258 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1934 



DECREASE IN CERTAIN SPECIES OF INSECTS 



Some insects are less plentiful now because of these agricultural 

 activities and because of the incidents connected with the progress of 

 civilization. The periodical cicada has been adversely affected by 

 civilization. The great swarms rending the air with their shrill 

 music and causing bushes to bend under their weight will before 

 many generations exist only in story. Bumblebee nests are much less 

 frequently encountered during ordinary farm operations than was 

 the case 30 years ago. Civilization has been unfavorable to bumble- 

 bees and to field mice whose nests are often used by the bumblebees 

 for making their nests. Outbreaks of grasshoppers are becoming 

 less frequent in Kansas because of improvements in control measures 

 and of decreasing areas of suitable breeding places. Grasshopper 

 outbreaks are not characteristic of areas of intense cultivation on 

 small farms and gardens. 



Such insects as the spring canker worm, which 30 or 40 years ago 

 defoliated orchard and shade trees almost unchecked, have been re- 

 duced by spraying for the codling moth, a more serious and more 

 recent pest. Likewise, dusting cotton for the cotton boll weevil has 

 relegated the less serious pest, the leafworm, to a minor place in some 

 of the cotton-growing areas. Thus artificial control measures for the 

 more serious pests have reduced some secondary ones also. 



Invention even enters in here, for collectors of dung beetles say 

 that some species of this group of Scarabs are not so easy to collect 

 since the decrease in the use of horses in transportation. One won- 

 ders, when he sees radiators of automobiles plastered with insects, 

 especially butterflies, dragonflies, and grasshoppers, whether this de- 

 vice of modern civilization might not become a more important 

 factor in the reduction of populations, both insect and vertebrate.^ 



Sanitary and health measures have brought about a probable 

 reduction in many forms of importance in the field of medical ento- 

 mology. Extensive paving of roads and streets, river improve- 

 ments, better drainage on farms and cities, together with the exten- 

 sive propaganda about mosquito-borne diseases, have kept down mos- 

 quitoes, particularly in cities, except for sudden increases following 

 periods of heavy rains. The great reduction of horses in cities has 

 reduced fly-breeding opportunities. The widespread understanding 

 of food contamination has placed the typhoid fly on the public 

 enemy list. 



Parasitic forms dependent on wild animals become less plentiful 

 as their hosts decrease, unless they select new ones. The hippoboscid 



• Fernald, H. T. Automobile as an insect collector. Bull. Brooklyn Ent. Soc, vol. 26, 

 no. 5, pp. 231-233, 1931. 



