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No one can observe a mosquito pupa without being struck by the peculiar 

 disproportion between the bulky cephalo-thorax mass and the slender abdomen; it 

 is upon this incongruity that the peculiar somersault motion depends. When the ec- 

 dysis is going to take place, the thorax splits in the middle line, the large sides of 

 the chephalo-thorax are clapped downwards and now rest upon the surface of. the 

 water; they thus form a swimming point of support upon which the imago may 

 rest during the ecclosion and a few minutes immediately after. The actual process 

 of ecclosion of the imago \vill not be mentioned here; with regard to that point I 

 refer to the excellent paper by EYSELL (1913 p. 320). 



In the above I have tried to elucidate some points in the biology and anatomy of 

 the mosquito pupa. Its many peculiar anatomical structures: its highly remarkable 

 form, the air-globules below r the wing-sheaths, the use of the tips of the trumpets as 

 points of support, the stellate hairs, combined with the short life-time of the stage 

 and the peculiar manner of motion may all be regarded as adaptations directed 

 towards the same great general end : to bring the imago as soon as possible and in dry 

 condition out of the water. The common significance of the pupa stage of insects : that 

 of being a stage of repose, has in the pupa stage of the mosquitoes been subordinated 

 to this purpose; it is the life as free-swimming organisms exposed to dangers of 

 every kind, very different from the common pupa life of insects, which has made 

 this subordination necessary. It is often very difficult to distinguish the species from 

 each other in those immature stages which have the shortest existence. In the 

 development of the mosquitoes the pupa-stage, as is the case with other insects, is 

 the shortest. It is a well-know r n fact that it is almost quite impossible to distinguish 

 the species in this stage; even species which belong to different subfamilies: Ano- 

 phelines and Culicines, are extremely alike in the pupa stage. This has also been 

 pointed out by HOWARD, DYAR and KNAB (1912 p. 103). These authors remark that 

 there really are some striking differences between the pupae, of the two tribes Culi- 

 cini and Sabethini; further, that there are some differences in the shape and length 

 of the trumpets and of the paddles. The greatest diversity may probably be found 

 in the number and arrangement of the setse on different parts of the body; by 

 this structure MEIJERE (1911 p. 1146) has tried to distinguish the pupa? of C. morsitans, 

 Theobaldi, C. cantans and communis but, as far as I can see, without any result. I 

 have been unable to detect real differences between the pupae of the Danish species. 

 The very large pupae of C. annulatus and C. morsitans can, if they appear in the 

 swarms of C. communis, be distinguished only by their size. With regard to the 

 pupae of Tceniorhynchus I refer the reader to that genus. 



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