18 



the other larvae, I saw that this supposition was probably wrong. - - Most probably 

 the flabellae have yet a third function; they certainly play a prominent role as organs 

 which contribute to the renovation of water in in the neighbourhood of the larva. 



The structure of the mandibles is rather complicated; they are well described 

 by some earlier authors, especially HOWARD, DYAR and KNAB, but the use made 

 of them is not clearly understood. They are almost hidden by the large, very broad 

 maxillae. The dorsal (inner) margin of the mandibles bears a system of thorns, setae, 

 and strong chitinised teeth, the arrangement of which is common to all mosquito 

 larvae. - - Nearest to the outer angle some strong movable spines are inserted; the 

 number (from two to four) of these spines varies from species to species; the inner 

 margin is further equipped with a series of tubercles carrying thorns in very different 

 states of development in the different species; these thorns are badly developed or 

 almost absent in those species which find their food in the water layers, but strongly 

 developed in those which mainly brush off the food from a substratum. In T. annulata 

 the spines are comb-like with very long, curved teeth. On the inner side of the 

 mandibles, parallel with the inner margin, an elegant fringe of long, soft hairs is 

 inserted; they take their rise from a crescentic chitinous ridge; every hair in this 

 fringe is kneed, and all always at the same distance from the crescentic ridge; 

 therefore the whole fringe is kneed; also in the development of this fringe there is 

 great difference in the different species; it is always largest in those species which 

 only live upon suspended material; it may further be added, that the hairs in the 

 fringe are much stronger, almost thorn-like, in those which live upon sedimented 

 bottom material. The apices of the mandibles facing each other bear a number of 

 dark, strongly chitinised teeth, and in front of them commonly a long, movable 

 often dentated tooth; this part of the mandible varies from species to species; it 

 is always chitinised, most strongly in the species living upon sedimented bottom 

 material. Below the teeth we find a peculiarly shaped single or double fork-like lobe, 

 with two constant hair-brushes Between this lobe and the dark chitin teeth a series 

 of hairs is inserted; these hairs are thorn-like in the bottom feeders. The three 

 above-named parts: the strong spines on the outer angle, the fringe, and the chitin 

 teeth below, play quite a different role in the act of feeding. Under the bino- 

 culary aquarium microscope it is easy to see, that the mandibles, whenever the 

 flabellae are folded together, with the above-named two or four spines on the outer 

 angle are struck into the hair-brushes; when refolded, the hairs pass between the 

 spines, acting as teeth between which the hairs are combed free from adherent 

 particles. At the moment when the fiabellae are struck inwards, and the whole 

 organ folded together, the mandibles meet each other in the middle line, and the 

 above-named thorns form the combing apparatus; when removed the mandibles 

 are thrown outwards. 



The function of the fringe is most probably partly to bound the space in 

 which the particles are swept down, partly to brush them downwards into the 

 masticatory part of the mandible, the short sharp chitinous teeth between which 



