Bbebd. — Muscle Metamorphosis. 



PLATE 6. 



Fig. 13. Posterior face of lateral (right) portion o- cross section of the meta- 

 thorax of an imago showing tiie parts affected by the contraction of 

 musculus ei)isternalis [esln.). X loO. 



Fig. 14. Cross section of the largest fibre of musculus metanoti. Drawn from a 

 resting larva about midway in its development. X 800. 



Fig. 15. Cross section of that portion of musculus metanoti which has been de- 

 rived from the largest fibre of this muscle in the larva. Drawn from 

 an imago. Compare Fig. 14. X 800. 



Fig. 16. Cross section of a functional larval muscle fibre. Feeding larva. X 800. 



Fig. 17. Longitudinal section of a fibre of retractor mesothoracis inferior. Drawn 

 from an imago. X 1600. 



Fig. 18. Cross section of a fibre of fle.xor alae metathoracis secundus drawn from 

 tlie same series of sections. X 1600, 



Fig. 19. Cross section of flexor coxae metathoracis secundus. Drawn from a 

 young jmpa. X 800. 



Fig. 20. Cross section of a circular muscle fibre of the foreintestine of an imar/o. 

 X 1600. 



Fig. 21. Cross section of three fibres of flexor coxae metathoracis secundus. 

 Taken from an old pupa. Compare Fig. 19. X 800. 



Fig. 22. Cross section of a functional larval muscle fibre. Feeding larva. X 800. 



Figs. 23-32. Of these figures, Figs. 23-25, 30 and 31 form a series of longitudinal 

 sections, and Figs. 26-29 and 32 a series of cross sections, of small por- 

 tions of muscle fibres of the wing type. These drawings illustrate the 

 changes in the finer structure of these muscles during tlieir metamor- 

 phosis. All of tlie figures are magnified 1600 diameters. 



Fig. 23. Feeding larva. ■ Longitudinal section of part of a functional fibre. 



Fig. 24. Resting larva. Longitudinal section of part of musculus metanoti. 



Fig. 25. Resting larva a few hours before pupation. Longitudinal section of part 

 of musculus lateralis metathoracis anterior. 



Fig. 26. Feeding larva. Cross section of part of a functional fibre. 



Fig. 27. Resting larva. Cross section of part of flexor coxae metathoracis 

 secundus. 



Fig. 23. Resting larva a few hours before pupation. Cross section of part of mus- 

 culus metanoti. 



Fig. 29. Midway pupa. Cross section of part of musculus lateralis metathoracis 

 posterior. 



Fig. 30. Midway pupa. Longitudinal section of part of musculus metanoti. 



Fig. 31. Young imago. Longitudinal section of part of musculus metanoti. 



Fig. 32. Old pupa. Cross section of part of extensor alae metathoracis. 



