136 HEMIPTERA. 



tube in the wingless female, Fig. 82, is chitinous at 

 its extremity. The legs are similar in structure. 

 The abdomen in both forms bears 

 two tubes, from which the sweet 

 liquid, or "honey-dew," exudes. Ants 

 feed upon these sweet excretions, and 

 p. g^ have also learned to keep the Aphides 



and to take care of them in their nests.^ 

 The plant-lice are good illustrations of that process 

 of reproduction known as parthenogenesis, or the pro- 

 duction of living forms without the intervention of the 

 male. The sexually perfect males and females are 

 born usually in the autumn. After pairing, the males 

 die, but the females do not die until they have laid 

 their eggs. In the spring these eggs, which are often 

 spoken of as true ova because they are fertilized, 

 hatch ; but the offspring are usually wingless females 

 which are able to feed immediately after birth. These 

 females are not sexually perfect in structure, and have 

 therefore been called " agamic." They do not pro- 

 duce true eggs, but in many cases they are vivipa- 

 rous, or, in other words, bring forth living young, which 

 feed on the milk excreted by the parent until strong 

 enough to pierce the bark or leaves and suck the 

 juices of the plant on which they live. This genera- 

 tion is either wingless or winged or both, but the 

 number of winged forms is limited ; they are agamic 

 individuals which can migrate and found other colo- 

 nies. Besides these viviparous forms, there may be 

 agamic individuals in the same colony which pro- 

 duce egg-like bodies (pseudova), from which the 



1 For fi^ther remarks, see p. 240 of this Guide. 



