341 



the brook was 25 cin. deep. I took many stones from the water, and 

 found females of Agriotypus sitting on some of them. The agrio- 

 typized cases of Silo nigricornis, Pict., which I found there enclosed 

 fully grown imagos, which had already cast off the pupal skin, and 

 were ready to escape from the water, and rather rarely, fully de- 

 veloped nymphs. 



As the imago of Agriotypus armatus (Fig. A) was so well described 

 by Curtis, it would be useless to give any further description of it 

 here ; T will add only, that all my examples caught in Bohemia are 

 much smaller than the type examples preserved in the collection of 

 the Natural History Museum in London, many of them being only 

 half as large. 



The fully grown larva (Fig. D) is maggot-shaped, with a distinct 

 chitinous head, which bears small simple eyes on the sides, but on 



which I could not detect the an- 

 tenna?. The mouth parts (Fig. F) 

 .are biting and well developed; their 

 .general structure is not very unlike 

 that of the jaws of a caterpillar. 

 Labrum (Lr) membranous, very 

 broad and short ; mandibles (M) 

 very strong and, if viewed from 

 above, triangular, with a coarsely 

 „. p serrate cutting edge; maxillae (Mx) 



rudimentary, their jaw parts membranous, and the palpi (Pm) are de- 

 veloped only as small warts ; labium (Li) broad-conical, with a large 

 opening of the salivary glands on its top, and with rudimentary wart- 

 shaped palpi (PI) on its sides. The thirteen segments of the body are 

 soft with distinct divisions. They are of a very unequal breadth, so 

 that the 1st — 3rd increase gradually, the 4th and 5th are much smaller, 

 the 6th — 8th are broadest of all, the 9th — 13th decrease again 

 gradually in breadth. The last segment bears on its end two slender 

 and adpressed hooks. 



The larva, before changing into a nymph, assumes a new shape 

 (Fig. C). The head is retracted into the following segments, the 

 divisions of which become oblique ; the head is now almost invisible. 

 The anterior part of the body (segments 1 — 8) is cylindrical, with the 

 front side straightly truncate ; the following segments become gradully 

 smaller, so that the posterior part of the body is acuminated. The 

 hooks on the last segment are porrected. This is what I will call the 

 subnymphal stage. 



