On the Variation and Abundance of Sirex Nitidus Harris

Dr. Frederic T. Lewis has obtained a large and interesting series of a horntail referable to Sirex nitidus Harris, at his summer place at Randolph, N.H. On July 29, 1930, Dr. Lewis sent me 18 males and 5 emales; on August 3, 24 males and 25 emales; on August 7, 9 males and 17 2emales; on August 10, 5 males a.nd 4 emales; on August 22 to 29, 6 males and 15 females; in all, 62 males and 68 emales, a total of 130. Having but one male and three 2emales of this species after twenty-six years collecting in New England, this large number came as a great surprise. The series is especially interesting in showing a remarkable range of variation. The smallest male measures 13 mm., the largest 25 mm., and the smallest emale is 12 mm. and the largest 24 mm. This measurement does not include the ovipositor. Between the two extremes there is a complete gradation in size. There is also a great variation in the color of the two sexes, which together with the problem of distribution make the species of the genus Sirex difficult to define. In determining this species there are many obstacles. It does not agree with S. cyaneus Fabr. as defined by either Bradley or Waterston, but is closer to S. noctilio Fabr. as redescribed by Waterston. It differs, however, from that species in having all the femora of the male bright yellow not "darkened," the posterior tibim and the first three joints of the tarsi black. The female has the same 2orm of cornus and length of ovipostor as S. noctilio, but