DIMORPHISM. 655 



ants and bees, a distinct form so as to be readily recog- 

 nized at first sight. Among the Ccelenterates and worms 

 the forms reproducing by parthenogenesis are usually larval 

 or immature, as if they were prematurely hurried into ex- 

 istence, and their reproductive organs had been elaborated 

 in advance of other systems of organs, for the hasty, sud- 

 den production, so to speak, of large numbers of individu- 

 als like themselves. 



In insects, as we have stated elsewhere,* dimorphism is 

 intimately connected with agamic reproduction. Thus the 

 summer wingless, asexual Aphis and the perfect winged 

 autumnal Aphis may be called dimorphic forms. The per- 

 fect female may assume two forms, so much so as to be mis- 

 taken for two distinct species. Thus, an oak gall-fly {Cy- 

 nips quercus-spongifica) occurs in male and female broods in 

 the spring, while the autumnal brood of females were de- 

 scribed originally as a separate species under the name C. 

 aciculata. Walsh considered the two sets of females as di- 

 morphic forms, and that Cynips aciculata lays eggs which 

 produce G. quercus spongifica. Among butterflies, dimor- 

 phism occurs. Papilio memnon has two kinds of females, 

 one being tailless, like the tailless male, while Papilio Pam- 

 mon is polymorphic, there being three kinds of females be- 

 sides the male. 



There are also four forms of Papilio Ajax, the three 

 others being originally described as distinct species under 

 the name of P. Marcellus, P. Telamonides, and P. Walshii. 

 Our Papilio glaucus is now known to be a dark, dimorphic, 

 climatic form of the common Papilio Turnus. There are 

 dimorphic males among certain beetles, as in the Golofa 

 hastata Dejean, of Mexico, in which one set of males are 

 large and have a very large erect horn on the prothorax, 

 and in the other the body is much smaller, with a very 

 short conical horn. 



Temperature is also associated with the production of 

 polymorphic forms in the temperate regions of the earth, 

 as seen in certain butterflies, southern forms being varieties 



* Guide to the Study of Insects, sixth edition, p. 52. 



