Systematic Course. 85 
bee, comparing them with his sketches of the corresponding organs in 
the cockroach, 
The abdomen in the female usually ends with an ovipositor, which is 
often modified into a sting. In the latter case it is connected with a 
gland secreting a poison in which formic acid is probably the most 
prominent ingredient, The sting is a grooved spine enclosed in a sheath, 
from which it can be freely extended. 
The Hymenoptera arose comparatively late in geological history, and 
comprise some of the most highly specialised insects. Some twenty- 
five thousand species are said to have already been described from differe 
ent parts of the world, and vast numbers of minute forms, especially in 
India, are still unclassified. 
The following are the more important groups :— 
I.—Teresrantias—The female with ovipositor. 
a, Phytophaga.—Abdomen sessile, the larvae resemble caterpillars. 
Include the Tenthredinide. 
b. Gallicola.—Abdomen stalked. The larve inhabit galls. 
Include the Cynipide and the Blastopbaga. 
e. Entomophaga.—Abdomen stalked. Larvee parasitic on other 
insects, 
Include the Ichneumonide and Chalcidide. 
II,—Acusara.—The female with ovipositor more or less modi- 
fied to serve as a sting. 
Include the Formicide, Chrysidide, Apide, Vespide 
Fossoria, Scoliide, and other groups of less importance, 
Tenthredinide (Saw-flies)—These Hymenoptera can easily be recog- 
nised by the fact that they have no constriction between the thorax 
and the abdomen. The larve resemble caterpillars in appearance, but 
can easily be distinguished from caterpillars by their indefinite number 
of prolegs and single pair of large ocelli. 
Saw-fly larvz feed upon the leaves of plants, and occasionally do a 
little damage in gardens as defoliators (¢.g., the species common upon 
rose bushes in the Dehra school compound). The eggs are laid in the 
bark of the twigs of the food plant, and result in a large wound, which 
may be injurious if the shoot attacked happens to be the leading one, 
Saw-fly larve can be destroyed by spraying with arsenical insecticides 
in cases where this treatment is worth adopting. 
The rose bushes in the school compound usually afford a plentiful 
supply of saw-fly larve in various stages of development, The 
Moseum also contains specimens of the imago and cocoon. 
D2 
