REPRODUCTIVE ORGANS. 



637 



It being impossible to become an insect, it is also impossible to 

 know what an insect feels and appreciates. It is more than pro- 

 bable that insects have sense organs which have no counterparts 

 amongst vertebrate animals and these we cannot even hope to in- 

 vestigate. It is further practically certain that the range of eyes, 

 ears and other sense-organs differs from that of the corresponding 

 sense-organs in man. Insects probably hear sounds we cannot 

 hear and see things hidden from our eyes, but the difficulty of 

 research in this direction is 

 great and at present we are 

 in a state of very consider- 

 able ignorance as to their 

 powers of sensation. 



Reproductive Organs. In- 

 sects are bisexual, but occa- 

 sionally parthenogenetic. 

 Both ovaries and testes are 

 confined to the abdomen 

 and as a rule to the pos- 

 terior part of it. In a few 

 cases, as in the Thysanura, 

 the ovarian tubules are seg- 

 mentally arranged though 

 united by a common ovi- 

 duct on each bide, and 

 stretch throughout the ab- 

 domen. In the great major- 

 ity of cases the external 

 orifice is situate between the 

 eighth and ninth segments, 

 but it may be one segment 

 in front, or one segment behind this level. 



The organs are paired and as a rule there are several ovarian 

 tubules ; in the queen termite some fifteen hundred, in the 

 queen bee some hundred, but usually six or eight occur on each 

 side of the body (Fig. 396). Within these the ova are formed 

 and the tubules on each side unite into an oviduct. Primitively 

 the right and left oviduct opened independently, a condition of 

 things which still obtains in the Ephemeridae and in Lepisma, 

 but in other insects the two oviducts unite into a common, 



FIG. 396. Female sexual organs of Vanessa 

 iirticae (after Stein). Ov the ovarian tubes 

 cut off ; Re receptaculum seminis and acces- 

 sory glands ; Va vagina ; Re bursa copulatrix 

 with duct leading to the oviduct ; Dr glandular 

 appendage ; Df glandulae sebaceae ; R 

 rectum. 



