34 PROCEEDINGS OF THE NATIONAL MUSEUM voi-. 80 



series at the gipsy moth laboratory, reared July, 1917, from Ex- 

 artema sericorana Walsingham, taken at Westerly, R. I. 



22. MACROCENTRUS INSTABILIS, new species 



Most similar to laspeyresiae^ but differing in the usually narrower 

 and smoother face, the shorter malar space, the usually entirely 

 brown stigma, in the mesoscutum posteriorly being usually more 

 sharply emarginate, with the scutellar furrow not strongly trans- 

 verse, in the relatively longer and narrower second abdominal ter- 

 gite, the usually stronger sculpturing of second and third tergites, 

 and the somewhat smaller size. 



Female. — Length 5 mm. Head strongly transverse, much wider 

 than thorax, eyes large, prominent; malar space shorter than basal 

 width of mandible; face, viewed from in front, not or but little 

 broader than long, entirely smooth and shining; clypeus strongly 

 convex, rather long, broadly very weakly emarginate at apex, 

 smooth; distance from clypeal foveae to eyes less than length of 

 clypeus; palpi slender, longest segment of maxillary palpus dis- 

 tinctly longer than second segment of antennal flagellum, apical seg- 

 ment of labial palpus lengthened; antennae longer than the body, 

 49-segmented in type. 



Thorax slender; prescutum prominent; notauli minutely indis- 

 tinctly foveolate; propodeum very finely transversely rugulose, 

 smooth at base laterally; sides of pronotum, mesopleura and meta- 

 pleura polished; coxae polished; apical teeth of trochanters dis- 

 tinct but usually not more than three or four on each trochanter; 

 radius arising from middle of stigma; radial cell extending very 

 nearly to extreme apex of wing; first discoidal cell much longer 

 than the first cubital; nervulus usually postf ureal by as much as its 

 own length; submedian cell with a hairless area apically; mediella 

 nearly three times as long as lower abscissa of basella, the latter just 

 about as long as nervellus and but little longer than upper abscissa 

 of basella. 



Abdomen but very little longer than head and thorax combined; 

 first tergite twice as long as broad at apex, closely finely longitudi- 

 nally aciculate, impressed at base, spiracles a little farther from 

 each other than from base of tergite; second tergite slightly longer 

 than broad, closely finely completely aciculate, the lateral depres- 

 sions usually narrow at base; third tergite mostly finely aciculate 

 on basal half; rest smooth; ovipositor sheaths a little longer than 

 the body. 



Head testaceous; palpi and base of mandibles very pale yellow; 

 antennae mostly yellowish, the basal flagellar segments darker ; dor- 

 sum of thorax mostly piceous in type; propodeum blackish; pleura 



