112 BRITISH APHIDES. 



eggs, which uniformly under its influence produce 

 female forms. In other words, the drone or male bee 

 always hatches out from an unfertilised egg. At first 

 this seemed to be a grand fact to generalize upon ; 

 but shortly afterwards it was satisfactorily proved, 

 that in some other families of insects the converse 

 was true; namely, that unfertilised eggs produced 

 entire female broods to the exclusion of all males. 

 This last peculiarity is true also in the crustacean 

 Apus cancriformis. 



Yon Siebold's very important researches on the small 

 social wasps, Polistes gallica and P. diadema, must be 

 fresh in the memory of many. His observations go 

 to prove that, whilst the impregnated queen wasp 

 produces eggs, furnishing first the female and then the 

 male forms, the virgin queen can alone produce the 

 latter. He also states that the parthenogenetic pro- 

 geny of the leaf-wasp, Nematus ventricosus, is male.* 



It really would appear, that mere speciality of sex 

 has but little to do with impregnation or otherwise, 

 for the Lepidopterous genera Psyche and Selenobia 

 are stated to furnish by impregnation females exclu- 

 sively in the first case, and almost exclusively in the 

 second. 



M. H. Weijenbergh made some interesting experi- 

 ments on the same subject with reference to the un- 

 impregnated eggs of the Lepidopterous insect Liparis 

 dispar. Of the caterpillars which hatched out in the 

 following spring he destroyed all the males. The 

 imagoes appeared in August from the remaining eggs. 

 Although these were all virgins they produced eggs 

 which hatched in the next April, just like the preceding 

 batch. These unimpregnated broods appeared for 

 three consecutive years, though with diminished 

 vitality. Finally they ceased to hatch, inasmuch as 

 the eggs dried up all together. f 



* 'Beitrage but Parthenogenesis der Arthropoden,' von C. Th. von 

 Siebold. 



f 'Archives N< M rlandaises,' published by the Soc. Hollandai6e des 

 Sciences a Havleem, 1870. Also r/'</. b summary of this subject by 

 Prof. Ray Lankester, ' Nature,' October, 1872, p. ^23. 



