November, 1920] 



The Canadian Field-Naturalist 



151 



anterior margin. On the ventral surface of the basal Color the same as in the female except that the 



jomt of the third legs is a broad flap, projecting black spots on the dorsal surface are larger and 

 backwards, and on the anterior margin a rounded more scattered, 

 knob armed with minute setae. 



Total length 4 mm. Carapace 3 mm. long, 2.65 



mm. wide. Abdomen 1 mm. long, 0.80 mm. wide. 



(piperatus, sprinkled with pepper, alluding to the 



black spots). 



The types of this species are deposited in the 

 Museum of the Atlantic Biological Station, St. 

 Andrews, N.B. 



Fig. 7. Argulus piperatus; fourtti legs of male; 

 much enlarged. 



BIRDS IN RELATION TO INSECT CONTROL. 

 By Norman Criddle, Entomological Laboratory, Treesbank, Man. 



The value of birds to mankind has unfortunately 

 been brought down to the level from which we 

 guage most things nowadays, namely, dollars and 

 cents. We might in the past, have classed them with 

 art, poetry and music, but to-day the aesthetic sid; 

 IS lost in the mad rush for wealth and those of us 

 who still value wild life for what it is, rather than 

 for its economic significance, are obliged to weigh 

 its qualities by the standard which modern thought 

 demands. 



The value of birds in relation to agriculture is a 

 question that has frequently been discussed. The 

 value of birds as destroyers of noxious insects is 

 usually linked with the preceding problem though 

 experts are not as unanimous in their conclusions 

 regarding this part of the question, adverse conten- 

 tions being especially strong among Italian ento- 

 mologists who are apt to disclaim any assistance 

 from birds to agriculture or kindred sciences. The 

 Italians have their school of followers in North 

 America but they are fewer. Since, however, 

 they are men of ability it seems well to look rather 

 more fully into the reasons for these differences of 

 opinion. 



Probably the first obstacle to unanimity lies in 

 the fact that two sciences are involved namely 

 ornithology and entomology whose voteries, on the 

 whole, have but a superficial knowledge of each 

 other's work. For instance, the ornithologist may 

 be well aware that birds eat insects but he does not 

 always know that the insects consumed may con- 

 tain within them those that are useful. The entom- 

 ologist en the other hand, knows little of the habits 

 of birds and is, therefore, apt to view the question 

 wholly as an insect one and to depend upon insects 

 for insect control arguing that birds in eating a 

 single noxious insect may destroy half a hundred 

 useful ones, and so prevent the spread of allies that 



would control a pest far more quickly than birds 

 could, even supposing the latter were able to ac- 

 complish the task at all. 



The first point to accept in this discussion is that 

 insect extermination is cut of the question. The 

 problem is not how to exterminate a pest but it is 

 rather to secure the best means of keeping it within 

 bounds. 



I believe we shall eventually reach the conclusion 

 that insect parasites are of most value in controlling 

 serious outbreaks while birds reach their greatest 

 usefulness by destroying the surplus under normal 

 conditions and so prevent outbreaks. Neither of 

 these differences in value are clearly defined, how- 

 ever, as a great many minor issues are involved in 

 the whole question some of which I give below. 



The rapid increase of an insect pest is due to 

 several causes among which the absence of parasites 

 is an important one. Under these circumstances the 

 chances of birds destroying useful parasites in feed- 

 ing upon the host at that time, is small, while by 

 devouring the increasing pest they are playing an 

 important part in keeping it within bounds. Occa- 

 sionally, however, the pest increases beyond the 

 rate at which birds can check it, this being due 

 largely to meteorological conditions. At such times 

 neither parasites nor birds are of much value and 

 the pest spreads over wide areas as was exemplified 

 in the grasshopper outbreak of the last two years in 

 the Prairie Provinces. It is at this point that birds 

 fall behind and parasites usually come to the fore 

 and as these last have now unlimited food available 

 they multiply with great rapidity. It matters little 

 under these circumstances, whether birds devour 

 parasites or not as the latter are too widely spread 

 to be affected. Indeed the ultimate result is for the 

 parasites to become over abundant in which case 

 they are reduced to insignificance by starvation due 



