1912] Hood — New Genus and Species of North American Thysanoptera 115 



lobed; all spines present, capitate, moderate in si.-^e, the pair at the posterior an- 

 gles longest. Pterothorax slightly narrower than prothorax, broadest in front, 

 sides nearly straight. Legs rather short and stout; fore tarsi armed with a very 

 small, acute tooth; femora concolorous with body; tibite usually paler, shaded in 

 basal half with brownish ; tarsi pale. 



Abdomen usually broadest at segments 5 and 6, thence the sides converge roundly 

 to base of tube. Tube about two thirds as long as head, twice as long as basal 

 width, and a little more than half as wide at apex as at base; terminal bristles two 

 fifths longer than tube. 



Measurements: Total length 1.14 mm.; head, length .144 mm., width .127 mm.; 

 prothorax, length .102 mm., width (inclusive of coxae) .216 mm.; pterothorax, 

 width .210 mm.; abdomen, width .256 mm.; tube, length .098 mm., width at base 

 .051 mm., at apex .029 mm. Antennal segments: 1, 30/-/-; 2, 42/j'.; 3, 36/j'-; 4, SS/jt; 

 5, 41/.'.; 6, 3o7^-; 7, 38/./-; 8, 23/.i; total length of antenna, .29 mm.; width at seg- 

 ment 4, .040 mm. 



Female: forma macroptera. — Differs from the brachypterous form only in the 

 presence of wings (M'hich are clouded with brownish and narrowed at middle) and 

 the increased development of the pterothorax. 



Male: forma hrachyptera. — Length abput .98 mm. Fore femora slightly swollen; 

 tarsal tooth scarcely larger than that of female. Abdomen slender; tube with 

 scale at base. 



DescriKed from fifty-three females — three of wh,ich are mac- 

 ropterous — and sixteen males, from the following localities: — 

 Illinois: Boskydell, Carbondale, Dubois, Hillery, Lyons, Pulaski, 

 Sumner, TJrbana. Michigan: Baldwin. MistSOuri: Wittenberg. 

 Nebraska: Lincoln. Maryland: Plummer's Island (in the Poto- 

 mac, near Washington, D. C). Specimens were kindly contri- 

 buted by Charles A. Hart, Lindley M. Smith, Robert D. Glasgow, 

 James Zetek, Henry E. Ewing, W. L. Mc Atee, A. G. Vestal, and 

 G. H. Coons. 



Type locality. — Urbana, Illinois. 



This little species is one of the commonest and widely distri- 

 buted North American Phlceothripids, and occurs throughout the 

 year under loose bark of apple, cherry, Cottonwood, hickory, maple, 

 oak, osage-orange, sycamore, and willow. The long-winged form 

 is found from January to July, occasionally in flight. 



From Z. minutus Uzel, the common Old W'orld species to which 

 it is closely related, it may readily be distinguished by the longer 

 prothorax which is lobed behind, the armed fore tarsi, and the 

 predominance of short-winged individuals. In minutus the short- 

 winged female is unknown. 



