and Position of the HymenojHera. 83 



the labium projects a little beyond the head, owing to the in- 

 creased size of the mouth -parts over those of the larva. 



At this period, the two pairs of wings are very equal in size, 

 the posterior pair but little smaller than the anterior pair, and 

 inserted much higher up the ring nearer the median tergal line 

 of the body ; and in the succeeding stage the posterior pair are 

 seen to be scarcely smaller than the anterior pair, and exactly 

 parallel in their insertions, their longitudinal diameter, and their 

 tips. This change in the position of the posterior pair of wings, 

 80 important in a morphological point of view, is accompanied 

 by a corresponding change in the proportions of the thorax. 

 The metathorax has become mostly absorbed, so as to resemble 

 more the same part in the pupa ; while the mesothorax retains 

 much of its original proportions, though becoming more com- 

 pact and presenting less of the tergal area. 



During this time the head has also greatly increased, especially 

 in the size of the appendages; the eyes, antennae, and mouth- 

 parts begin to assume the size and shape of those of the pupa. 

 Development here, as in the thorax, begins in the most impor- 

 tant central parts, and proceeds outwards to the periphery. 



In this stage (fig. 1), when the mouth-parts of the semipupa 

 have become solid enough to enable the larval head to be stripped 

 off without lacerating the extremities of the appendages, the head 

 is seen to be divided into two portions. The basal region or 

 body of the head, which is lodged under the prothorax of the 

 larva, is orbicular when seen from the front ; and its sides are 

 continuous with the sides of the thorax, as is also the vertex, 

 which is likewise of a continuous slope with that of the anterior 

 tergal portion of the thorax. Seen from the side, there is no 

 separation as yet between the head and thorax. The outline of 

 the eyes is distinct, but they are not raised above the surface of 

 the head. The antennae, clypeus, and mouth-parts collectively 

 form a second anterior portion separated by a curved line from 

 the epicranium. It is this anterior portion which lies in the 

 larval head in this stage. The great increase of size of the ap- 

 pendages of the semipupa have forced forward the hard crust 

 of the larval head, which suggested to Ratzeburg the idea that 

 the head of the pupa was originally composed of the first two 

 rings [i.e. head and prothorax) of the body of the larva*. The 

 antennae are flattened down upon the surface, resting on each 

 side of the small trapezoidal clypeus, over the front edge of 

 which they again meet, when they are flexed upon themselves, 



* " Ueber Entwicklung der fiisslosen Hymenopteren-Larven, &c." (Nova 

 Acta Natur. Curios, torn. xvi. 1832). Westwood has fully shown the fal- 

 lacy of this idea (Trans. Ent. Soc. London, vol. ii. p. 121) ; and our own 

 observations corroborate his statements and conclusions. 



