No. 7. — CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 

 OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 

 COLLEGE, UNDER THE DIRECTION OF E. L. MARK, No. 145. 



The Changes which occur in the Muscles of a Beetle^ Thymalus 

 marginicollis Chevr., during Metamorphosis. 



By Egbert S. Breed. 



TABLE OF CONTENTS. 



Introduction 



Part I. — Anatomy 



A. Historical Survey .... 



B. Observations 



1. Material 



2. Methods 



3. Anatomical changes of the 



muscles 



a. Metathorax 



( 1 ) . Dorsal antero-posterior 



muscles 



(2). Lateral dorso-ventral 



muscles 



(3). Ventral antero-poste- 

 rior muscles . . . 

 6. Mesothorax 



c. Prothorax 



d. Head 



e. Abdomen 



/. Appendages 



4. Discussion of results . . . 

 Part II. — Histology 



A. Historical survey .... 



B. Observations 



1. Methods 



2. Histological changes of the 



muscles 



PAGE 



317 

 318 

 318 

 319 

 319 

 321 



321 

 322 



323 



324 



336 

 337 

 338 

 338 

 338 

 339 

 339 

 340 

 340 

 347 

 347 



348 



PAQZ 



a. Muscles that pass unal- 

 tered from the larva to 

 the imago .... 

 h. Metamorphosis of larval 

 muscles into 

 (1). Muscles of the wing 



type 



o. Larval period . . . 



/3. Pupal period . . . 



y. Imaginal period . . 



(2). Muscles of the leg type 



a. Larval period . . . 



/8. Pupal period . . . 



7. Imaginal period . . 



(3). Metamorphosis of the 



intestinal muscles . . 



c. Histolysis of the larval 



muscles 361 



d. Histogenesis of the imag- 



inal muscles . . . 363 

 3. Observations on other Cole- 



optera 364 



C. Discussion of results . . . 366 



Summary 371 



Bibliography 375 



Explanation of plates 380 



349 



349 

 349 

 353 

 355 

 356 

 357 

 357 

 358 



358 



Introduction. 



While there have been numerous researches on the changes which 

 occur during the metamorphosis of insects, many points remain not 

 clearly understood, and others are in dispute. The present investigation 



VOL. XL. — NO. 7 1 



