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 Mefenthes, 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 (Sarcophaga Sarraceni@), own cousin to 
the speckled nuisance (S. carnarza) 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 larve 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 
