50 THE DURATION OF LIFE. [I. 



duration of life among the Cyuipidae corresponding to the con- 

 ditions under which the deposition of eggs took place ; whether 

 those species which lay many eggs, or of which the oviposition 

 is laborious and protracted, lived longer than those species 

 which lay relatively few eggs, or easily and quickly find the 

 suitable places in which to deposit them. 



Dr. Adlcr fully confirmed my suppositions and supported 

 them by the following statements : — 



'The summer generation o{ Neuroterus (SpatJipgasfer) has the 

 shortest life of all Cynipidae. Whether captured or reared from 

 the galls I have only kept them alive on an average for three to 

 four days. In this generation the work of oviposition requires 

 the shortest time and the least expenditure of energy, for the 

 eggs are simply laid on the surface of a leaf. The number of 

 eggs in the ovary is also smaller than that of other species, 

 averaging about 200. This form of Cynips can easily lay 100 

 eggs a day. 



' The summer generation of Dryophanta {Spathegaster Tas- 

 chcnbcrgi, verrucosus, etc.) lives somewhat longer ; I have kept 

 them in confinement for six to eight days. The oviposition 

 requires a considerable expenditure of time and strength, for 

 the ovipositor has to pierce the rather tough mid-rib or vein 

 of a leaf. The number of eggs in the ovary averages 300 

 to 400. 



'The summer generation o{ AudricuSy which belongs to the 

 extensive genus Aphiloirix, have also a long life. I have kept 

 the smaller Andricus (such as A. tiudus, A. cirra/us, A. noduli) 

 alive for a week, and the larger {A. itiflator, A. curvator, A. ra- 

 muli) for two weeks. The smaller species pierce the young 

 buds when quite soft, but the larger ones bore through the fully 

 grown buds protected by tough scales. The ovary of the 

 former contains 400 to 500 eggs, that of the latter over 600. 



' The agamic winter generations live much longer. The 

 species o{ Neuroicrus have the shortest life ; they live for two 

 weeks at the outside ; on the other hand, species o^ Aphilotrix 

 live quite four weeks, and DryopJianta and Biorhiza even longer. 

 I have kept DryopJuuita scukllaris alive for three months. The 

 number of eggs in these agamic Cynipidae is much larger : 

 Drynplianta and Aphilotrix contain 1200 and Ncuroterus about 

 1000.' 



