THE DIPTERA. 53 



which is very large when distended with eggs. Her general 

 colour is dull red, thus differing widely from the male 

 insect represented in the illustration (Fig. 5). 



Family 



Simulia australiensis (Plate VI., fig. I, la larva, ib pupa). 

 Every one knows the sandfly, the little black insect that 

 so persistently perches on our hands and faces and inflicts 

 its painful punctures, which in many cases are followed by 

 large swellings, often lasting for several days and causing 

 much irritation. Its larva (Fig. la) inhabits clear running 

 water, climbing about in strong currents by means of a 

 pair of suckers situated at each end of the body, two being 

 placed on the prothoracic segment just behind the head 

 and two others close to the anal extremity. These the insect 

 employs rather curiously, the anterior pair being first affixed 

 and the others drawn up close behind them, its elongate 

 body consequently forming a loop. Clinging by the 

 posterior suckers for a moment the larva then reaches 

 forward, re-affixes the anterior ones, and draws up the 

 posterior as before. Breathing is performed by two 

 spiracles situated on the last abdominal segments near 

 the hind pair of suckers. Two large air-tubes originate 

 from these and run forwards, giving off branches to all parts 

 of the body ; they terminate in a number of air-sacs in the 

 thorax. The food of this larva consists of animalculae, 

 which are no doubt obtained by drawing the two ciliated 

 appendages rapidly through the water several times in suc- 

 cession, their contents being afterwards gathered up by the 

 smaller organs and passed into the mouth. When about 

 to assume the pupa state the insect covers itself with a 

 glutinous envelope, which is firmly joined to the under side 

 of a leaf, the transformation taking place within a few 

 days. The pupa can hardly be distinguished from a 

 small moth chrysalis except for a pair of branching fila- 



