THE BIONOMICS OF AUSTRALIAN TABANIDAE. 49 



As the larvae reached maturity and ceased to feed (about the third week in April) 

 they were placed together again in a large receptacle containing moist sand, in which 

 they jemained for about two months. At first they were very active, coming 

 to the surface at night and returning to the sand during the day, but never attacking 

 each other. On 3rd June they were all in a torpid state and contracted to about 

 18 mm. in length, but when placed in water they regained their normal appearance 

 and activity. 



On 25th June one of the larvae, now 164 days old, pupated in a vertical position 

 four inches below the surface and after a pupal period of 11 days emerged as a perfect 

 fly (female). Another larva pupated about a week later and was preserved as a 

 specimen ; the third pupated on the 7th July and produced a male fly on 21st July, 

 or 190 days after hatching ; the fourth remained in the larval stage until 8th 

 September (239 days), when it was destroyed for examination. 



Larval Habits under Natural Conditions. Under natural conditions the larvae are 

 to be found commonly on or near the surface of clear and moderately deep pools, 

 amongst submerged herbage near the banks, resting upon the lower surface of lily 

 leaves, upon the submerged stems and leaves of all kinds of aquatic plants and in 

 floating masses of algae. Clear and moderately deep water appears to be essential. 

 The food of the young larvae is not known, but it is beHeved to be the small molluscs, 

 which were fed successfully to larvae reared in captivity. Several kinds of molluscs 

 are very plentiful in most of the breeding-places, and these certainly form an important 

 part of the diet of older larvae, which have frequently been found feeding on them. 



In the rock-hole (Locality 1) this food is absent, but there is a plentiful supply of 

 other kinds. Cannibalism is common amongst " wild " larvae, and is practised by 

 individuals in all stages of development. To give some idea of the voracy of these 

 insects, it may be mentioned that on one occasion 12 large larvae were placed in a 

 pickle-jar of water and algae for transportation to the laboratory — a journey of 

 three miles — and upon arrival there only two remained alive, one of which destro3'ed 

 the other before arrangements could be made for their separate accommodation. 

 On another occasion over 50 nearly full-grown larvae were placed in a large 

 porcelain dish with sand, water and fresh molluscs. Within four daj's many of 

 the latter and 40 of the larvae were destroyed. 



With the aid of a small stout wire net attached to the end of a long bamboo rod 

 the plant growth can be disturbed sufficiently to dislodge the larvae, which, even if 

 carried down by the cuiTents thus created, soon appear near the surface and are easily 

 captured in the net. In some cases a stout wire hook at the other end of the rod was 

 found useful for dragging masses of vegetation towards the bank for closer inspection. 

 W^ading was resorted to in many cases, but the results were usually unsatisfactory on 

 account of the restricted range of vision. 



The larvae appear to live entirely in water until they have reached maturity, 

 when they migrate from the water to high ground close by, as described elsewhere in 

 this paper, and penetrate into the soil or clay to a depth of from 7-15 cm., where they 

 remain in the larval stage, generally with head uppermost, for several months. 



The Pupa. During the first few hours following metamorphosis the entire pupa 

 is buckthorn-brown,* but the e^^es soon deepen to mummy-brown, and then to blackish 

 brown, while the thorax becomes argus-brown. The average size is about 21 mm. in 

 length by 4 mm. in width at the thorax, the 1st and 6th segments slightly narrower 

 than the 2nd to 5th inclusive. 



On the dorsal surface of the first abdominal segment there are two stout hairs on 

 either side of the median line and three on each pleura, two of which arise close 

 together near the wing-sheaths. Segments 2 to 7, inclusive of both surfaces, bear an 



* Ridgway's colour nomenclature. 

 (2416) D 



