THE ICHNEUMON FLIES. 293 



are made in the same tree. The nests are well and carefully 

 made of mud, roots, and grasses, about four inches in depth, 

 and warmly lined with horsehair and very fine grasses. The 

 fact that the bird possesses this capability of nest-building, 

 gives more interest to the occasional habit of sharing its home 

 with the osprey — a pnvilege of which it seems to avail itself 

 whenever an osprey's nest is within reach. 



The colour of this bird appears at a little distance to be black, 

 but is in reality a very deep purple, changing in different lights to 

 green, violet, and copper, and having a glossy sheen like that of 

 satin. 



We now pass to the Parasitic Insects. As this work is m- 

 tended to describe dwellings which are in some way formed by 

 the creatures, it is necessary to exclude all the parasite insects 

 that may exist upon the animal, and make no habitation, such 

 as the ticks, as well as those which are merely parasitic within 

 the animal, such as the various entozoa. 



Of Parasitic Insects, the greater number belong to that group 

 of hymenoptera which is called Ichneumonidas, and which em- 

 braces a number of species equal to all the other groups of the 

 same order. Being desirous of producing, as far as possible, 

 those examples of insects which have not been figured, I have 

 selected for illustration several specimens which are now in the 

 British Museum, one or two of which have only been recently 

 placed in that collection. 



The best known of all the Ichneumonidae is that tiny creature 

 called Microgaster glomeratus. 



A group of these insects and their cells is now before me, and 

 will be briefly described. 



Small as it is, this tiny insect is extremely valuable to us, and 

 to the gardener is beyond all value, though, as a general rule, 

 the gardener knows nothing about it. Where it not for this 

 ichneumon, we should scarcely have a cabbage or a cauliflower 

 in the garden; for the noisome cabbage caterpillars would 

 destroy every leaf of the present plant, and nip the growth of 

 every bud which gave promise for the future. 



