42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



to enclose a large air cavity, but on pressing a pupa in alcohol the air 

 issues as free bubbles from beneath the legs and wings. 



The pupa has two features that are peculiarly its own. First are 

 the trumpet-shaped respiratory tubes projecting from the back of 

 the thorax (fig. 16C, Tmp), and second, a pair of thin, oval fan- 

 shaped tail fins, or paddles, borne on the end of the abdomen (A, tf). 

 Because it is necessary for the pupa to float with the back of its 

 thorax against the surface of the water, with the abdomen hanging 

 down, it had to discard the posterior spiracles of the larva and have 

 its breathing apertures forward. The trumpets are connected with 

 the anterior ends of the dorsal longitudinal tracheal trunks, and their 

 open ends project just above the surface of the water. 



It is a curious fact that in species of Mansonia and Ficalbia, the 

 larva of which gets its respiratory air from the roots of aquatic plants, 

 the pupa does the same thing by means of its thoracic trumpets. The 

 trumpets in these species are drawn out into a pair of long horns 

 directed forward from the thorax. In Ficalbia hybrida each horn 

 ends in a pair of tapering blades (fig. n F), but in species of Man- 

 sonia each terminates with a strong, curved spine. The spines of 

 Mansonia richiardii (E) are convergent and are said to be applied 

 close against each other as inserted into the plant. In the species shown 

 at C of the figure the spines are divergent, and, as in other species, 

 each is bordered anteriorly and posteriorly (D) by a very thin, trans- 

 parent, faintly striated flange. A trachea (C,E, Tra) is attached to 

 the base of the organ, but does not penetrate the latter. The cylindrical 

 basal stalk contains a wide lumen, which narrows abruptly where it 

 enters the spine and opens by a minute aperture at the tip. Wesenberg- 

 Lund (1920-21), however, says of M. richiardii that "the trachea runs 

 through the whole tube," and Grossbeck (1908) figures a tube of 

 Culex perturbans with a trachea going through it to the tip of the 

 spine. It seems very unlikely, however, that the thoracic respiratory 

 tubes in any case contain tracheae. They are merely elongated trum- 

 pets, and a typical trumpet is an open funnel with the trachea opening 

 into its base (fig. 17 C, Tra). 



As the pupa of Mansonia emerges from the larval skin, according 

 to Galliard (1934) as quoted by Marshall (1938), it brings the tips 

 of its horns together and searches for a neighboring root. Then it 

 violently works its way out of the anchored larval skin and at the 

 same time inserts its horns. When the adult is ready to emerge, the 

 pupa breaks away from the plant and comes to the surface where it 

 floats by reason of two tracheal air sacs in the thorax. The winged 

 mosquito thus escapes into the air in the usual manner. 



