Chapter II — 37 — Sarracenia 



Eventually only a single larva occupies a pitcher. The wide separa- 

 tion of pitchers of 5. jlava, rubra, Drummondii, Sledgei and minor are 

 a practical hindrance to such movements of very young larvae from 

 one pitcher to the other, and it is in these that the other species of 

 £^>'m lay their eggs singly. "Thus," says F. M. Jones, "the habit 

 of growth of the food plant determines the egg-laying habit of the 

 associated insect" (1921). 



The newly hatched larva is very small (2.6 mm.), and being trans- 

 lucent and half buried in the tissues on which it feeds and partly 

 covered by debris enclosed within the tube, seems pretty well pro- 

 tected without further ado. E. Ridingsii on hatching retires to the 

 grooves in the hd-stalk of S. flava, and there forms for itself a small 

 tent of silk and frass, on the floor of which it continues feeding. The 

 older larvae of all three species make use of a method of isolating 

 themselves from the outside world as follows. They spin a diaphragm 

 of silk webbing across the mouth of the tube, either transversely or 

 more or less obliquely according to the position of the hd, and in 

 5*. psittacina, across the mouth of the entrance tube. Any accidental 

 openings are closed by webbing, and thus they immure themselves 

 in a food chamber from which rain is prevented entrance. Larvae 

 of a spring brood, when they find themselves in young tender pitchers, 

 use another quite extraordinary method of insuring for themselves a 

 safe retreat. The young larva then eats away a ringing groove near 

 the top of the pitcher. Above this the pitcher wall dies, dries, and 

 becomes indurated, sagging over and barring the entrance. In the 

 chamber thus formed the larva feeds and hibernates. In the pitchers 

 of S. flava, which die down during the winter, the larva retires to the 

 lower regions of the pitcher, and there ensconces itself in a chamber 

 plugged by webbing and frass, where it awaits the spring. A curious 

 variant of this habit is displayed by the caterpillar of Exyra Ridingsii, 

 which before pupation prepares for the future by cutting an emergence 

 hole above its point of pupation, so that the moth may easily escape, 

 and below a small hole for the drainage of water, so that its pupation 

 chamber may not be flooded. It then forms its chamber by webbing 

 spun loosely so as to allow water to pass, and then spins its cocoon 

 of webbing and frass. Exyra semicrocea, when it pupates in the pitchers 

 of S. psittacina, handles its situation somewhat similarly, but with 

 special attention to the peculiarities of the host plant. Usually when 

 the larva intends to pupate it passes into an uninjured pitcher. Since 

 that of 5". psittacina has a lobster-trap entrance, out of which escape 

 would be difficult — not because of the size of the opening, but be- 

 cause of its re-entrant character — the larva first cuts an escape hole 

 in the roof region of the hood. 



After hibernation the larvae (the third instar), are voracious, and, 

 emerging in the spring, attack not only the pitcher, but the flowers 

 and young fruit which they devour. When ready to pupate the larva 

 cuts a hole in a young growing leaf still unopen, ascends the tube, 

 and feeds on the inner tissues. This causes the tops of the pitchers 

 to wither and the dead portion to topple over. E. Rolandiana does 

 the same in S. purpurea. The larvae of these moths have lateral 

 tubercles or "lappets" which, according to Jones, prevent them from 



