tJiat spread Disease. i 7 



mosquitoes or gnats by the absence of the long proboscis, by the 

 length of the front legs, and by their habit of resting with the front 

 legs raised — in mosquitoes it is the hind legs that are raised when 

 the insect is resting (see the models on the South side of the case). 



In the lower part of this (East) end of the case is a model of 

 the larva of Cliironomus ijlumosus, a red, caterpillar-like, aquatic 

 form sometimes termed a blood-worm. The larva lives in a 

 tunnel which it makes at the bottom of some ditch, pool or rain- 

 water butt. It breathes by means of four filaments, or blood-gills, 

 at the hind end of the body, on the last segment but one, and 

 four thicker processes on the last segment. Crawling movements 

 are effected by a pair of foot-like organs beneath the head, and a 

 pair at the hind end of the bod}'. At night, and sometimes by 

 day, the larva swims freely, jerking the body suddenly to the right 

 and to the left in such a manner as to present the appearance of a 

 figure of eight. When in its tunnel the larva imparts to its body 

 an undulating movement, thus creating a flow of fresh water 

 through the tunnel. 



The series is completed by a model, enlarged 28 times linear 

 like that of the larva and adult, of the pupa of the midge 

 Chironomus phoiiosus. While still within its tunnel the larva 

 turns into a pupa, and remains there, lying on its side and 

 imparting an undulating movement to the body. The pupa 

 breathes by means of a pair of tufted tracheal gills on the thorax. 

 When approaching the stage of the imago or perfect insect, it 

 leaves the tunnel and swims to the surface of the water ; the skin 

 splits along the back, and the winged midge emerges, and flies 

 away almost immediately. 



In the table-case that stands at the entrance to Bay I, near 

 the bust of Sir William Flower, are shown dipterous insects of 

 various kinds, tsetse-flies, tabanids and mosquitoes, selected 

 because of their capacity for spreading diseases, and mounted 

 together with examples of their near relatives, which, so far as our 

 present knowledge goes, are harmless. Since almost all insects 

 associated with maladies are of small size, the specimens are 

 mounted close to the glass of the case, in order to enable visitors 

 to see as much as possible of their general appearance and 

 external characters. The mosquitoes of this series are on the 

 West side of the case, away from the middle of the Hall. 

 Examples are shown of both males and females, and the 



c 



