TABLE OF CONTENTS TO REPORT IV. 25 



Page. 

 Two of our Common Butterflies Continued. 



THE DISIPPUS BUTTERFLY 153 



Distinguishing characters of the Nymphalidse, 153 Food plants and geo- 

 graphical range, 153 The egg, 153 Description of the egg, 154- 

 Developineut of the larva, 154 Description of the mature and young 

 larva, 154 The insect hibernates as young larva, 155 Case prepared 

 by the larva for its winter quarters, 155 Modifications of the case, 

 156 Peculiar habit of the autumnal larva>, 156 Parasites, 157 Ta- 

 china-fly, 157 The Disippus egg-parasite, 157 The Disippus Micro- 

 gaster, 158. 



MIMICRY AS ILLUSTRATED BY THESE TWO BUTTERFLIES, WITH SOME REMARKS 

 OX THE THEORY OF NATURAL SELECTION 159 



Conformity of color between animals and their surroundings, 159 Defi- 

 nition of the term "mimicry," 160 Pungent odor possessed by the 

 Dauaidd', 160 Their mode of flight, 160 Protection they derive from 

 their peculiar odor, 161 Pieridw and Danaidtu in the Valley of the Ama- 

 zon, 161 Mimetic forms of Fierida', 161 Explanation of the origin of 

 mimetic forms, 162 Mimicry between the Archippus and Disippus 

 Butterflies, 163 The Ursula Butterfly, 163 Its caterpillar and chry- 

 salis uudistiiignishable from those of the Disippus, 163 Its imago has 

 no protective color, 164 Mr. Bennett's objections to the theory of Nat- 

 ural Selection producing mimetic forms, 165 Mr. Scudder's objections, 

 166 Discussion of Mr. Scudder's arguments, 167 Mr. Murray's ob- 

 jections to the connection between mimetic resemblances and Natural 

 Selection, 170 Natural Selection not the only power producing mim- 

 icry, 171 Reasons for discussing in this Report the theory of Natural 

 Selection, 172 Natural Selection involves belief in the doctrine of 

 Evolution, 173 Darwinism is neither irreligious nor atheistic, 174. 



REPORT IV. 



[Submitted December 2, 1871; published April, 1872.] 



Preface 



NOXIOUS INSECTS. 



Notes of the Year 



THE COLORADO POTATO-BEETLE 



Its injuries in 1871, 5 Its appearance in great numbers in early spring, 

 5 Exorbitant price of Paris green, 6 Natural enemies of the beetle 

 very abundant, 6 Diminution in numbers of the beetle later in the 

 season, 7 Causes of such diminution, 7 Damage caused by the Potato- 

 beetle in Missouri, 7 It invaded Canada in 1870, 8 The Three-lined 

 Potato-beetle mistaken for it in New York and Massachusetts, 8 Its 

 further spread eastward irresistible, 8 Slow spread of the insect in the 

 South, 9 Its present extent northward, 9 It spreads but does not 

 leave the districts already invaded, 9 It is not injurious to potatoes in 

 Colorado at a certain altitude, 10 New food-plants, 10 It feeds upon 

 cabbage, 11 Its hibernation, 11 Objections raised against the use of 

 Paris green, 11 Paris green is an efficient remedy and now in general 

 use, 12 Box for dusting Paris green, 12 Mixing the poison with di- 

 luents, 12 No serious cases of poisoning have come to knowledge, 13 

 Antidote for Paris green, 13 Other applications, 13 Messrs. Saun- 

 ders's and Reed's experiments with various substances, 14 Experiments 

 with decoctions of various plants, 15 Air-slacked lime as a remedy, 15 

 Mechanical means, 15 Squire's Brushing machine, 15 Creighton's 



