and Position of the Hymenoptera. 87 
of the internal organs, which is simply a continuation of the 
outer tegument, or arthroderm, is, in the process of moulting, 
sloughed off with that outer tegument*. 
Whereas before the head and thorax together were but little 
more than one-half as large as the abdomen, now they are con- 
jointly nearly equal in size to the abdomen (fig. 3). The greatest 
changes have gone on in the two anterior regions of the body, 
They unitedly tend to assume a spherical form, while the elon- 
gated abdomen is shortened and very perceptibly altered in form, 
approaching near that of the pupa, and the whole body is 
flexed more upon itself. 
The head is still closely appressed to the prothorax, but much 
less so than formerly, since the increasing size and different 
proportions of the prothorax have pushed it away. This act of 
separation has effected an important change in the position of 
the head as related to that of the rest of the body. It is now 
truly vertical. Before, its greater length was more continuous 
with the longitudinal axis of the body, that is, nearly horizontal, 
or rather inclined at a slight angle from the longer axis. The 
horizontal position is normal in the lowest insects, as the Neu- 
roptera. In the Hymenoptera the longer axis of the head is 
most completely vertical. 
The head in its size, and the development of the appendages, 
including the mouth-parts, now begins to resemble those parts 
in the pupa. The eyes are larger and more distinct than before; 
the maxille and antenne, though still very short, are shaped 
more like those parts in the pupa. In the antenne, the most 
marked change takes place in the three basal joints, or the 
“scape,” of which the second joint now becomes the longest 
and somewhat contracted in the middle and round at the extre- 
mity ; while the terminal joints are still doubled upon them- 
selves, and rest folded upon the mouth-parts. 
The thorax also resembles that of the pupa, though longer ; 
and the basal ring of the abdomen (propodeum) is still exposed 
to view when seen from above. At this stage the preescutum 
of the mesothorax, before very distinct, is no longer seen, as in 
the pupa it is mostly absorbed and passes out of sight, though 
in the Tenthredinide it is a large and conspicuous portion of 
the mesonotum. 
Most interesting changes have occurred in the hinder part of 
the thorax. Whereas in the previous stage the mesoscutellum 
was immersed in the ring to which it belongs, it is now elevated 
and becomes very prominent ; the thorax posteriorly falls rapidly 
* It remains yet to be proved whether the biliary tubes, salivary glands, 
and inner genital glands and cavities form exceptions to this rule. 
