SOME EARLIER OBSERVATIONS ON NATURAL PAR- 

 THENOGENESIS IN INSECTS 



Long before the importance of the spermatozoon in fertili- 

 zation was fully recognized, Reaumur, Bonnet, and a number 

 of other eighteenth-century authors had established the fact 

 that plant lice bring forth living young without previously 

 pairing. Kirby 1 found that under ordinary conditions of tem- 

 perature and moisture, the parthenogenetic generations of 

 aphides can follow one another for four years (possibly in- 

 definitely) without as a rule giving rise to males. Only under 

 special conditions do plant lice produce both sexes, which then 

 pair. This pairing leads to the laying of eggs from which 

 hatch, without exception, parthenogenetic females that give 

 birth to living young. 



These observations led entomologists to search for further 

 cases of parthenogenesis. It was soon discovered that certain 

 butterflies, belonging to the genus Solenobia, lay unfertilized 

 eggs 2 which develop eventually in a thoroughly normal manner 

 into butterflies. Von Siebold, who repeated and confirmed 

 these investigations, also found parthenogenetic reproduction 

 in another butterfly, Psyche helix, 3 of which the males were 

 quite unknown at that time. In all these cases not only were 

 the larvae arising from the unfertilized eggs normal, but they 

 also developed into perfectly normal sexually mature insects. 



But the greatest sensation was aroused by the observations 

 of Dzierzon on parthenogenesis in bees. 4 He was led to the 



1 Quoted after Ratzeburg, Die Forstinsekten, Part III, 1844. 



2 We gather from von Siebold's monograph that these facts were first dis- 

 covered by DeGeer. 



3 Von Siebold, Wahre Parthenogenese bei Schmetterlingen und Bienen, Leipzig, 

 1856. 



< According to von Siebold, Dzierzon first published his observations and con- 

 clusions in the year 1845 (in the Eichstadter Bienenzeitung). 



43 



