13 



numbers are implanted between these tufts; the posterior tuft is best developed and 

 always feathered, but all in all the place and the development of these hair-tufts are so 

 constant that they cannot be used as characters for classification. A peculiar structure 

 is the lateral groups of spines or scales; these scales are either arranged in a single 

 line, as is the case with Finlaya geniculata and Tceniorhynchus, often, but not always, 

 with A. cinereus, or in irregular arched series, covering a triangular spot on the sides 

 of the eighth segment; the largest number of scales is always in the anterior rows. 

 The number of scales is very different in the species, but fairly constant in the same. 

 It is only about from ten to twelwe in F. geniculata, Tazniorhynchus Richardi; com- 

 monly from twenty to forty in most of the Danish species of the genus Ochlerotatus, 

 but about one hundred in C. morsitans; it seems as if the number is greatest in 

 those species which have the longest siphones and the best development of the 

 flabellae. The base of the scales is always spatulated ; they are often provided with 

 one strong spine, two shorter laterally, and many shorter ones bordering the sides 

 of the spatulated part; they may also as in some of the species of Ochlerotatus be 

 broad plates, ending in from five to seven thorn-like prolongations of equal length. 

 They are often laterally covered with a delicate, hyaline membrane, radiated along 

 the borders. Their number, position and form are of great value as characters for 

 classification; in the systematical descriptions they are determined as the comb. The 

 significance of the comb for the animal is in my opinion quite enigmatical. The 

 median spines of the scales may be rather long and very acute; still it is rather 

 difficult to understand, how they can be a weapon for the larvae; where there are 

 many scales, the comb impresses me as a carding apparatus, but I am unable to see, 

 how the animal should use such an organ. 



Dorsally the eighth segment carries one of the most interesting organs of the 

 Culicin larvae, the sipho; this is always strongly chitinized, of a dark brown or 

 yellow colour; nearest to the base it has almost always a strong chitinized black 

 ring. If we compare Tab. XIX of C. morsitans with Tab. II of C. caspius we shall 

 see the great difference with regard to the dimensions even in a fauna so small as 

 the Danish one. It is commonly about three times longer than broad but may, as 

 is the case of C. morsitans, C. pipiens and C. nigritulus, be from five to seven times 

 longer than broad; it is extremely short, almost inflated, in 0. caspius. At the apex 

 we find an opening through which the larva takes air into its tracheae. The sipho 

 is closed by a set of five flaps ; when the larva comes up to the surface, the flaps pierce 

 the surface of the water; then they are folded out and pressed against it; by means 

 of the surface film the larvae hang down from the surface and draw the air into 

 the tracheae. When I have had different species isolated in vessels and have exam- 

 ined the surface, from which the larvae were hanging, with the binoculary aquarium 

 microscope I got the impression that the stars which the five flaps formed upon 

 the surface had quite a different aspect in the different species. The form of 

 the flaps and their bristles differ from species to species; but this can only be 

 thoroughly studied when the larvae are killed with the flaps open, the sipho cut 



