NO. 7 PROTECTIVE ADAPTATIONS McATEE 2.'] 



Total number of identifications, 190,919; percentage of identifi- 

 cations among those of all arthropods, 90.5891 ; percentage of species 

 in this class among the whole number of arthropod species known, 



9I-8589- 



APTERA (wingless INSECTS ) 



Protective adaptations. — The springtails and their allies appear to 

 have few adaptations such as are commonlv called protective, their 

 defense being agility in some cases, and secretive habits in others. 

 Some species haA-e coxal glands supposed to be repugnatorial. 



Bird enemies. — While only five records of Thysanura are included 

 in the tabulations here reported upon others have been made since 

 and it seems probable that birds which feed about small pools, on 

 the quiet surface of which Collembola sometimes abound, or on the 

 edges of snowfields. will be found to pay due attention to thysanurans. 



Total 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 known, .1691. 



Other enemies. — In reports of the Pennsylvania Department of 

 Agriculture and others treating the same groups of animals, seven 

 species of salamanders, four of frogs, and one toad are recorded as 

 feeding on Thysanura. Hamilton, reporting on 400 stomach con- 

 tents of young toads, says: " Collembola comprised 6.2 per cent of 

 the diet. The springtails sometimes occurred in large numbers in 

 the stomachs examined, and together with thrips appeared to be 

 an important food of all small anurans " (Copeia, 1930, p. 45). 

 Forbes reports them being eaten by a Coccinellid beetle * and a 

 small fish' {Lahidesthes siccidiis), Needham, by the brook trout,' 

 and Pearce by two species of fishes, a killifish and the mudminnow." 

 They are known to be preyed upon also by aquatic hemiptera, and 

 are cannibalistic. 



Discussion. — Thysanura are chiefly minute insects, many of which 

 spend their whole lives in well-concealed places. The forms which 

 live more or less exposed appear to have enemies among animals 

 interested in such small morsels of food. However information on 

 the subject thus far is inadequate and no doubt will be increased by 

 more intensive investigation of potential predators. 



'Bull. 111. State Lab. Nat. Hist., vol. i, no. 6, p. 52, May, 1883. 



'Op. cit, vol. 2, p. 525, 1888. 



' Bull. 68, N. Y. State Mus., p. 205, 1903. 



*Bull. U. S. Bur. Fisheries, vol. 35, p. 285 (1915-16), 1918. 



