102 MISS EMBLETO^S" ON CERATAPHIS LATAlSTIiE. 



fact that no males * have been found, yet in the colonies there 

 are always young forms: thus the reproduction as carried on in 

 this country must be solely parthenogenetic, and since the 

 creature is not in the true imago condition, it is a sort of 

 paedogenesis as well as parthenogenesis. Possibly this condition 

 results from the fact that the creatures live in hothouses where 

 tlie climatic conditions are constant and the food- supply 

 uniform, whereas in a state of nature one or both of these 

 factors might be varied. IE these natural conditions could be 

 imitated, we should perliaps succeed in getting other generations 

 to follow on this aleurodiform stage. In the case of Sormaphis 

 Jiammnelidis, the generation which leaves the gall does so on 

 account of the food becoming used up. The Ceratapliis on 

 orchids in our greenhouses does not experience this, for the food- 

 supply is fairly constant, and also the atmospheric environment : 

 thus it seems probable there is no incentive to produce the 

 ' winged form. 



Our insect, therefore, is seen to exhibit the simple condition 

 of life-cycles as described by Dr. Sharp, while its ontogenetic 

 and morphological form is that which occurs as part of the 

 complex series of generations so lucidly depicted by Pergande. 

 These facts lead to the supposition that it is one of the 

 migratory Aphides that has been deprived of the series of meta- 

 morphoses, owing to an artificial mode of life. 



When Huxley studied Aphides, the remarkable phenomena 

 that he met with so impressed him that he devoted considerable 

 attention to their bearing on the questions of individuality and 

 the individual in Biology. Since then, the discoveries that 

 have been made in this group of Insects have rendered the 



* Signoret's suggestion that the differences he observed in the larvas may be 

 sexual, is probably incorrect, if we may judge from the life-histories of the 

 species described by Pergande. In the latter, the sexual forms are produced 

 in a special final generation, quite distinct from the preceding generations 

 of parthenogenetic individuals. The larvae that Signoret thought might be 

 males (differing from the others mainly in possessing no frontal horns) 

 occurred indiscriminately, and not in a special sexual generation, as described 

 by Pergande. It is probable that those Signoret states as being without 

 horns were merely very early larvae in which these organs were not yet fully 

 developed ; I have often found in very young individuals that the horns are 

 almost undisceruible. 



