Development of the Sexes in Insects. 209 



rudiments and the definite differentiation of the sexual glands 

 appear, we have no direct investigation to show. I earnestly 

 recommend such investigation to entomologists for the solu- 

 tion of the question before us. Leuckart, however, has 

 already given an indication in this direction *, when he says, 

 " on the sixth day I find in the female larvae the first traces 

 of internal genitalia." 



With regard to the above-mentioned discovery of Meczni- 

 kow's, of the development in the embryos of the viviparous 

 Aphides of ovaries in the germ-chambers of which the forma- 

 tion of a new generation was already commenced, M, Landois 

 has informed me, by letter under date of the 6th May, that 

 he has succeeded by the gradual application of artificial cold, 

 and during the withering of their food-plants, to cause the dis- 

 appearance of the viviparous Aphides (the so-called Nurses) , 

 and the appearance in their place of the sexual generation 

 consisting of males and ovipositing females. I cannot doubt 

 this result which Landois has obtained from his experiments ; 

 but I will take the liberty of putting the question, How, in 

 this case, does the production of the two sexes simultaneously 

 with the existence of scanty nourishment agree with the new 

 theory set up by Landois ? 



From his experiments on bees, Landois draws the conclu- 

 sion that the development of female and male bees is induced, 

 independent of the fecundation or non-fecundation of the ova, 

 only by difference of the food supplied to the larvae — abun- 

 dant nourishment producing females, and scanty nourishment 

 males. According to the observations and statements of our 

 most experienced observers of bee-life, this opinion, expressed 

 by Landois as to the different feeding of the larvae of bees, is 

 not correct. All writers who have treated of the rational 

 management of bees agree in this, that the whole of the larvce 

 in the earliest period of their life (up to the sixth day) receive 

 the same nutriment ^ namely, food-paste (digested chyle-paste), 

 with which the larvae destined to become queens are fed, abun- 

 dantly and uninterruptedly, until their change to the pupa 

 state ; whilst the larvce of the worhers and drones afterwards 

 (from the sixth day) receive, instead of chyle-paste, a coarser 

 sort of food prepared from undigested honey and pollen f. 



* Bienenzeitung, 1865, p. 210. 



t To indicate only a few of the many authorities who have expressed 

 themselves concordautly as above with regard to the feeding of the larvaa 

 of bees, I cite the following : — 



Leuckart : " Ueber die N ahrung der Bienen im ausgebildeten Zustande 

 und wahrend des Larvenlebens," Bienenzeitung, 1855, p. 207. 



Berlepsch : * Die Biene und die Bienenzucht,' 1860, p. 102. 



Klein : ' Die Biene und ihre Zucht,' 1864, p. 29. 



