16S THIRD ANNUAL REPORT OF 



seems to be no record of any person having actually seen a bird or 

 other animal attack the species of Limenitis in this country, there 

 is every reason to believe that they will do so. This fact once being 

 admitted, it must also be admitted that the resemblance of Dinppus 

 to Archippus serves the former as a protection. I freely grant how- 

 ever, that the species of Limenitis are kept under by enemies far 

 more in the preparatory states than in the perfect state; but this fact 

 only adds importance to the mimicry of Dlsippus as throwing light 

 upon its greater numbers. The larvre and pupae of Ursula and Di- 

 sippus so closely resemble each other that it is not likely their ene- 

 mies would make any discrimination between them; and if in a given 

 district where Archippus is abundant, the two former species, by the 

 undue multiplication of their enemies in some particular year, should 

 be so thinned out while in the immature states, that only a dozen 

 imagines of each were perfected in an area of say 100 square miles; 

 it becomes obvious that by deceiving the birds, or by associating with 

 Archippus, the twelve specimens of Disippus would stand a much 

 better chance of escape than those ot Ursula, and that consequently 

 more would succeed in perpetuating the species. 



[3.] Natural Selection does not, therelore,waste its energies upon 

 unimportant material, in giving protection to the perfect insect; and 

 any one, with a little reflection, will perceive that there are the best 

 of reasons why the unfortunate caterpillar of Limenitis cannot 

 mimic the more favored larva of Danais. They never come in con- 

 tact ! The perfect insects are enabled by flight to associate together; 

 but their larvre— the one being confined to plants of the Willow and 

 Poplar families, the other strictly to those of the Milkweed family — 

 can never so associate. That there is, however, an effort at protec- 

 tion in the preparatory stages of Limenitis, no entomologist who has 

 studied them in the held will deny. The egg, as Mr. Scudder has 

 admitted, is in a measure protected by the long filamentous spines, 

 which may protect it from the attacks of some of the very numerous 

 parasites that might otherwise aid in exterminating it. The larva is 

 very variable, and wears a remarkable protective resemblance to its 

 surroundings. I have often noticed that in the mature specimens 

 found on the dark Scrub willow the dark colors predominate; that 

 those found on Golden willow are much brighter and greener, and 

 the palest specimen I ever saw was found upon Silver poplar. Only 

 those who have diligently searched for these larva can fully appre- 

 ciate the protection which their appearance affords. In one instance 

 I chanced to espy a large full grown specimen of Disippus on a Golden 

 willow not more than seven feet high. The specimen on account of its 

 brightness and greenness struck me as remarkable, and 1 searched 

 for others. In taking a casual glance I could detect none, but after 

 a diligent search I succeeded in finding seven specimens, and then 

 left, fully convinced that I had espied every one upon the tree. The 

 .next day, however, my confidence in the sharpness of my eyes was 



