THE DEVELOPMENT OF ANTS. 



77 



on to the semipupa stage, but in certain ants (Ponerinae and most Cam- 

 ponotina? ) it first spins a cocoon (Figs. ^5 and 46). Except for this 

 episode, the development of all ants is essentially the same. The 

 mature larvae of cocoon-spinning species have to be buried in the 

 earth by the workers or covered with particles of detritus, since the 

 larva cannot spin an elliptical envelope about itself while it lies freely 

 in the nest, but must lie in a cavity so that it can fix the threads from 

 its sericterics to different points in an adjoining wall. The larva 

 moves its head back and forth and lines the cavity in which it lies 

 with a fine web of silk. As soon as this has been accomplished it is 

 unearthed by the workers and the foreign particles adhering to the 

 outer surface of the cocoon are carefully removed. The cocoon is 

 now found to contain a semipupa (Figs. 47, a, and 49), which resem- 

 bles the larva except that the 

 body has become straight and 

 rigid, with its anterior end no 

 longer bent in an are and with 

 a pronounced constriction be- 

 hind the cpinotal segment. 

 Ueneath the cuticle the legs, 

 wings and cephalic appen- 

 dages, which have developed 

 in the meantime from the his- 

 toblasts, are clearly discern- 

 ible, though still of small size, 

 more or less folded and closely 

 applied to one another and to 

 the surface of the body. The 

 larval skin is soon ruptured along the back (Fig. 47, >), stripped 

 from the body and pushed into the caudal pole of the cocoon. 

 The small intestine has meanwhile formed an open communication 

 with the chylific stomach and the mass of meconium and peri- 

 trophic . membranes is voided through the large intestine and also 

 deposited in the posterior pole where it forms a black or dark brown 

 spot. In the meantime the appendages have been growing rap- 

 idly and assuming their adult structure, though they are still bent and 

 closely applied to the body (Fig. 47, r). The further external changes 

 in the quiescent pupa, which is now definitely formed, consist in a 

 gradual deposition of pigment. This makes its appearance first in 

 the eyes, which become intensely black before the color spreads over 

 the remainder of the body ( Fig. 49). Finally, when all the organs have 

 reached their full development, the workers cut open the antero-ventral 



FIG. 43. Larva of Phcidole instabilis. 

 (Original.) a. Young larva: b. bifurcated 

 hair of same : c . adult larva ; d, dorsal spring- 

 like hair of same. 



