52 PHIL RAU AND NELLIE RAU 



antennae and mouth-parts, and yet were dead in their cells, 

 some of them still in their cocoons ; others were out of the cocoon 

 but had died before biting their way out of the cell or even 

 while doing so. In this stage we find the mortality to be 130, 

 or 3 per cent of the total. 



Elimination within individual families 



We have found that a certain per cent, of the cells that are 

 built cannot possibly bring forth adults. In some cases the 

 defect is the fault of the mother in not having properly filled 

 the cell, or having forgotten to lay the egg, etc. In other cases 

 no adults can be expected to emerge, but through no fault of 

 the mother, as for instance, where the young are destroyed by 

 parasites. However, there is in each nest or colony a portion 

 of the cells which contain all the rudiments for producing a 

 new generation, but the organism may or may not have the 

 inherent vitality to press on to the completion of its develop- 

 ment. For want of a better name we shall be obliged to refer 

 to these throughout the succeeding paragraphs as the potentially 

 productive cells or the potentially emergable young wasps. 



There were in this collection 1,701 such cells, or 39 per cent, 

 of all built by these mothers. Even among these which were 

 apparently unhampered by any obstacles to their growth and 

 were supplied with all things required for their development 

 to adulthood, we find heavy elimination in different stages. 

 This loss of life is due largely, I presume, to inherent weakness, 

 or if not inherent weakness, to what might be called the inability 

 of some individuals to resist extreme conditions which only 

 the most vigorous individuals can survive. It is a startling 

 discovery that in this population, barely one out of ten of even 

 these apparently perfectly equipped young ever lived to see 

 the light of day. 



When we examine certain nests we find the potentially good 

 organisms eliminated in some colonies in many different stages 

 of their development; in other nests it is clear that these un- 

 molested and promising young have all dropped off at the same 

 stage of their development, although not at the same time of 

 the calendar, from which we may infer that their death cannot 

 be attributed to some environmental catastrophe, but to some 

 cause within themselves. 



