NO. 7 PROTECTIVE ADAPTATIONS McATEE I37 



specially defended groups of insects." (Trans. Ent. Soc. London 

 1906, p. 401, 1907.) 



AgnatJia, Plecoptcro, et al. — In a report which deals with the food 

 of stoneflies, mayflies, caddisflies, and Diptera in trout streams, Mutt- 

 kowski and Smith state that "Aquatic insects in rapid streams are 

 opportunists as regards food and eat whatever becomes available." ' 



Orthoptera. — Professor Poulton in the paper referred to says of 

 the prey of these insects : " The proportion of specially protected 

 forms was very high." (Op. cit., p. 408.) 



Rhynchota. — Quoting from Poulton again, he says of bugs, " So 

 far as it is possible to judge from the .... table it appears that 

 Hemiptera will prove to be extremely dangerous foes to the specially 

 protected groups." (Op. cit., p. 403.) 



Diptera. — Writing of the food of the larvae of aquatic midges, 

 A. L. Leathers says : ' " The organisms found were so similar, both 

 in number and variety, to those available in a given locality that there 

 seemed to be little or no sorting in their method of feeding." 



Professor Poulton remarks on robber flies that "A study of the 

 table at once shows that tlie Asilidae are most indiscriminate in their 

 attacks. The stings of the Aculeates, the distasteful qualities of 

 Danainae and Acraeinae, and of the odoriferous Lagria, the hard 

 chitinous covering of Coleoptera, the aggressive powers of Odonata, 

 are alike insufficient protection against these active and voracious 

 flies." (Trans. Ent. Soc. Lond. 1902, p. 336.) 



Parasites. — " Certain species and groups of species [of insecisj 

 .... have, as far as we know, relatively few parasites in any 

 region This is sometimes considered to be due to the posses- 

 sion of protective devices of certain kinds, but the explanation is not 

 satisfactory. Neither systems of colorations, nor nettling hairs, nor 

 an armour of chitinised plates, nor rapidity of movement, nor the 

 existence of toxic principles in the blood prevent insects from being 

 decimated by parasites." ^ 



Miscellaneous insects. — " Many groups of predacious insects also 

 appear especially to attack the conspicuous, easily-captured prey pro- 

 vided by the groups with warning colours. This has been observed in 



' Muttkowski, R. A., and Smith, G. M., The food of trout stream insects in 

 Yellowstone National Park, Roosevelt Wild Life Ann., vol. 2, no. 2, p. 261, Oct., 

 1929. 



" Bull. U. S. Bur. Fislieries, vol. 38, Doc. no. 915, p. 3, 1922. 



^Thompson, W. R., On natural control, Parasitology, vol. 21, no. 3, p. 279, 

 Sept., 1929, 



