INSECT ENEMIES OP WESTERN FORESTS 15 



INSECTS AFFECTING SEED PRODUCTION 



The natural reproduction of forests, the artificial reforestation of 

 denuded areas, and the future supply of timber depend to a consider- 

 able extent upon the production of a prolific supply of sound, unin- 

 jured seed. In most instances insect damage to tree seeds is not 

 sufficiently severe to be of any great importance; in some seasons, 

 however, insects destroy practically all the seed of certain tree species 

 in certain localities. 



Destruction of seeds may be caused by insects that attack the buds, 

 flowers, or immature cones, as well as by those that attack the seeds 

 themselves. Damage at these early stages causes wilting, blighting, 

 or premature dropping of the parts affected. The fruit or cones de- 

 veloping after insect attack may be deformed or "wormy", riddled by 

 the borings of various grubs, caterpillars, or maggots. In many cases 

 the cones show no damage, but the seeds are infested with the small 

 white larvae of seed chalcids. Even the old, hard, dry cones of cer- 

 tain pines are often mined by wood borers. The insects that affect 

 seed production in these various ways belong to a number of dif- 

 ferent orders and families, of which some w^ork only on cones or seeds 

 while others work also in the bark or cambium of succulent growing 

 shoots, stems, and tAvigs, or even in dry wood. 



Knowledge of the presence of seed-infesting insects will often pre- 

 vent the disappointment and loss attendant on the collecting, han- 

 dling, and sowing of insect-damaged seeds {58) 



2 



KEY TO DIAGNOSIS OF INSECT INJURY TO CONES AND SEEDS 



A. Injuries to cones and coniferous seeds. 



1, Cones wither and die before they are half grown. 



a. Interior mined by small, white, curled larvae or 

 by small dark-brown beetles; pine cones only, 



cone beetles, page 16. 



6. Cones deformed and interior mined by active cater- 

 pillars ; exterior with exudation of pitch or 

 webbed borings cone moths, page 16. 



2. Cones reach full growth but are riddled with insect borings. 



a. Borings made by active caterpillars which leave 

 pitchy masses of boring and excrement within the 

 cone and similar exudations at the point of en- 

 trance, or larval mines in axis and mature seeds, 

 without resinous exudations cone moths, page 16. 



&. Soft cones riddled by small white maggots which 

 leave fine excrement in tunnels, but free from 

 masses of pitch cone maggots, page 20. 



c. Hard, dry cones of pine mined by slender, white, 

 round-headed or flat-headed larvae, 



cone borers, page 21. 



B. Injuries to coniferous seeds, with or without injury to cone. 



1. Seeds show no external injury, but interior is hollowed out 



by small, white, curled, legless grubs seed chalcids, page 21. 



2. Seeds swollen and galled, containing small pink maggots, 



seed midges, page 20. 



C. Injuries to nuts or seeds of broad-leaved trees. 



1. Acorn showing no injury externally but mined by small, 



white, curled grub acorn weevils, page 22. 



2. Interior of acorn mined by active caterpiller which discharges 



webbed frass through exit hole acorn moth, page 23'. 



2 Italic numbers in parentheses refer to Literature Cited, p. 197. 



