14 



TOBACCO-WORU. PARASITE'S COCOONS MISTAKEN FOB EGOS. ITS HAPID INCKEASB. 



issue. It is not rare, tlicrefure, to meet with a worm which is thus burthened 

 and shackled ; and they arc justly regarded as g-reat curiosities. Correspond- 

 ents iiavc frequently sent nie examples of this kind; some of them suppos- 

 ing' in the fullest confidence that the little cocoons adhering to the back 

 of the worm were eggs which the worm had laid, thus demonstrating, as 

 it was thought, that the statements made in these Reports were erroneous, 

 that it is only in tlieir perfect and never in their larva state that insects 

 produce eggs. This is an error into which every one who is not acquainted 

 with insects and their wonderful habits and transformations will be very 

 apt to fall, the shape, color and size of these c<iCoons being so much like 

 eggs which a large worm like tiiis migiit be expected to generate. And it 

 shows in a strong light how important it is that our population should be 

 correctly informed and measurably intelligent in this science. For a person 

 destroying one of these worms will be particularly careful to also destroy 

 all these supposed eggs; deemin*^ that in each one of them he in effect 

 destroys another worm; instead of which he hereby protects and insures 

 the tipgrowth of another worm — thus doing the very thing which he is aim- 

 ing to prevent. 



Of the hundred flies which are bred from one of these Ichneumonized 

 tobacco-worms, we may assume that fifty at least will on an average be 

 females, to destroy fifty more worms. We thus see what efficient agents 

 these insects are in checking the increase of this moth, and what an 

 important service they hereby render us. Indeed, when we recur to the 

 fact that these parasites attain their growth in a space of time so very 

 much shorter than does the tobacco-worm, whereby' there is probably two 

 generations of them to one of the latter, it will appear that the parasites 

 issuing from a single Ichneumonized worm will suffice to destroy two 

 thousand and five hundred other worms within the time that one brood of 

 these worms is growing up to maturity. They would therefore speedily 

 exterminate these worms from existence, were they permitted to go on 

 multiplying themselves without any check. And they are so well secreted 

 and protected that there would seem to be little risk of their being dis- 

 covered and destroyed by any enemy. For during their larva state, when 

 they are soft and tender and without feet or any other means of defence or 

 escape, they are lodged within the body of the tobacco-worm where they 

 are secure from harm; and when they issue therefrom they immediately 

 enclose themselves in tough paper-like cocoons, in which thej' lie hid until 

 they have acquired wings wherewith to fly away from any danger which 

 menaces them. Thus they would seem to be protected and safe from 

 injury. Yet the artifice of enclosing themselves in cocoons fails t.' procure 

 them immunity. Another minute insect has been created and endowed 

 with the sagacity to discover them in the little pods in which they hide 

 themselves, and there this creature metes out to them the same treatment 

 which the tobacco-worm receives from them. Thus the tobacco-worm 

 does not die unavenged. The lingering, miserable death which it has suf- 

 fered, its enemies, as if by an act of retributive justice, are doomed to 

 undergo in their turn. 



