J >^ X \^ i J. ±^ . 



[iNoveniDer— uecemoer i>(go- 



same species, and this ought to furnish 

 a most important character in the separ- 

 ation of species. The system is alike 

 in no two species hitherto examined by 

 me, though this may not hold good 

 throughout the family. 



Another very important point struck 

 me. In none of the wingless forms 

 does the poriferous system attain the 

 complexity found in the winged forms. 

 From the young louse just born, to the 

 pupa, the poriferous system remains 

 the same, and is very similar in all the 

 species ; but when the winged form is 

 assumed, the specific poriferous system 

 makes its appearance. It is well to say 

 here, that I have not examined the true 

 sexes and can say nothing of any spe- 

 cies in the sexually perfect condition. 

 In all the wingless viviparous females 

 examined, the larval poriferous system 

 was retained, and J conchide therefore 

 that ive have to do, really, with a true 

 reproduction among larval fortns, 

 and that wingless viviparous fetnales 

 among aphididae are not mature in- 

 sects i7i any sense oj" the term: hut 

 that they represent simply an arrested 

 larval stage, -which under other con- 

 ditions would develop into a winged 

 form. The winged viviparous females 

 are ultimate or mature forms in which 

 both sexual elements are represented in 

 the form of the original germ cell, 

 which by budding, develops the embryo 

 brought forth. It seems rather elemen- 

 tary, but equally necessary to explain, 

 that the term '"budding" as used in 

 reference to this method of reproduc- 

 tion, is a budding of the germ cell, and 

 not a budding from the body of the in- 



sect ; but in this latter sense I find that 

 the term is quite generally understood. 



With these, preliminary, observations 

 and conclusions, I will proceed to 

 details. 



In all the aphides examined the first or 

 basal joint is subglobose, stout and short ; 

 the second is also short, but scarcely glo- 

 bose ; the third is the first of the long 

 joints and it is longer than either tiie 4th 

 or 5th, which are subequal in length, 

 and sometimes is as long as both to- 

 gether. The sixth, or terminal, is what 

 I have termed the whip joint. It en- 

 larges gradually from the base for a 

 short distance and is then rather 

 abruptly narrowed from one side, giv- 

 ing a false appearance of segmentation. 

 From this point it continues to the tip, 

 gradually tapering to a point. It is 

 flexible, and the resemblance to a whip 

 is not fanciful. 



