306 THE LIVING ANIMALS OF THE WORLD 
short, and constricted at the base. The flies seldom measure more than half an inch across the 
wings. Some galls are hard, like the one found on the Turkey oak, from which ink is made; 
while others are large and juicy, resembling cherries, or small apples, among which is the 
so-called apple of Sodom. Others, like the Bedeguar, which is found on roses, have a mossy 
appearance. The latter are produced by a small black saw-fly, with part of the legs, and, 
in the female, the base of the abdomen, red 
beneath. 
Some of the smaller gall-flies do not pro- 
duce galls, but are parasitic on other insects; 
but galls are very liable to the parasitic attacks 
of other insects, especially to those of smali 
brilliant metallic green four-winged flies, belong- 
ing to an allied family, with very few nervures, 
but with a black membranous spot on the 
front edge of the fore wings, and angulated 
antenne. Many galls do not begin to grow 
until the larva is hatched and begins to eat. 
We now come to five or six families of 
parasitic species, popularly called ICHNEUMON- 
FLIES, and immensely numerous and varied. 
L 
Photo by) th. P. Dando, F,Z.S.] [Regent's Park There are probably considerably over 2,000 
PINE-BORING WASP (FEMALE) species in England alone; but they are com- 
Formidable in appearance, but quite harmless paratively little known or studied. Some of 
these have beautifully delicate wings, fringed 
with long bristles, and are among the smallest insects known, being of quite microscopic 
dimensions. These are parasitic on the eggs of various insects, and some are aquatic. But 
the more typical ichneumon-flies are of larger size, often measuring more than an inch across 
the wings. Their bodies are usually black or yellow, and there is often an irregularly shaped 
space in the middle of the fore wing, where the veins of the wing converge. In these 
flies the ovipositor is very short; but in others it is of great length, especially in the case 
of the largest British insect of this group, which is 
parasitic on the larve of the great black-and-yellow 
wood-wasp, of which we have already spoken. This 
parasite is as large as the wood-wasp, but much more 
slender; it is black, with red legs, and two white dots 
on each segment of the abdomen. The ovipositor, which 
looks like three black threads, is as long as the whole 
body. 
The numerous parasites of which we have spoken 
usually deposit their eggs in punctures in the bodies | 
of caterpillars or other immature insects, which the grubs | 
devour from within during the life of their victim, | 
leaving it to die when they themselves have reached , 
their full growth. Photo by 1", P. Dando, F.Z.S. 
Intermediate between the boring and stinging insects PINE-BORING WASP (MALE) 
of this order comes the small family of the RUBY-TAILED Smaller than the female, and very different in appearance 
FLIES. These are brilliantly coloured bronze-red, blue, 
or green metallic four-winged flies, with the thorax covered with large depressions, and the 
abdomen smooth, and usually composed, as seen from above, of one large, smooth joint, and 
one or two much smaller coarsely punctured ones beyond it, the last ending in a variable 
number of short teeth. They roll themselves up in a ball when alarmed, and are parasites, 
depositing their eggs in the nests of other insects. An entomologist once saw a ruby-tailed 
