596 ON THE GENUS DIPHLEBIA, 



SO that the larvae could only crawl slowly and helplessly along, 

 trying always, like an iguana, to get on the side of the rock away 

 from me. I tried several times to see how they behaved under 

 water. To do this, I took a rock to which a larva was clinging, 

 and lowered it gently into the water, watching the larva care- 

 fully. I found that, under water, they could move with more 

 rapidity, l)ut I was easily aWle to follow them with my hand, and 

 catch them again merely by feeling for them. Occasionally one 

 got detached from a stone, when it would spread out its legs and 

 caudal gills, and rock itself slowly to and fro, gradually sinking 

 the while. These observations satisfied me that the larva was 

 purely a rock-liver, and that, once detached from its refuge, it 

 was a hopelessly clumsy creature. As was evident from the form 

 of the legs and abdomen even in the exuvije, the whole insect is 

 built so as to be able to cling flatly and closely to the rock-surface, 

 where it is able to lie concealed, and capture its prey in the 

 running water. 



The emergence of D. nymphdides is very similar to that of 

 Atistrogomphjis heteroelitus, a species which was emerging in 

 great numbers on the same creek. Both larvae climb up the 

 rocks, just above water-level, and emerge there, only the Diphlebia 

 prefers the vertical or overhanging surfaces, facing down-stream, 

 so as to be away from the current; while the Austrogomphus 

 usually chooses a more slanting surface, often on the up-stream 

 side, so that it gets washed by the little wavelets and ripples, and 

 is thus apparently helped upwards along the rock The newly 

 emerged insects, in both cases, rest only just out of reach of the 

 water, and fly straight off into the bush as soon as their wings 

 are dry enough. 



Three of the larvai which I took, emerged during the following 

 week. They were placed in wide-mouthed bottles half-filled with 

 water, and with sticks to climb up Two of them emerged with 

 the exuviae partly under the water; the third climbed about two 

 inches al)ove the water. All three were females. This leads me 

 to believe that the males emerge considerably earlier, on the 

 whole, than the females; and certainly their colouration, at the 

 date of my visit, suggested that they were the mure mature. 



