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the experiments it can only be on account of wanting air. When 

 the band is moved directly from water to glycérine it will be 

 seen that it is always air-filled be':ween the threads, and when 

 a case having a living Agriotypus imago in it is opened in water 

 it will be seen that the imago lies imbedded in a layer of air. 



It is a well known fact that the change from larva to pupa 

 for mcst of the hoîometabolous insects will be a radical altering 

 in conditions of life, especially in respiration; the larva cften 

 respires through gills (many water-insects) or hâve superficial 

 respiration (parasitic Hymenoptera), while the pupae (except 

 those of Trichcptera) always hâve open spiracîes and breathe 

 atmcsphaerical air. Water-insects whcse cccoons or puparia 

 are normally found in the water will therefore always fill their 

 cocoons wit hair in which the pupa can lie. Parasitic Wasps 

 in such forms will break ou 1 : of the body of their host before 

 pupation which then takes place cutside the host when the host 

 has formed its pupal case, and then it is quite unimportant if 

 the host puparium or pupal case is submerged in or floats on 

 the water, the parasite has its air-supply for use until it has 

 moulted for the last time and escapes as imago. 



The eggs in which some little wasps, as Anagrus or Preswi- 

 chia, will develop, hâve no such air supply which can be used 

 by the parasites, in thèse instances the pupae and the not yet 

 escaped imagines must brea:he through the skin and economize 

 with the scanty content of oxygen in the egg. 



The hosts of Agriotypus, the caddis-flies, are differing from 

 the other parasite-hosts which are infested in the larval stage» 

 as the pupee are not airbreathing but use gills like the larvae. 

 Thus the Trichoptera do not procure any air-supply in their 

 pupal case, and as the pupa of Agriotypus is airbreathing and 

 thus needing air, it must itself take care of the air supply and 

 fill the cocoon with air. And the band is the means to this 

 filling. 



The pupation takes places in June — July and in autumn (at 

 any rate from Octcber) the imago is found in the host cases, 

 hibernating there. Next spring the imago escapes and the sur- 

 rounding air-bubble will take it safely to the water surface. 





