312 WHEELER— ANT LARV^. 



and cylindrical and shows a further regressive development of the 

 exudatoria. Those on the meso- and metathoracic segments have 

 disappeared and the abdominal pair has short broad bases v^'ith the 

 distal portions attenuated to slender points. The labial appendages 

 have also disappeared. The mandibles are well chitinized and the 

 larva is now fed with pellets of crushed insects, like the cciJiiops 

 larva in the corresponding stage. These pellets were found in situ 

 in several of the alcoholic specimens as represented in Fig. iiB. 

 The pellet lies in the deep pocket between the head and the sternal 

 protuberance of the first abdominal segment and is therefore within 

 easy reach of the mandibles and labium of the larva. Cleared prep- 

 arations show that the salivary glands have made their appearance, 

 though they are small and slender. 



The anterior end of the fourth stage, or adult larva is shown in 

 Fig. iiC The exudatoria of the prothoracic segment now appear 

 merely as a pair of welts or folds embracing the sides of the head 

 and continuous with the more dorsal portions of their segment, 

 which is relatively smaller and less projecting than in the preceding 

 stages. The exudatoria of the first abdominal segment are still dis- 

 tinct but their distal portions are reduced to mere points, sometimes 

 absent in larvae just before pupation, and the sternal swelling is 

 much less prominent. In this stage the larva resembles that of 

 Tetraponcra throughout its various stages. In the third and fourth 

 stages of the latifrons larva, as in the corresponding stages of 

 (uthiops, the salivary glands probably furnish secretions which are 

 useful both in the extraintestinal digestion of the food pellet and as 

 substances that can be imbibed by the workers. The fact that in the 

 two species of Pachys'una the exudatoria decline pari passu with the 

 development of the salivary glands certainly suggests that both sets 

 of organs have to some extent a common function. In forms like 

 Pccdalgus and probably many other MyrmicincX, in which the de- 

 velopment of the salivary glands is more precocious, the exudatoria 

 are not developed. 



I believe, therefore, that we must interpret the exudatoria as very 

 primitive glands, but they difl:'er so nn;ch from the ordinary hypoder- 

 mal glands of insects that it will be necessary to consider them more 

 closely before proceeding further. They are, as we have seen, small 



