OF THE HEAD OF THE IMAGO OF CHIEONOMUS. 277 



EXPLANATION OF THE PLATES. 

 Plate XXVIII. 



Kg. 1. Half-grown larva. The numerals iiidieate the numbers of the iMxly-scgments. p-app, pro- 

 thoracic, and a.app, anal appendages ; r.t, respiratory tubules ; a.p, anal processes, y 10. 



Fig. 2. Full-grown larva. Letters and numerals as before, r.f, respiratory filaments of the pupa ; 

 /, leg of fly ; w, wing. All seen through the transparent cuticle. x 10. 



Fig. 3. ]\Iale pupa, front view. ?•./, respiratory filaments. x 10. 



Fig. 4. Ditto, in profile. ««/', antenna; r./>, processes on vertex. x 10. 



Fig. 5. :\Iale fly. x 10. 



Fig. 6. Female fly. x 10. 



Fig. 7. Head of larva, dij, clypeus, the diverging margins of which are strongly marked, inasmuch as 

 they indicate the course of the longitudinal invaginations or folds which lie l)cncath them ; 

 Ir, labrum ; ant, antenna ; md, mandible ; o, eye-spots, x 70. 



Fig. 8. Ventral surface of ditto, mx.p, maxillary palp ; x, square marking on ventral surface of labrum ; 

 sm, submeutum ; ;/, striated flap flanking the submentum. x 70. 



Fig. 9. Front or anterior view of ditto, showing the position of the mandibles at right angles to each 

 other; letters as before, x 90. 



Fig. 10. The mentum. x 300. 



Fig. 11. Antenna of male fly : x 30. 11a. Portion of the shaft : x 150. \\h. Diagrammatic section 

 of the same : x 150. 



Fig. 12. Antenna of female fly. x 30. 



Fig. 13. One of the striated plates flanking the submcntum. x 300. (For convenience of arrangement 

 this has been placed in a vertical position.) 



Plate XXIX. 



Fig. 14. Head of the male fly. The antennaj are removed with the exception of the bulbous basal 

 joints b, in the centre of each of which is a hollow with radiate markings whence the shaft 

 has been taken out. v.p, processes on the vertex ; s, transvei'se suture ; or, orifice of 

 chitinous cephalic cavity ; e, epistome; /?•, labrum ; /, labella ; /«,r.jo, maxillary palp, x GO. 

 14a. Extremity of labrum : x 300. Wh. Extremity of lingua : x 300. 1 1- f. One of the 

 processes on the vertex : x 300. 



Fig. 15. Section showing one of the chitinous cephalic cavities, ex. e, epistome ; /, labella; b, bulb of 

 antenna. x 100. 



Fig. 16. Dissection showing the cephalic cavities, c.c, in front view, attached behind the epistome. x 90. 

 16 a. Posterior extremity of one of the cavities showing the slit-like opening, x 90. 



Fig. 17. Diagram showing the newly forming epidermis within the head and thorax of a larva in the 

 last period of larval life, as it would be revealed by the removal of the cuticle which is still 

 indicated in outline at I.e. Below the orifice, t.f, of the transverse fold, the external 

 epidermis of the ])rothorax has been further removed, revealing the upper wall, /./', of 

 the fold (compare t.f, figs. 19, 2U, 24, & 25), the cut margin of the removed epidermis 

 being indicated by the jagged line m ; the nerve-centres and the oesophagus are also 

 seen. I.e, larval cuticle ; ant, larval antenna ; a.n, nerve of the antenna, around which the 

 imaginal antenna is in course of formation ; /./, longitudinal folds ; ep, surface of the 

 exposed epidermis ; /./, orifice or cavity of transverse fold ; /./', us upper wall exposed ; 

 m, cut margin of epidermis; o, extremities of the longitudinal folds seen beneath the 



