OF THE HEAD OF THE IMAGO OF CHIRONOMUS. 27!) 



Fig. 2G. Labial fold or iuvagination. x 70. 



Fig. 27. Maxillary ditto. x 70. 



Fig. 28. Transverse section tlirougli the prothorax of a male larva in an advanced condition, passing 

 through the eyes and in front of the antcnnary bulbs. The longitudinal folds, /./, have lost 

 their original form as illustrated in figs. 18-20, and have become more complicated. Lettering 

 as on fig. 17, &c., with the following additions : — ^, central blood-sinus ; p.s, pupa-skin 

 surrounding the shaft of the antenna, but separated therefrom by a considerable interspace ; 

 s.d, salivary ducts, x 90. 



Fig. 29. Horizontal section through the eyes and antcnnary bulbs in a larva about to pupate, illustrating 

 a stage in the process of eversion as described on p. 27 k The small folds, /./, represent the 

 originally deep longitudinal invaginations. The eyes are drawn back behind the antcnnary 

 bulbs within, which certain newly forming nervous structures are now conspicuous, l.c, 

 larval cuticle of the prothorax. x 120. 



Fig. 30. Transverse section of the male pupal antenna showing the imaginal antenna surrounded by 

 the pupa-skiu. The part marked x is that which becomes invaginated to form the slit. 

 h, sensory hairs. x 120. 



Plate XXXI. 



Fig. 31. Transverse section through the prothorax of a male larva in an advanced condition, passing 

 through the antcnnary bulbs and the ascending ciirvature of the shaft. The antcnnary 

 nerve, a.n, of the larva is seen passing through the bulb and into the shaft, but there is 

 reason to think that it subsequently to a great extent disappears and is replaced by new 

 nervous structures within the bulb, r.f, respiratory filaments of the pupa. Other letters as 

 before, x 90. This figure should follow fig. 28 in proper sequence, but it has been 

 separated for convenience of arrangement. 



Fig. 32. Transverse section through the posterior portions of the bulbs. Lettering as before : v.p are 

 probably the minute processes on the head of the pupa seen in figs. 3 & 4, covering those 

 of the fly alluded to on p. 2G9. x 90. 



Fig. 33. Transverse section through the head of a recently emerged female ])upa, showing the last traces 

 of the folds, /./, and the facets of the eye beginning to extend themselves around the convex 

 surface of the head, x 90. 



