OVIPOSITION OF MEGASTIGMUS SPERMOTROPHUS 

 IN THE SEED OF DOUGLAS FIR 



By J. M. Miller, 

 Assistant in Forest Entomology, Bureau of Entomology 



The larva of a seed chalcidid, Megastigmus spermotrophus Wachtl, has 

 been very commonly recorded from the seeds of Douglas fir (Pseudotsuga 

 taxijolia) , but most of these records apply only to mature seed. The method 

 by which the larvae of this insect get into the seeds has not been previ- 

 ously described. The oviposition of the female, the period of the growth 

 at which the seeds are infested, and the subsequent development of the 

 larvse are matters on which we have no published data. 



The following is an account of the oviposition of this species observed 

 at the Forest Insect Seed Station of the Bureau of Entomology at Ash- 

 land, Greg., during the season of 191 5. 



During the season of 1914 a heavy emergence of adults of Megastigmus 

 spermotrophus from Douglas fir seed of the 191 3 crop occurred in the vicin- 

 ity of Ashland. From stored seed kept in a rearing box the male adults 

 began to emerge on April 12, and the females on April 16; 2,897 adults 

 emerged from 6^ ounces of seed, the period of maximum emergence occur- 

 ring between April 23 and May 11. A number of these adults were lib- 

 erated in a small cage kept in the laboratory. It was found that the 

 adults would not live any length of time unless fed. Pieces of blotting 

 paper saturated with sugar solution were hung in the cage and on this 

 the adults were frequently seen feeding. Young Douglas fir cones were 

 kept in the cage with the adults for a period of about three weeks; and 

 although copulation was frequently observed, no attempts were noted 

 on the part of the females to oviposit in the cones. 



During the season of 191 5 another effort to secure a record of oviposi- 

 tion in a rearing cage met with far better success. Various lots of in- 

 fested Douglas fir seed were kept at the station, and the emergence of 

 the adults from this seed was quite similar to that observed in 191 4. 

 The maximum period of emergence in the laboratory occurred between 

 April 20 and May 2. From cones which were kept caged over winter 

 under outdoor conditions at the same elevation, the maximum emergence 

 occurred between May i and 16. At elevations of 3,000 to 4,000 feet 

 the emergence occurred during the latter part of May, and above 4,000 

 feet much of the emergence occurred in June. 



Many adult chalcidids were liberated at different dates between April 

 18 and May 20 in a cage considerably larger than that used in 191 4 (PI. V, 



Journal of Agricultural Research, Vol. VI. No. ■ 



Dept. of Agriculture. Washington. D. C. Apr. lo. 1916 



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