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Indiana University Studies 



Andricus operator (Osten Sacken) 



FEMALE. — Generally rufous; antennae with 12 segments; median 

 groove almost lacking ; many of the wing veins very faint ; areolet about 

 closed. HEAD : Fully as wide as the thorax, distinctly enlarged behind 

 the eyes; rufous, the tips of the mandibles piceous; finely granulose, 

 almost naked of hairs except about the mouth. Antennae yellowish, 

 slender in the bisexual female, stouter in the agamic female, of mod- 

 erate length, slightly thicker terminally, with 12 (13) segments, the 

 second shortest but quite elongate, the third only slightly longer than 

 the fourth, the last more than twice the length of the preceding or 

 obscurely divided. THORAX: Of a uniform rufous; mesonotum very 

 finely rugulose rugose, almost naked but with a few, very short hairs; 

 parapsidal grooves widest posteriorly, continuous, rather abruptly di- 

 vergent anteriorly; median groove almost absent or just discernible at 

 the scutellum; anterior parallel lines barely indicated in the bisexual 

 female; lateral lines fine, smooth; scutellum small, rather longer than 

 wide in the bisexual female, wider than long in the agamic female, 

 rugose, with the two foveas distinctly separated by a fine ridge; pro- 

 notum laterally very finely rugose; mesopleur^E wholly, very finely 

 rugose, aciculated centrally, naked. ABDOMEN: Wholly rufous brown, 

 darkest more posteriorly especially dorsally; smooth, naked, edges of 

 segments finely, faintly punctate; quite a little longer than wide, hardly 

 produced dorsally, and the edges of the segments not far from vertical 

 in the bisexual female; somewhat produced dorsally, the edges of the 

 segments strongly oblique in the agamic female; segment two covering 

 two-thirds of the area; ventral spine fine, rather short; ventral valves 

 toward the vertical. LEGS: Ivufous, including the coxae; tarsal claws 

 rather fine, simple. WINGS: Clear; edges not ciliate; subcosta and 

 cross veins a medium brown, the other veins very fine and faint, the 

 terminal part of the subcosta very faint or lacking; areolet closed; 

 cubitus very short and faint; radial cell of moderate length, slender, 

 open, the second abscissa of the radius almost straight; the first abscissa 

 weakly angulate. LENGTH: Of the bisexual female, 1.7-2.7 mm.; of 

 the agamic female, 3.2-3.5 mm. 



MALE. — Differs from the female of the species as follow^s: Face 

 yellowish; antennae yellowish, decidedly thicker than in the female, with 

 14 segments, the third clavate, incised basally, the last not as long as 

 the preceding; abdomen elongate, slender, the second segment covering 

 three-quarters or more of the area; legs yellowish; length averaging 

 less than in the female. 



GALL. — An oval larval cell, mostly inseparable from and occupying 

 most of a thin-walled, seed-like capsule. These capsules woolly, clus- 

 tered in the bisexual generation, naked in the agamic generation, pro- 

 ducing the following forms of galls ; on eastern American black oaks. 



Bisexual Generation: Large, compact masses of wool, irregular in 

 shape, often oval, up to 40. by 55. mm. in dimensions; the hairs at 

 first crisp, succulent; greenish, white, or rose-tinged, sometimes deep 

 red; becoming straw color or golden brown upon aging, finally weather- 

 ing bluish gray or black, shrivelling considerably. Within the wool. 



