6 BULLETIN 95, U. S. DEPARTMENT OF AGRICULTURE. 



continues for another year in the same condition in which the first 

 winter was passed. Usually this retarded part of the brood emerges 

 at the end of the second winter or spring. 1 This is an adaptation 

 which to a certain extent accounts for the continued infestation of 

 certain species of insects in the seed of forest trees. In the case of a 

 species of gnat which infests the cones of white fir it was found that 

 the entire brood of insects which destroyed the 1911 crop of seed on 

 an area in northern California did not emerge at all in the spring of 

 1912, but remained in the pupal state through the summer of 1912 

 and the following winter. The adult flies finally emerged in the spring 

 of 1913. Under this adaptation it would appear that only a con- 

 tinued failure of the crop through a series of years would result in the 

 reduction of the numbers of the infesting species on a forest area. 

 Undoubtedly other agencies are responsible for the uninfested con- 

 dition of the seeds of certain trees during some seasons. 



INDICATIONS OF INSECT DAMAGE. 



Attack of the cone beetle in the seed crop is indicated by a small 

 entrance hole at the base of the cone, with castings or small pitch 

 tubes, during the early summer; later, by the brown, withered appear- 

 ance of the cone. 



The attack of the cone moth may sometimes be recognized by 

 little masses of pitch and larval castings on the surface of the cone 

 and sometimes by withered cones, but it is best to look for the cater- 

 pillar among the scales and in the seed and pith. It is always best 

 to cut the cone open, sectioning it several different ways, in making 

 the examination. 



The attack of the fir-cone maggot can also be found by cutting or 

 breaking the cone open. The larval mines will be found in the scales 

 and seeds, in which will usually be found the small, white, active larvae. 



The seed chalcidids show no external evidence, and the seeds must 

 be sectioned or otherwise opened to find the larvae of these insects. 

 Unless test is made the amount of damage can not be determined, 

 and seed that is badly infested may be taken as sound. 



METHODS OF PREVENTING LOSSES. 



There are areas of light infestation by these insects in certain 

 species of trees, and there are areas where the damage is very heavy. 

 The amount of infestation in the seed may also vary with succeeding 

 seasons. A careful examination of the cones before the seed matures, 

 during July and August, will usually reveal immature stages of the 

 seed-infesting insects. If cones of the past season are examined 

 during the winter and spring, they will indicate whether or not the 



1 This retarded emergence has not been observed in the case of the cone beetles, but it has been 

 observed in the more important cone worms, fir-cone maggots, and seed chalcidids. 



