IV WEST VIRGINIA EXPERIMENT STATION. 



new trouble threatened by the swarms, 366, Trees attacked by 

 other bark beetles did not die, 367. The trouble ended, 367. 



CONCLUSIONS, ....... 367 



Cause of the trouble, 367. When the destructive bark beetle dis- 

 appeared the timber quit dying, 367. Further trouble prevented, 

 368. 



AREA INVADED BY THE DESTRUCTIVE PINE BARK BEETLE, . 368 



Two KEMARKABLE FEATURES OF THE INVASION, , . 369 



ON THE CAUSES OF THE UNIVERSAL DEATH CF THE INSECT, . 370 



Climatic Conditions, 370. Table of Temperatures Dec., 1892, and 

 Jan., 1893, 371. Insect Diseases, 374. Parasitic and Predaceous 

 Enemies, 378. Conclusions, 378. 



SOME OF THE PRINCIPAL INSECTS As SOCIATED WITH THE PINE 



TROUBLE, ........ 379 



The Scolytids, 379. Some general features and habits, 379. 

 General habits, 379. Their preference for coniferous trees, 379. 

 Grouped according to habits, 380. The mines or galleries, 381. 

 Distribution of species, 385. Natural enemies, 386 Predaceous 

 enemies, 386, Parasitic insect enemies, 386. Parasitic diseases, 

 387 Birds, 387 Unfavorable climatic and other conditions, 387. 



FRIENDS OF SCOLYTIDS, ....... 387 



Insect friends, 388. Forest fires, 388. Climatic and other natural 

 conditions favorable to the existance of Scolytids, 389. 



PREVENTITIVES AND REMEDIES. ...... 389 



Preventives . . . . . .389 



Meniwlii'* ... /. 390 



A Knowledge of the Insects and their Habits May Prevent Serious 



losses from their Ravages, . . . . . 391 



DESTRUCTIVE BARK-BEETLES, ...... 392 



The genus Dendroctonus, 392. D. terebrans, 392. D. rnfipennis, 

 393. D. simplex, 394. D. frontalis, 394. 



THE DESTRUCTIVE PINE BARK BEETLE, .... 394 



Descriptions, 394. The egg, 396. Larva, 396. Pupa, 396. Gal- 

 leries, 897. Life history, 401. Stages of development, 401. 

 Number of broods, 401. Habits, 403. Habits of flight, 406. 

 Distribution, 407. Host plants, 407. Natural enemies, 408, 

 Parasitic enemies, 408. Predaceous enemies, 409. Robbers, 410. 

 Birds, 410. Diseases, climatic conditions, etc. 411. Friendly ele- 

 ments, 411. Remedies, and preventitives, 412. Future outbreaks 

 liable to occur, 412. 



Characteristic features of injury to forest and shade trees by Den* 



droctonus frontalis, ..,.., 413 



THE TURPENTINE BARK-BEETLE, ..... 415 



Description of adult, egg, larva and pupa, 415. Habits and life 

 history, 416. Character of injury, 419. Kind of trees attacked, 

 420. Natural enemies, 42. 



THE GENUS TOMICUS, ...... 421 



T. Calligraphy.*, 422. T. cacographus, 422. T.pini, 422. T avul- 

 sus, 422. T. caelatus, 423. 



APPENDIX. 



OF INSECTS COLLECTED BY THE AUTHOR FROM SPRUCE AND 



PINE IN WEST VIRGINIA, 425 



