INSECTA. 



227 



103 



Noctua Brassicae. 



The female sexual organs {fig. 103.) consist of the ovaries (a, «), the 

 oviducts, the uterus {g), the spermatheca (6), the mucous glands (e), 

 and vagina ; but these are not all present in all insects. The external 



organs are the vulva, the sting, the 

 holders, and ovipositor, some of which 

 are likewise peculiar to particular 

 species. 



The most constant and essential 

 parts of generation of the female in- 

 sect, viz. the ovaria, are subject to 

 almost as many varieties as the testes 

 in the male ; their forms may be ar- 

 ranged into almost as many genera 

 and species, which are very often 

 analogous to those of the essential 

 glands in the opposite sex. Teh ovaria in the Lepidoptera do not, 

 however, coalesce into a single mass^ like the testes in the male : 

 they are either digitate or verticillate ; that is to say, they consist 

 of a few egg-tubes suspended to the end of the oviduct, be- 

 coming attenuated as they recede from it; or they consist of nu- 

 merous very long egg-tubes, proceeding from a short oviduct and 

 terminating in filiform extremities : they are usually disposed in 

 spiral coils bending at the two sides in opposite directions, as in the 

 Noctua BrassiccB. In the forest-fly each ovarium consists of two 

 egg-tubes ; in the flesh-fly it consists of a single tube, which is of 

 great length, and twisted spirally. In the mantis a single series of 

 short egg tubes are attached to one side of a common duct. In the 

 gnats, crickets, and locusts, the numerous egg-tubes, which are some- 

 what compressed, lie upon one another like scales, or the tiles upon a 

 roof. In the Ephemera and Stratiomys, the ovaries have the primitive 

 form of simple elongated bags in which the eggs are contained linked 

 together by delicate filaments. 



In the plant-louse (Aphis) the ovaria consist of eight short and 

 straight tubes continued from a very short and w ide oviduct : the an- 

 terior capillary beginnings of the ovarian tubes are composed of a 

 single file of nucleated cells. From these a distinct canal is con- 

 tinued for a short distance, which dilates into a sac filled with numerous 

 other nucleated cells ; a second constriction separates it from another 

 dilatation containing a more definite group of nucleated cells forming 

 a vitelline mass, presenting sometimes an elongated or larviform 

 figure ; the ovarian tube then dilates into an elongated wide receptacle 

 in which the development of the larva is completed in the apterous and 

 larviparous females, which produce their young during the spring and 



Q 2 



