42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



be made to the special and curious defence by a waxy secretion which 

 is common in the Homoptera. The method may be compared to the 

 defensive silken walls of the cocoon in other insects, while the long 

 trailing filaments of wax borne by certain species of Homoptera may 

 play the same part as the ' tails ' on the hind wings of many Lepidop- 

 tera, or the ' tussocks ' of hair on some of their larvae — all these 

 probably acting as directive structures which divert the attention of 

 an enemy from the vital parts." 



Many plant lice have the waxy filaments alluded to by Poulton, 

 while most of them exude special secretions from the cornicles, sup- 

 posed to be protective. Leafhoppers of various groups have been 

 thought to resemble color or structural details of plants they frequent, 

 and as for scale insects, their small size, waxy secretions and great 

 resemblance to the bark upon which they rest, have given them high 

 rank among the theoretically protected insects. Indeed they have been 

 thought well-nigh immune to attack and one author has intimated that 

 birds never eat scale insects. (Smith, J. B., Proc. State Hort. Soc. 

 N. J., vol. 29, p. 90, 1904.) 



Bird enemies. — Below are tabulations of the identifications of 

 Hemiptera in the stomach contents of nearctic birds followed by sup- 

 plemental comment. Comparative percentages are not given for the 

 plant lice, scale insects, and mealybugs as these have not been cata- 

 logued with the same degree of thoroughness as the other groups. 



Total number of identifications of Hemiptera, 22,395 ; percentage 

 of identifications among those of all insects, 11. 7301 ; percentage of 

 species in this order among those of all insect species known, 8.5899. 



The Corixidae, although they spend practically all of their existence 

 in water and usually on the bottom, do not thereby secure immunity 

 from bird enemies. 



Like other hemiptera, however, they are supposed to be specially 

 protected, one author saying : 



As to the function of the stink-apparatus in the adult Corixa, there is no 

 need to look beyond defence. The insect frequently leaves the water, and it is 

 then exposed to all the dangers met with by the land Heteroptera. Also there 

 is no reason to doubt that the odoriferous secretion is equally efficacious against 

 enemies in water.* 



Results indicate that this efficacy is nothing remarkable ; indeed it 

 is a fallacy to suppose that so abundant and accessible a group does 

 not pay due toll to predators. The number of species of birds that 



* Brindley, Maud D. Haviland, On the repugnatorial glands of Corixa, 

 Trans. Ent. Soc. London, vol. 77, p. 13, 1929. 



