THE HOME OF THE BEES. 601 
alis, as seen lying in its cell. The limbs are folded 
close to the body in the most compact way possible. 
On the head of the semi-pupa, 7. e. a 
transition state between the larva and 
pupa, there are two prominent tubercles 
situated behind the simple eyes, or ocelli ; 
these are deciduous organs, apparently reo | 
aiding the insect in moving about its 
cell. They disappear in the mature 
pupa. 
To those accustomed to rearing butter- 
flies, and seeing the chrysalis at once 
assuming its perfected shape, after the cat- pig.. | € 
erpillar skin is thrown off, it may seem 
_ strange to hear one speak of a “half-pupa,” 
and of stages intermediate between the 
larva and pupa. But as we have before 
stated on page 429, the external changes 
of form, though rapidly passed through, 
consisting apparently of a mere sloughing 
off of the outer skin, are yet preceded 
_ by slow and very gradual alterations of "ina ents tate. 
tissues, resulting from the growth oftis i Fupi of Say 
cells.* An inner layer of the larva-skin ais oo 
separates from the outer, and, by changes reratetus. 
in the ‘form of the muscles, is drawn into different posi- 
tions, such as is assumed by the pupa, which thus lies 
concealed beneath the larva-skin. But a slight alteration 
is made in the general form of the larva, consisting most 
of an enlargement of the thoracic segments, which is often 
overlooked, even by the special student, though of great 
Fig. 4. 
i ld 
*On 429, line 5, we say, “the changes though rapid are gradual.” Tt shou 
toad; the Changte tE e DANI widdlting®) aE though the steps that lead to 
them are gradual. 
AMERICAN NAT., VOL. I. 76 
