11 



TODACCO-WOnM. KILLED BY INTEnNAL PAnASITES. TDEin BABITS. 



to tlie body, and reach two-thirds of its length, and interposed between 

 them at their ends is a single pair of the leg-sheaths, which exactly equal 

 them in length. Along their lower edges are the antenniE-shcaths, regu- 

 larly marked with transverse impressed lines, and tapering to a very acute 

 point on each side of the end of the tongue-case. The rings of the body 

 are closely and confluently punctured on their anterior sides and show 

 numerous transverse irregular scratches and fine wrinkles towards their 

 posterior edges. The breathing pores form a row of oval impressions 

 along each side, each having two acutely elevated lines and between them 

 a narrow elliptic cleft. On the back at the base of the al)domen is a 

 smooth black transverse ridge interrupted in its middle. The three short 

 rings at the hind end are rapidly narrowed, forming a conical point havin"- 

 at its tip two small thorn-like points, one larger than the other. 



We come in the next place to consider the natural enemies and destroj'- 

 ers which restrain this insect from becoming excessively multiplied and 

 numerous. Large and vigorous as this tobacco-worm is, enveloped in such 

 a tough, leathery skin, and j('rking its body about with the force and spite- 

 fulness it does when anything molests it, we should scarcely suppose any 

 other creature would care to encounter it. And yet it finds its mortal foe 

 in a little four winged fly, scarcely a thousandth part of its size. It is truly 

 wonderful that such a pigmy as is this fly is able to attack and destroy 

 such an elephant as is this worm. The fly alights upon the worm, and with 

 the short sting or ovipositor with which it is furnished pierces its skin and 

 inserts a minute egg in the puncture. It continues to repeat this opera- 

 tion at one point and another upon the back and sides of the worm, until 

 its whole stock of eggs, amounting to a hundred or more, is exhausted. 

 These eggs hatch minute maggots, which distribute them.selves all through 

 the body of the worm, feeding upon its fatty substance, but without attack- 

 ing any of its vital parts. And thus the worm continues industriously to 

 feed and elaborate nourishment for feasting and pampering these greedy 

 parasites which are luxuriously rioting within it. If a worm which is thus 

 infested be cut into, it appears to be everywhere filled with these little fat 

 mtiggots. When they have got their growth they gnaw out through the 

 skin, but instead of dropping to the ground and there secreting themselves 

 as thoy would be expected to do, they still cling to the unfortunate worm, 

 each maggot spinning for itself a little oval white cocoon, one end of which 

 it fastens to the skin of the worm at the orifice where it has issued from 

 it. Thus the worm comes to present the remarkable spectacle of being 

 clothed, as it were, with a hundred or more of these cocoons, resembling 

 little white seeds like kernels of rice adhering to and in places wholly cov- 

 ering its back and sides. I have counted one hundred and twenty-four of 

 these cocoons upon a single worm, and a still larger number will probably 

 be found in some instances. 



Th(!se parasitic cocoons are milk white and of a regular oval form, 0.15 

 long and 0.06 broad. Their walls are no thicker than thin writing paper, 

 but are very dense and firm. Their surface is minutely uneven, with a few- 

 loose, wrinkled threads at one end, whereby they are held to the skin of 



