322 WHEELER— ANT LARV^. 



origin of the social tendencies in the Vespidge, as we shall show in the sequel. 

 The retention of the young females in the nest, the associations between 

 isolated females, and the cooperative rearing of a great number of larvae are 

 all rationally explained, in our opinion, by the attachment of the wasps to the 

 larval secretion. The name acotrophobiosis (from oIkos, family) may be 

 given to this peculiar family symbiosis which is characterized by reciprocal 

 exchanges of nutriment between larvae and parents, and is the raison d'etre of 

 the colonies of the social wasps. The associations of the higher Vespids has, 

 in our opinion, as its first cause the trophic exploitation of the larvae by the 

 adults. This is, however, merely a particular case of the trophobiosis of 

 which the social insects, particularly the ants that cultivate aphids and 

 coccids, furnish so many examples. 



It does not seem to me that the term *' oecotrophobiosis " is aptly 

 chosen. Apart from its length, it implies, as Roubaud states, a re- 

 lationship between adult and larval members of the same colony or 

 family, comparable with that existing between ants on the one hand 

 and Aphids, Coccids, Membracids and Lycfenid larvse on the other. 

 This relationship, however, is, so far as nutrition is concerned, one- 

 sided since the ants exploit the aphids, etc., and may defend or 

 even transport them, but do not feed them. Moreover, even in 

 Belonogastcr the feeding of adults and larvae is reciprocal, and the 

 latter could not be reared if they were actually exploited to such 

 an extent as to interfere with their growth. As the relationship is 

 clearly cooperative or mutualistic, I suggest the term trophallaxis 

 (from Tp(>(f>ri, nourishment and aXXdrTav, to exchange) as less awk- 

 ward and more appropriate than " cecotrophobiosis." 



That the feeding of the young by the mother wasp without com- 

 pensation is more primitive than the condition in Belonogastcr is 

 shown by Roubaud's beautiful observations (1908, ^1910, and 

 1 91 6) on three species of Synagris in the Belgian Congo {callida, 

 slcheliana and cornuta). These wasps represent important stages 

 in the transition from the solitary to the social forms, since they 

 make earthen cells like other Eumenids, lay eggs in them and pro- 

 vide the young with paralyzed caterpillars of Hesperid butterflies. In 

 favorable seasons, when caterpillars are bundant, the behavior is like 

 that of our northern Eumenid and Odynerid wasps, numerous small 

 or single large caterpillars being placed with the egg in the cell and 

 the latter sealed up (" approvisionnement massif accelere"), but 

 when the season is less unfavorable and food scarcer, the wasp's ac- 



