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Indiana University Studies 



hairy; foveae distinct or indistinct, smooth or rugose at bottom; abdomen 

 smooth, more or less finely punctate and even indefinitely reticulated, 

 largely naked, very sparsely, rather finely hairy, the second segment 

 covering a full half of the area; cubitus distinctly continuous; length 

 2.2-3.0 mm. 



GALL. — Slight twig swelling, elongate in two varieties, globoid in 

 one. Monothalamous or polythalamous, one to fifty or more cells in a 

 cluster. The swelling slight, two or three times the normal stem diam- 

 eter, up to 8. mm. in diameter, averaging 60. mm. long in two varieties, 

 8. mm. long in one; covered with normal bark. Internally solid except 

 for an irregular, more or less continuous cavity completely filled by 

 crowded, distorted, larval cells, each cell separate, with a distinct 

 lining, but not separable. Near the tips of twigs of Quercus stellata 

 and Q. breviloba. 



RANGE. — Texas: Austin, Probably thruout a part of Texas and 

 Louisiana. 



Dr. Patterson discovered and bred the insects of all the 

 following varieties. 



The insect of variety elongatus is very closely related to 

 the varieties of Plagiotrichus frequens, differing only in being 

 less black and in having the thorax more hairy. The insect 

 of variety rufopleurx shows some relation to Plagiotrichus 

 hatatoides, having the antennse of uniform color and the ab- 

 domen very faintly reticulated; but it differs decidedly in 

 many other respects. On a whole, tho, these three Texas 

 insects are more closely related to each other than to the in- 

 sects of the other species; so it is worth treating them as a 

 distinct species. Beyond exhibiting the same generic char- 

 acters, the galls are not similar to those of either frequens 

 or hatatoides. 



The three insects differ in regard to a few characters only, 

 but these are so differently combined as to make three re- 

 markably distinct varieties. Any one of them might be con- 

 sidered intermediate between the other two. This may be 

 more evident if one thinks of three varieties having nine 

 points in respect to which they vary. Each of these varieties 

 may have three characters which are unique to it, three which 

 are shared with one of the other varieties, three which are 

 shared with the third variety. This may be represented as 

 follows : 



Variable characters 123456789 

 Not unique to variety A 1 2 3 4 5 6 



Not unique to variety B 4 5 6 7 8 9 



Not unique to variety C 1 2 3 7 8 9 



