144 LEAVES FROM MY NOTE-BOOK. 



the fore-legs. In Libellulid larvae, the side-pieces can be brought 

 together in the middle line, like the jaws of a rat trap, which 

 they further resemble in their toothed edges. 



A number of aquatic insects, like the terrestrial Ichneumons, 

 lay their eggs in the bodies of living insects. The larvae hatch out 

 and devour the bodies of their hosts little by little, delaying fatal 

 injury till the parasite is full grown. " One such form, Agriotypus^ 

 preys upon caddis worms. . . The history of this parasite has 

 recently been more fully explored by Klapalek.'^ In Bohemia, 

 Klapalek finds that Agriotypus commonly attacks the case of a 

 Caddis worm, known by the name of Silo pallipes. On warm 

 days in April the Agriotypi may be seen swarming like ants about 

 the banks of the brooks, and also flying above the water. The 

 females descend stems and grasses into the water, and creep under 

 stones in the bed of the stream in search of victims. The larva 

 of the parasite spends its whole life under water and inside the 

 case of a Caddis worm. Its host is not mortally injured till it 

 has prepared for pupation. Like a healthy Caddis worm, it makes 

 its case fast and closes it up. Then the Agriotypus larva makes a 

 final end of its victim, devouring it, and cramming the remains 

 into the hinder part of its case. It then proceeds to move the 

 case by a long band formed from its own salivary glands, which is 

 the external indication of an agriotypised Caddis." Within this 

 extemporised cemetery it spins its cocoon, and winters before 

 emerging as a winged fly (Fig. 7). A ghastly history, closely 

 parallelled by that of the Sphex wasp. 



The larva of the Alder fly, Sialis, is guided by one of those 

 extraordinary instincts which suggest that the animal is directed by 

 some intelligent power, to which one can ascribe wisdom, but not 

 beneficence. The larva of Sialis, hatched under water, and living 

 in water all through its early life, comes upon land in May or June 

 to pass through its pupal stage. For this purpose it will travel far 

 from its native pool. Mr. Miall says, " I have lately found one 

 creeping on the surface of the ground six yards from the water, 

 though the season was dry, and the soil common garden mould. 

 This larva had climbed up a concrete wall, made its way through 

 a thicket of cotoneaster, and reached an open flower-bed. When 



* Ent. Monthly Mag., 1889, p. 339. 



