1930] Variation and Abundance of Sir ex nitidus 
281 
ON THE VARIATION AND ABUNDANCE OF SIREX 
NITIDUS HARRIS 
By Charles W. Johnson 
Boston Society of Natural History 
Dr. Frederic T. Lewis has obtained a large and inter- 
esting 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 females; on August 3, 
24 males and 25 females; on August 7, 9 males and 17 
females; on August 10, 5 males and 4 females; on August 
22 to 29, 6 males and 15 females; in all, 62 males and 68 
females, a total of 130. Having but one male and three 
females of this species after twenty-six years collecting 
in New England, this large number came as a great sur- 
prise. 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 female 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 vari- 
ation 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 1 or Waterston 2 , 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 tibiae and the first 
three joints of the tarsi black. The female has the same 
form of cornus and length of ovipostor as S . noctilio, but 
1 J. C. Bradley, Journ. Ent. and Zool., voL 5, p. 19, 1913. 
2 James Waterston, Bull. Ent. Research, vol. 5, p. 221, 1928. 
