130 BEITISH APHIDES. 



giving sexuated forms, whilst the aerial PemphigincB 

 (P. bursarius, P. affinis, &c.) lay what I have called 

 " oeufs bourgeons," giving agamous insects with rostra, 

 and having to change their skins four times before 

 laying eggs (oeufs bourgeons?). This leads me to 

 believe that the underground insects are only a form 

 of the aerial ones, and the principal as being the 

 sexuated." 



Again, in a communication more recently made to 

 the Academy of Science of Montpellier, he details some 

 experiments made to prove the identity of Pemjpliigus 

 jilaginis with Pemphigus bursarius. Experimentally 

 he bred " thousands " of the former under a bell 

 glass containing a living plant of Gnaphalium pre- 

 sumably free from P. filaginis, on which he purposely 

 had placed specimens of P. bursarius. Subsequently, 

 he has expressed his intention to hatch some eggs of 

 P. filaginis, — which are exceedingly plentiful at Mont- 

 pellier, to see if they will produce the "fundatrice" of 

 P. bursarius. This experiment is the more necessary 

 since it is exceedingly difficult to eliminate all germs of 

 P.filaginis from such a woolly plant as Gnaphalium. 



Shortly expressed, M. Lichtenstein thinks it probable 

 at least, that the aerial Pemjjhigince are dimorphic like 

 Phylloxera. That the winged forms produce two kinds 

 of agamous insects, one of which undergoes several 

 moultings, and then produces the ordinary aerial males 

 and females : the other agamous insect descends into 

 the ground, and, after taking some such form as Pe^n- 

 phigus Boyeriy produces " pupse '^ which do not moult. 

 These finally give birth to the mouthless but other- 

 wise perfect sexes as above. 



Proofs are yet wanting, but Entomologists have 

 much to hope from the perseverence and industry of 

 M. Lichtenstein. 



