HYMENOPTERA. — TENTHREDINIDA. 105 
Hartig (which St. Fargeau gives as the T. salicis Zinm.), in the same 
plate (figs. 12—22.); and his fig. 23. is given by Hartig under the 
name of N. betula. The last-named author has also figured the larva 
and imago of another species (N.abietum ), with details (pl. 4. f. 11—24.), 
The 20-footed larva (fig. 71. 7.), of Croesus septentrionalis, which 
lives in society upon the elm, protrudes a series of black fleshy 
tubercles between the abdominal legs when it is alarmed, but which 
are withdrawn into the body when the danger is passed. (De Geer, 
Meém. tom. ii. pl. 37. f. 24—28.) It is also figured in the Entomol. 
Magazine, vol.i. pl. 1. f.5. The larva of another species of the same 
genus, of a fine green colour, with 9 rows of black dots, is found upon 
Salix viminalis. It is figured by Geedart (t. 1. pl. 19.), Frisch 
(st. 6. t. 4. f. 1—7.), Réaumur (tom. i. pl. 1. f. 18.), and De Geer 
(tom. ill. pl. 38. f. 1.), and is supposed by Dahlbom to be the Nematus 
varus Villaret (Ann. Soc. Eint. de France, tom. i. pl. 11. f. 8.); T. 
salicis Zinn., Réaum., tom. v. pl. 11. f. 10. 
De Geer has also figured the larve of several species of Nematus, 
which are 20-footed, and are not gregarious in the larva state ; namely 
N. capraee (Mém.tom. ii. pl. 38. f.1.;) N.nigratus Hartig, Retz. (Ibid. 
f.2—4.), both on the willow ; and N. interruptus S¢. Farg., 249.; N. 
abietinus Dahl. (Ibid. 5—7.), on the fir; likewise the 20-footed larva 
of Dineura De Geerii Hartig, which St. Fargeau gives as Nematus 
varius. Frisch has figured the various states of Nematus salicis 
(Beschr. §e. vi. 4.) ; Dahlbom has also described the larvee of many 
species of Nematus, which he divides into those which are gregarious 
or solitary. A correspondent of the Mag. Nat. Hist. (vol. vii. p. 423.) 
has published an account of the devastation committed by Nematus 
capree to osiers, producing a loss of at least 2004, by devouring the 
leaves annually, and thus destroying the young plants. 
Several small species of Nematus deposit their eggs in the young 
shoots of the willow, causing the formation of woody galls upon the stem 
in which several larvee reside in society, and undergo all their changes 
(N. medullarius Hartig, De Geer, tab. 39. f. 1—13.; N. pentandrze 
Dahlb. ; T. salicis pentandre Vill.), or of globose spongy pedunculated 
galls along the main rib of the leaf. (De Geer, tab. 38. f. 26—31.; N. 
intercus Panzer, Dahlbom; N. gallarum Hartig, De Geer, tab. 38. f. 
26—31.), in which a single inhabitant resides durihg the larva state. 
Another kind of gall is produced upon the leaves of various kinds of 
* Mr. Paget (Nat. Hist. Yarmouth, App.) states that the larvee of this species are 
very abundant on willows, entirely stripping many of these trees of their leaves. 
