66 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



with numerous short stiff setae. Mucro (pi. 24, fig. 275) as long as 

 hind unguiculus, in lateral aspect strongly rounded ventrally, biden- 

 tate; apical tooth relatively long, hooked; anteapical smaller, sub- 

 erect. Rami of tenaculum quadridentate ; corpus with a single seta. 

 Clothing of short setae ; outstanding sensory setae also short. Integu- 

 ment smooth. Maximum length, 1 .2 mm. 



Cotypes.— U.S. l<iM. no. 42985. 



Distribution.— ^Recorded as follows: 



Louisiana: Baton Rouge, March 9, in cane trash, C. L. Stracener. 

 Genus ARCHISOTOMA Linnaniemi 



Isotoma Packard, 1877, p. 52 (part). 

 Archisotoma Linnaniemi, 1912, p. 118. 



Genotype. — Isotoma besselsii Packard. 



Head broad and long; front low-arched. Eyes and postantennal 

 organs present. Fourth antennal segment relatively short, with a 

 ternunal lobe, a subapical papilla and a few olfactory setae. Third 

 and fourth abdominal segments subequal in length. Genital and 

 anal segments ankylosed. Anus caudal. Hind femur with a distal 

 outer thornlike process. Tibiotarsus with a distal subsegment. 

 Outer lamella of unguiculus absent. Tenent hairs absent. Manu- 

 brium longer than dentes, with a long coxal, or basal, segment, and 

 naked ventrally. Dentes stout, subcylindrical, smooth dorsally. 

 Mucrones tridentate, not lamellate. Rami of tenaculum quadri- 

 dentate; corpus with a large anterior accessory lobe, and without 

 setae. Bothriotricha present. Integument smooth. 



ARCHISOTOMA BESSELSI (Packard) 



Plate 14, Figures 147-149; Plate 15, Figures 150-155 



Isotoma hesselsii Packard, 1877, p. 52.— MacGillivray, 1891, p. 273; 1896, p. 



52. — VON Dalla Torre, 1895, p. 10. — Davenport, 1903, p. 6. — Bacon, 



1912, p. 841; 1914, p. 148. 

 Isotoma pulchella Moniez, 1890, p. 431.— Denis, 1923, p. 221. 

 Isotoma besselsi Schaffer, 1900a, p. 248. — Folsom, 1901, p. 162. — Axelson, 



1905b, p. 30.— Wahlgren, 1906c, p. 16. 

 Isotoma spitzbcrgenensis Lubbock, 1898, p. 616. — Carpenter and Evans, 1899, 



p. 252.— Skorikow, 1900, p. 193. 

 Isotoma arctica Scherbakov, 1899a, p. 47; 1899b, p. 5. 

 Isotoma janmayensis Wahlgren, 1900a, p. 354. 

 Proisotoma besselsi Linnaniemi (Axelson), 1907, p. 73; 1911, p. 14. 

 .4rc/izso<o»ia besseisz Linnaniemi (Axelson), 1912, p. 119. — Brown, 1918, p. 186; 



1925, p. 157.— Folsom, 1919b, p. 277.— Denis, 1923, p. 221; 1924c, p. 562; 



1926, p. 16.— Womersley, 1924a, p. 32; 1924b, p. 169.— Remy, 1928, p. 

 65.— Handschin, 1929, p. 59. 



Description. — Gray, bluish gray, blue, or blackish; in alcohol more 

 or less greenish. Borders of body segments pale or white, giving the 

 insect a banded appearance. Posterior region of head and sides of 

 body with unpigmented spots. Body slender. Head broad, long 



