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, 
“fon the sixth day I find in the female larve 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. J 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 larvee of bees, is 
not correct. All writers who have treated of the rational 
management of bees agree in this, that the whole of the larve 
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 larvee destined to become queens are fed, abun- 
dantly and uninterruptedly, until their change to the pupa 
state; whilst the larve of the workers and drones afterwards 
(from the sixth day) receive, instead of chyle-paste, a coarser 
sort of food prepared from undigested honey and pollenf. 
* Bienenzeitung, 1865, p. 210. 
+ To indicate only a few of the many authorities who have expressed 
themselves concordantly as above with regard to the feeding of the larvze 
of bees, I cite the following :— 
Leuckart : ‘“ Ueber die Nahrung der Bienen im ausgebildeten Zustande 
und wihrend des Larvenlebens,” Bienenzeitung, 1855, p. 207. 
Berlepsch : Die Biene und die Bienenzucht,’ 1860, p. 102. 
Klein: ‘ Die Biene und ihre Zucht,’ 1864, p. 29. 
