The South Australian Naturalist. 



The Rat -tailed Maggot (fig. 5a), the aquatic larva of a fly 

 {Erhtalis tenax), will be found in foul water. It breathes 

 through a long flexible tube at the end of its bod}' ; to allow for 



descent to varying depths in thi^ fluid in which the maggot lives, 

 this organ is telescopic, and its length is thus adjusted as occasion 

 demands. The tip is furnished with five little tufts of hair, which 

 rest on the surface film, so that the spiracles are in contact with 

 the air. The insect leaves the water to pupate, and while in the 

 chrysalis form breathes through two tubes near the front of the 

 eocoon (fig. 5b). After emergence, the Drone-fly hovers over 

 flowers, thus finally attaining to surroundings very different from 

 the often filthy situation of its larva. 



The larva of our common Grey Mosquito ( Culex fatigans) 

 is yet another example of an aquatic insect which breathes 

 through a pipe at the posterior end of the body, aud its siphon 

 is a marvel of ingenuity. It has been shown that the surface 

 film offers a considerable resistance; how then does such a tiny 

 creature overcome this elastic barrier to the air, which is essential 

 to its existence? The orifice of the respiratory tube is only 

 opened when the insect comes to the surface, and is closed at will 

 with five or six little flaps, a mechanism which prevents water 

 from penetrating the air passages. When closed, the tube is 

 jsharp and pointed, and is thus easily pushed through the surface 

 film ; the flaps then open out in the form of a cup, which floats 

 and enables the larva to remain ^suspended head downwards. 

 Four tracheal gills are also present on the last abdominal seg- 

 ment, but as this larva almost continually breathes atmospheric 

 air through its respiratory siphon, such appendages are small. 

 Ijarvae of some mosquitoes have Avell-developed tracheal gills, 

 and remain completely submerged for long periods. Long hairs 

 protect the vent and aid in swimming. 



In the chrysalis stage, which is also spent in the water, the 

 insect obtains air through two little funnels situated on the back 

 of the pupa case. Two paddles at the termination of the 

 abdomen enable the active pupa to dart away with a eharacteristii^ 

 tumbling motion. 



Members of the family Ckirononiidae somewhat resemble 

 mosquitoes, but lack a sucking proboscis. The larvae are known 

 as Blood-worms, owing to their brilliant red colouring. This 

 tppearance is due to the presence of haemoglobin, a matter 

 capable of absorbing oxygen. The tracheal system is rudiment- 

 ary, and as gas is held by the haemoglobin, the Blood-worm has 

 no need to frequently ascend to the surface. 



