102 SATURDAY LECTURES. 



Let US take for examples the large Potato- worm or any 

 other Sphinx larva with the horn near its end (which seems 

 to have no other purpose that to frighten superstitious 

 people who erroneously believe it to be capable of inflicting 

 a })oisonous sting,) and one of its commoner Ichneumon para- 

 sites belonging to the genus Microgaster. Our female Ichneu- 

 mon-fly hovers about the worm while it quietly feeds. Set- 

 tling finally on its back, generally behind the head where 

 its mouth cannot reach her, she deliberately thrusts her ovi- 

 positor through the skin of her victim and oviposits within 

 its body. Ilcr young are soft, whitish larvEe which, ujDon is- 

 suing, spin upon the poor worm's back a number of egg- 

 shaped cocoons (Figure 13,) often mistaken for eggs by the 



Fig. 13. — Shrunken larva of Cha'rocampa pampinatrix, with Microgaster co- 

 coons. (After Harris.) 



uninitiated. Within these the transformations are under- 

 gone, and the perfect flies cut a lid through the top of the 

 cocoon and escai)e, sometimes while yet their victim shows 

 faint signs of life. Now such a parasitized worm will drag 

 out a paralyzed kind of existence without food for several 

 wrecks, where, normally, it would starve to death in as many 

 days, and the parasite may, in its turn, be infested with a 

 secondary species, etc., as above stated. 



THE MOSQUITO. 



There is another little lady whom you have fed and re- 

 galed at your own expense, and very unwillingly withal. 

 She is by no means modest, but steals unbidden into your 

 room. She generally heralds her coming with song that is 

 anything but soothing, and she is so persevering that even 

 the strong " bars " with which you protect j'-ourself are not 

 proof against her persecutions. You have all, no doubt, at 

 times exercised a little strategy with the mosquito, and 



