595.79 47 



V. 



Wasps and Weismann. 



THE phenomena connected with the reproduction of the social 

 Hymenoptera are of such interest, not only for their own sake 

 but also on general considerations, that the results detailed by Dr. 

 Paul Marchal in a paper entitled " La Reproduction et I'E volution 

 des Guepes Socisiles'' {Arch. Zool. Exper. etGen.,^e ser.vol. iv. pp. i-ioo, 

 1896), deserve more than cursory notice. His experiments deal with 

 various species of wasps ; and in order to give a fair presentation of 

 his theoretical conclusions, the experimental results must be briefly 

 stated. 



In terrestrial species the size of the workers increases progres- 

 sively from the beginning to the end of the season, culminating in 

 intermediate forms not much smaller than the queens, which are the 

 final product of any one complete season. Correspondingly, the 

 lower and later combs are formed of larger cells for the reception of 

 queen larvae, though of these a few may at first contain large 

 " intermediate workers" ; while the small cells contain at first workers 

 only, and later both workers and drones, the latter becoming more 

 numerous as the season advances. Contrary to the statement of 

 Reaumur, no special cells are constructed for the reception of the 

 male (drone) larvae. Combs containing both large and small cells 

 occur at times, and in such the proportion of males is unusually low. 

 The normal occurrence of fertile parthenogenetic workers producing 

 male offspring only is beyond doubt. Such workers become extremely 

 abundant if the queen is removed, or if her fecundity becomes 

 impaired ; but apparently only recently emerged imagines can attain 

 to this distinction. The determining cause of this occurrence is the 

 excess of food consumed by the workers, in consequence of the 

 absence of larvae, to whom normally they would impart a large share 

 of the food-material brought to the nest. It is fully estabhshed that 

 quantity and not quality of food is the determining factor in the 

 rearing of worker or queen wasps. 



The power of the queen to withhold spermatozoa from those eggs 

 destined to be males, and with certainty to fertilise those deposited in 

 queen cells, has been ascribed to the will. Dr. Marchal suggests a 

 new explanation as follows : — towards the end of the season the 

 spermatheca contracts with less regularity for various reasons, hence 



