STATE HORTICULTURAL SOCIETY. 



"5 



appeared in the Eastern States the native potherb-butterfly {P. oleraced) 

 at once began to disappear ; and now our P. protodice is rapidly giving 

 way before it. 



In what does its aggressive power consist ; and what peculiarity is 

 there in its life or composition that renders it capable of becoming thus 

 cosmopolitan? These are difficult questions to answer, but they must be 

 answered before the life-history of the species can be fully written. 



A remarkable difference in habits between very closely allied species 

 is often unaccompanied by any appreciable difference in external anatomy 

 or markings. Our common red-legged locust {Caloptenus femur ■rudrum') 

 is so nearly allied to the destructive Western species (C spretus) that it 

 is difficult to distinguish the one from the other; and there is still an inter- 

 mediate species (C. Atlantis). Yet the Western species is truly migratory, 

 while the others are not. Still more closely allied are Acridiuvi peregrinum 

 (illustration referred to) and A. americanum (illustration referred to), yet 

 the former is the destructive species of the tropical regions of the 

 Eastern continent, and is even found in America, while the latter is 

 found in the southern part of our own State non-migratory. The only 

 characteristic difference in the two cases is found in the form of the last 

 abdominal segment of the males. Shall we ascribe such remarkable 

 differences in habits to this small anatomical variation in one sex? 



The army-worm is a true cut-worm, although not appertaining to 

 what is usually called the cut-worm genus. 



What gives rise to its migrating habit, which is not found in other 

 species? I have even seen two different broods of the same species 

 exhibiting the two different characteristics the same season ; the one as 

 an army marching near a grassy plat, where the other as a cut-worm, hid 

 from view, was cutting the grass until the sward could be rolled up as a 

 carpet. Why this difference? Is it because of excessive numbers? But 

 why does the other species never develop in such excessive numbers? 

 The answer only carries the difficulty one step farther back. Will you 

 answer, that such facts are not uncommon in the history of the animal 

 kingdom? But this brings me no nearer to a solution of the problem. 

 The why — the reason for this — is what I desire. 



But let us return to our cabbage-worm, for we shall be sure to find 

 one the gardener has overlooked. 



Admonished, doubtless by some peculiar feeling, that the time for 

 some great change in its life has come, it becomes uneasy and seeks 

 some place of retirement. How far it is conscious what this change is to 

 be we know not; but that it is aware something unusual is about to take 

 place is evident from its uneasy movements. Having found a suitable 

 place under some projecting board or rail, it spins a little silken mat on 

 the surface to which to attach its feet; next it spins a strong thread 

 across the middle oT its body, attaching it firmly to the plank on each 

 side (calling attention to the figure). These are to serve as supports 

 when it is in a semi-torpid state and its legs shall have disappeared. 

 How it is aware that this is necessary science can only answer by tlic 

 meaningless word — instinct. 



