218 



NATURE-STUDY REVIEW [13:6— Sept., 1917 



THE ECONOMIC IMPORTANCE OF BUTTERFLIES 



For the most part butterflies are not injurious; although while 

 in the caterpillar stage they feed upon vegetation, most species 



live upon weeds of 

 various kinds, and 

 those that feed 

 upon the leaves of 

 trees rarely occur 

 in such numbers as 

 to do damage. The 

 cabbage butterfly 

 is a notable ex- 

 ception ; it came 

 to us from Europe 

 and is now a wide- 

 spread pest that 

 would work de- 

 struction to the en- 

 tire crop of cabbage 

 and other crucifer- 

 ous garden plants 

 if left alone. The caterpillars of the black swallowtail occasionally 

 occur in sufficient numbers to damage celery, and the young of the 

 giant swallowtail do injury to the foliage of orange trees; occa- 

 sionall'v the caterpillars of the mourning cloak do some damage to 

 elms. However, all butterfly caterpillars are easily gotten rid of 

 by spraying the foliage on which they are feeding with poisoned 

 water. The benefits conferred by butterflies are only partially 

 known and little appreciated. Ver\^ many flowers depend upon 

 butterflies for carrying and bringing pollen. The black swallow- 

 tail is especially beneficent in this respect. A large number of the 

 species assist in cross pollinating the flowers of the plants on which 

 their }^oung feed and thus they pay back their debt. One little 

 radical, the wanderer, has departed from the traditions of the 

 butterfly family; its caterpillar feeds upon plant lice and thus is 

 very helpful. 



The Black Swallowtail 

 Expanse three and one-half to four inches. Color 

 brownish-black, the front wings spotted with yel- 

 low, the hind wings bearing yellow and blue spots. 

 There is a red eye-spot at the inner angle of the 

 hind wing. 



