570 W. L. TOWER, 



Fig. 15. Transverse section through the second abdominal segments 

 of the same larva as Fig. 14 showing the position of the spiracular discs. 



Fig. 16. Fundament of an elytron in an early stage taken im- 

 mediately after the second ecdysis. 320 : 1. 



Fig. 17. Fundament of an elj'tron in the third instar about 10 

 hours later than Fig. 16. 320 : 1. 



Fig. 18. Fundament of an elytron near the end of the third instar. 

 120 : 1. 



Fig. 19. Larva in third instar to show position of the spiracles 

 and wings. 20 : 1. 



Fig. 20. 0. SCahra. Transverse section through a hind wing from 

 the same larva as Fig. 11. 70:1. 



Plate 16. 



Leptinotarsa decemlineata. 



To show development of the wings in the last larval stages. 



Fig. 21. Posterior wing of a larva at the beginning of the pre- 

 pupal period. 150: 1. 



Fig. 22. Elytron of a prepupa where rapid growth has begun. 

 From same series as Fig. 4. 320:1. 



Fig. 23. Section of an elytron in the same stage as shown in 

 Fig. 6. 120 : 1. 



Fig. 24. Section of a hind wing from same series as Fig. 28. 

 120 : 1. 



Fig. 25. Section of an elytron about twelve hours before pupation. 

 120 : 1. 



Plate 17. 



To show development of the wings during the larval stages. 



Figs. 26, 27, 28 and 29. P. variabilis, from stages in the devel- 

 opment of the elytra. 200 : 1. 



Fig. 30. JBuprestis rufipes. Section of hind wing showing mass 

 of cells about the trachea and closing the wing cavity. 



Fig. 31. Carabus sp. Elytron at the beginning of the last larval 

 stage. 150 : 1. 



Fig. 32. Leptinotarsa decemlineata. Hind wing showing posterior 

 part cut off from body wall. 70 : 1. 



Fig. 33. Orthosoma brunneum. Elytron shortly before emergence 

 of imago. 200 : 1. 



Figs. 34 and 35. Leptinotarsa decemlineata. Two stages ob- 

 served in the hypodermis where the cell contents are being re- 

 arranged. 690 : 1 . 



Fig. 36. Leptinotarsa decemlineata. Surface view of an elytron 

 showing arrangement of the compound glands, tracheae and stripes of 

 pigment. 



