the walls of the pitchers and prevent these larvae from being wedged fast in the tapering 

 cavities they inhabit; whereas the caterpillar of rolandiana, living in the squat, open- topped 

 pitchers of purpurea, does not so greatly need nor does it possess these appendages. 



Thus instinctive and structural adjustments make possible a relationship between insect 

 and insect-eating plant, entirely to the plant's disadvantage; and the conclusion seems inevitable, 

 that although the plant has brought its trap structure to such perfection that few insects may 

 escape it, yet the pitcherplant moths, in their evolution, have met these dangerous conditions 

 and have actually turned them to their own advantage. 



PITCHER ROBBERS 



In nature, the usual response to any concentration of potential food supply is a flocking in 

 of claimants for that food; so that it is to be anticipated that the store of animal matter 

 accumulated in the pitchers of Sarracenia, when once their traps become operative, should 

 attract other animals, and that some of these should evolve methods of eluding the trap and 

 of securing for themselves a portion of that food. These pitcher robbers are of a number of 

 species, and some of them are so permanently adjusted to life as associates of the pitcherplants 

 that they have lost the ability to survive under any other conditions. For example, no sooner 

 have captured insects begun to accumulate in the pitchers than among the dead and dying 

 insects we may usually find one or several living whitish maggots, which in fluid-filled pitchers 

 wriggle their way up to each fresh capture and commence to feed upon it as it floats on the 

 surface. The larger of these maggots are the young of the Sarracenia flies, genus Sarcophaga, 

 with at least six species having this habit and habitat. As young maggots, they are deposited 

 within the pitcher's mouth by the parent fly. Feeding upon its captures until they have 

 attained larval maturity and a length of about three-quarters of an inch, they then usually 

 leave the pitcher and change to brown puparia in the sand or moss at the base of the plant. 

 From these puparia in due course emerge adult flies, which continue the life cycle as before. 



These insects, throughout their stages, seem to possess no structural adaptations to fit 

 them for life in their dangerous habitat; but like the pitcherplant moths, they know their 

 way in and out of the pitchers and rarely fall victim to the trap. They confer no benefit 

 upon the plant in compensation for their robbery of it, unless the habit of the flies of crowd- 

 ing into the flowers at night and on stormy days may give them status as pollinizers, to which 

 office their appropriate size and their bristly integument seem to fit them. One remarkable 

 character of these larvae may have originated as a needed defense, for like the intestinal worms 

 of mammals, these fly larvae contain an anti-enzyme which inhibits digestion, so perhaps 

 their ability to spend their lives, bathed in the digestive fluids of the pitchers, is attributable 

 to this quality as a necessary defensive character. 



Sarcophaga larvae are the largest but by no means the only pitcher-robbing insects. No 

 sooner does the cobralike hood of Chrysamphora (Darlingtonia) expand and its mouth open 

 than the first few insect captures appear in the clear fluid which fills the lower portion of 



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