Ill 



metamorphosed into pupae. I very often tried to observe the moment when the ec- 

 dysis took place, but I was always too late. Every time I found the fresh yellow 

 pupa fastened to a root, and with the two siphos pierced into the plant. At all 

 events it was now established as a fact that the pupae like the larvae are really 

 fastened to the plants using the air in the plants for respiratory purposes. 



I only wish to call attention to the almost incredible power of adaptation 

 which the Tceniorhynchns-speaes presents. Like other mosquitoes they have the re- 

 spiratory system formed in quite different ways as larvae and as pupae; as larva 

 the tracheae open in an unpaired organ, the sipho, on the eighth segment; as pupae 

 in paired siphones "trumpets" on the forepart of the body, on the cephalothorax. If 

 then the species in its two different stages as larva and pupa is to be adapted to 

 use a special source for air-supply, it is able to modify, not only the unpaired sipho 

 of the larva, but also the paired one of the pupa. One would be inclined to sup- 

 pose that the problem of making a piercing organ out of two divergent, loosely 

 attached appendices which, when used, were to act according to the new claims 

 as an unpaired organ, would have been almost insoluble even to Nature. And still 

 this problem has been solved and in the most elegant manner only by making the 

 two siphones convergent and by laying the acuminating points against each other. 

 I only regret very much that I have not been able to see how it is possible for 

 the pupa to pierce the trumpets into the plant. From our knowledge of the struc- 

 ture of the pupa-body and the different mode of locomotion it possesses I am un- 

 able to understand how it is possible for the pupa to get the necessary support, 

 which must be the condition sine qua non, if the pupa is to be able to pierce the 

 trumpets into the roots of the waterplants. Any one who will try to force a needle 

 into a root to which a Twniorhynclins-pupa is fastened, will find that this demands 

 no inconsiderable force. I have thought that the pupa might perhaps get some sup- 

 port in the larva skin, this being thrown off after the piercing process of the trum- 

 pets has been finished. But I do not possess any basis for this supposition. 



When I touched the pupa with a needle, it struck out eagerly with the ab- 

 domen; I could take the whole plant out of water, the pupa was quite unable to 

 loosen its hold. The first year all the pupae died, attacked by Mucoracece; the next 

 year three imagines were hatched, but sad to say, the ecdysis took place at a time 

 when I was at my summer laboratory; as however I found the pupa-cases floating 

 on the surface and the hooks of the siphos broken off, there can be no doubt that 

 the pupae, when the ecdysis is going to take place throw themselves away from 

 the plants by means of the abdomen and rise to the surface. This is also in ac- 

 cordance with some observations made by Edwards just published (1919 p. 83). 

 Although he has not found a living pupa, he is able to record that several speci- 

 mens of T. Richardi were hatched in a pail which he had brought home full of 

 pond water and sods of grass. "The empty pupul skins were found floating on the 

 surface for the emergence of the adult. An examination of these skins showed that 

 in every case the terminal portions of the breathing-tubes were missing; hence it 



