386 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
female, whose ovipositor is relatively short, stiff, and toothed at 
tip ; and those of Mole-crickets are laid in underground chambers 
excavated by the female. 
The feature of most popular interest connected with the family 
is undoubtedly the sounds which they produce by stridulation. 
Allusions to these so-called 'songs' are constantly appearing in 
literature. They are, of course, instrumental instead of vocal in 
character, but serve the same purpose of communication and 
expression of the emotions as true songs. The study of these is 
not a whit less interesting than the study of bird music and 
references are frequently made to them in the succeeding pages. 
In some species the songs take the form of a series of chirps or 
beats, increasing with the temperature from about 40 to 160 per 
minute, and so regularly that it is possible to compute the approx- 
imate height of the mercury by this means. For this purpose the 
formula 
T = 50+Nzi5 
4 
has been used for a species of Tree-cricket {Oecanthus niveus). 
In this formula, 50 = the temperature in degrees Fahrenheit at 
which activity begins to be regular, N = the number of chirps 
per minute, 40 = number of chirps per minute at 50°, 4 = rate of 
increase for each degree of temperature, and T = the temperature. 
Hebard's Revision of Nemobius gives diagrammatic figures 
illustrating the terminology of the cells and veins of the tegmina, 
which will serve for Grylliis also. Fulton's "Tree-crickets of 
New York " is the best w^ork on that group. The other references 
cited below present the latest results of taxonomic study or con- 
tain particularly helpful notes, figures, or bibliography. 
Gryllotalpa: Rehn and Hebard, " Studies in the Dermaptera and Orthoptera 
of the coastal plain and Piedmont region of the southeastern United 
States." Proc. Acad. Nat. Sci. Phila., April 1916, p. 277. 
Gryllus: Rehn and Hebard, "The genus Gryllus as found in America." Proc. 
Acad. Nat. Sci. Phila., May 1915, p. 293-322, pi. 4.— Lutz, F. E., "The 
variation and correlations of certain taxonomic characters of Gryllus." 
Carnegie Inst, of Wash., publ. no. 101. 
Nemobius: Hebard, M., "Revision of the species of the Genus Nemobius 
found in North America north of the Isthmus of Panama." Proc. Acad. 
Nat. Sci. Phila., June 1913, p. 394-492. 
Neoxabea. See next item. 
