224 THE BIOLOGY OF INSECTS 



colonies and nests by sending off swarms of workers with 

 one or two dozen queens." The plurality of mothers 

 C polygynous " condition) results in their nests becoming 

 crowded with " hundreds or even thousands of individuals." 

 Most of the tropical social wasps are similarly polygynous, 

 whereas the widespread Vespa (represented by seven species 

 in Great Britain) has only a single queen-foundress for each 

 nest. After surviving the winter she starts a new family 

 and habitation in the spring. Of course, a proportion of 

 the young female insects reared in one of our native wasps' 

 nests develop into queens, but the vast majority are workers. 

 It is of great interest to find that females of an intermediate 

 type may occur, smaller than a queen, larger than a worker, 

 and with ovaries reduced yet functional. O. H. Latter 

 (1904) points out that these " fertile workers " are developed 

 as the effect of an especially rich food-supply being available 

 for the grubs in certain seasons. The workers of Vespa 

 feed the grubs on fragments of captured insects, bitten up, 

 malaxated by moistening with saliva, and moulded into 

 small pellets. The wasp larvae in the chambers of the comb 

 thrust out their heads, as Wheeler remarks, " like so many 

 nesthng birds, and when very hungry may actually scratch on 

 the walls of the cells to attract the attention of their nurses." 

 It is now, however, well established that the feeding activities 

 in a wasps' nest are by no means one-sided. P. Marchal 

 (1896), C. Janet (1903), E. Roubaud (1916), and other 

 observers have found that the parent or nurse-wasps obtain 

 from the larvae which they tend sweet saliva often in large 

 quantity, and Wheeler (1923) supports the opinion that 

 this drain on the larval food supply is a potent physiological 

 factor in preventing the development of the young insect's 

 reproductive system, so that it becomes a sterile worker 

 instead of a queen. Wasps in a nest engaged in tendance 

 of the grubs stimulate the mouths of these by contact, or 

 even by seizure of their heads between their own mandibles 

 in order to incite the secretion and flow of the desired fluid. 

 In some cases at least it has been estimated " that there is 

 a flagrant disproportion between the quantity of nourishment 



