72 ASSOCIATION OF ORGANISMS THE WEB OF LIFE 



fluid which fills the lower part of its prison. The unfortunate 

 victims are not digested, as in Nepenthes, but either drown or 

 starve, after which their bodies decompose to form a sort of 

 liquid manure, parts of which are no doubt absorbed as food. 

 Yet, strange to say, a few flies, and a small moth, regularly lay 

 their eggs in the decomposing mass contained in these pitchers, 

 and possess climbing-irons, so to speak, which enable them to 

 get out again with the greatest ease. One such form is a 

 species of Blow-Fly (Sarcopkaga Sarraceni<z\ own cousin to 

 the speckled nuisance (S. carnaria) that lays her eggs in our 

 meat, and to which we give the same name. Each foot of this 

 fly is possessed of a long and sharp claw, which can be pushed 

 between the scales of the pitcher, and firmly fixed into the under- 

 lying tissue. The maggots which hatch out of her eggs feed on 

 the putrefying substances surrounding them until they are full 

 grown, when they easily get out of the pitcher, not by climbing, 

 which would be impossible in their case, but by the simple device 

 of eating a hole in the wall. Once outside, they enter the ground, 

 and there pass into the motionless pupa stage, from which the adult 

 fly later on emerges. The small moth (Xanthoptera semicrocea) 

 for which the Sarracenia pitchers have no terrors is adapted for 

 climbing in much the same way as the Blow- Fly. For each of 

 the second legs possesses a pair of long sharp spines at the end 

 of its shin (tibia), while two pairs of such spines are similarly 

 situated on each of the hind-legs. The caterpillars do not, like 

 the fly-maggots, eat their way out of the pitcher, but climb out, 

 though in quite a different way from their mother. Their solution 

 of the problem is equally effective, for they spin a web of silken 

 threads over the slippery scales, and thus secure the necessary 

 foothold. 



All the carnivorous forms so far mentioned, though they 

 live in marshy places, are land plants, more or less perfectly 

 adapted for the capture of insects and other small terrestrial 

 animals. Some of them, however, have aquatic relatives, which 

 are to be found floating in ditches and ponds, where they prey 

 chiefly upon small crustaceans, such as water-fleas, mussel-shrimps, 

 and copepods, though the larvae of gnats and other insects are also 

 among their victims, besides which they catch large numbers of 

 the minute motile plants known as Diatoms. The floating habit 

 conduces to success in this matter, for small crustaceans, &c., are 



