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Indiana University Studies 



and cracked, sometimes set with low, raised lines or irregular rows of 

 low tubercles radiating more or less from the slightly pointed tip of 

 the gall ; brilliant, rich apple red when fresh, with some apple green 

 and lighter green, becoming bright brownish yellow on aging, weather- 

 ing darker. Internally like compacted sawdust, crystalline, spongy only 

 in old and weathered specimens; with a hard, woody core originating 

 from the point of attachment, the core flaring and somewhat branching 

 in the center of the gall, with the larval cells arranged radiantly in 

 the extremities of this core, mostly in a single layer centrally of the 

 gall; each cell averaging 2. x 4. mm., with a distinct and easily separable, 

 thin-walled lining. Laterally, less often terminally, attached by a small 

 point, sessile on twigs of Quercus agrifolia and Q. Wislizenii. 



RANGE. — California: from the Mexican border to Dunsmuir and 

 Ukiah. 



This is one of the most prominent of Californian galls, 

 being surpassed in size and abundance only by Andricus cali- 

 fornicus. Both species are known as oakapples. As with 

 calif orniciis, the possibility of more than one variety, each 

 with its own intensely interesting biologic problems, has been 

 heretofore entirely overlooked. The biologist who will learn 

 what these two species should easily disclose in ten years or 

 less work on the held, may contribute as important data as 

 we yet possess on such problems as the nature of alternation 

 of generations, distribution factors, and host effects, for in- 

 stance. 



Adults mature in early spring, earlier at southern local- 

 ities. The field data indicate that northern varieties (see 

 variety pomiformis) complete the life cycle in a year, with the 

 possibility of an alternation of generations; while southern 

 varieties (see maculipennis) take two years or more to ma- 

 ture, and may not have an alternate generation. This must 

 be considered a suggestion, to be verified only by experimental 

 work. If this is shown to be the true condition, it confirms 

 my previously expressed opinion (1920, Bull. Amer. Mus. Nat. 

 Hist., XLII, p. 372) that alternation of generations is an ex- 

 treme development of seasonal dimorphism. 



If galls are collected too soon before maturity, the larvse 

 will develop into adults altho few insects will emerge. One 

 finds this the case with galls in the laboratory more often 

 than with galls in the open. Under adverse conditions in the 

 field, such as a season of drought, there may be a similar de- 

 struction of adults before emergence. An experience with 

 this species in the laboratory alone, in connection with some 



