2l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



importance in the insect communities of the practice of trophallaxis, 

 or mutual exchange of food (among the Vespidae the larvae give up 

 the secretion of their labial glands to the nurses), and also the exist- 

 ence among the Vespidae of naked or gymnodomous nests (that is, 

 with combs not protected by envelopes) and calyptodomous nests 

 (those having the envelopes). 



In the larvae of the Polistini (of Polistcs Latr.), which form primi- 

 tive communities and live in gymnodomous nests, the ist urite not 

 only is longer than the two following urites, but projects on the ven- 

 tral surface like a moderately developed hump ("trophothylax," 

 sensu Wheeler), The considerably pigmented cranial integument is 

 well provided with rather long hairs, and the very remarkable maxillo- 

 labial complex is almost as wide as the head capsule, which conspicu- 

 ously projects on the ventral face of the body (owing to the great 

 development of the postlabium) and has also a pigmented integument. 

 The larvae of the Vespini (for instance Vcspnla Thorns., Dolichovcs- 

 pnla Rohw., and others), which live in more highly evolved com- 

 munities and in calyptodomous nests, have the 2d traylike urite 

 remarkably projecting on the under side ("tropholopade," sensu 

 Grandi), the cranial integument not pigmented, its cuticle provided 

 with a small number of microscopic hairs, and the maxillolabial com- 

 plex kept within moderate limits (owing also to the shortness of the 

 postlabium) and not pigmented (palpi excluded). In both, the so- 

 called "spinneret" (an external organ placed anteriorly in the labium, 

 where it is joined to the prepharynx, and at the tip of which the duct 

 of the salivary or labial glands opens), which in the solitary Vespidae 

 has the shape of a small transverse, more or less sclerotized lamina, 

 looks like a double membranous lip which is more or less distinctly 

 trilobate and rich in filiform tegumental outgrowths. "Trophothylax" 

 and "tropholopade" serve as a support for the alimentary bolus which, 

 sticky as it is, adheres to it even though the comb openings are turned 

 downward and therefore the larva is downheaded. 



The spinneret structure seems to be well suited to the trophallactic 

 function. Finally the head of the Polistini is seemingly modified to 

 form a kind of cover for the comb cell, in correlation with the fact 

 that in the nest not covered by protective envelopes the larva is in 

 direct contact with the external environment. 



The honey-bee communities are considered to be among the highest 

 insect colonies. They present such an advanced way of nursing their 

 offspring that larvae are not compelled to take care of themselves or 

 to make any effort to take food. Now, these larvae, as far as is 

 known, are the only larvae of Hymenoptera Aculeata exhibiting (ac- 



