes ravens and starlings as feeding on the larvae of a species of 

 Tipula. While working with the United States Biological Survey, the 

 writer was given the opportunity to examine files for records. His thanks 

 for assistance in this work are due to Messrs. Kalmbach, McAtee, and 

 Wetmore. The records of the Survey are based on an examination of 

 the contents of the stomachs of many thousands of individuals, and 

 furnish very valuable and fairly complete data on the North American 

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