12 NEW ZEALAND NEUliOPTEEA. 



attack one another. De Selys found that from a pond 

 filled with carp, roach, perch, and eels, several of the 

 dragon-fly denizens disappeared directly the bream was 

 introduced. On the other hand, there can be little doubt 

 that the nymphs are sometimes injurious to fish ; it has 

 been recorded that in a piscicultural establishment in 

 Hungary 50,000 young fishes were put into a pond 

 in spring ; in the following autumn only fifty-four fish 

 could be found, but there were present an enormous 

 quantity of dragon-fly nymphs.* 



It has been observed that certain European species of 

 dragon-flies form swarms and migrate ; it will therefore 

 be of interest to ascertain if the migratory instinct exists 

 in any of our New Zealand species. In past years I have 

 noticed swarms, but not distinct migrations. Of late all 

 our dragon-flies appear much scarcer than in former times, 

 though this apparent decline in numbers may be due to 

 temporary causes only. 



The fossil remains of a huge dragon-fly have been 

 discovered in the carboniferous strata at Commentry. 

 From the restoration which has been made of this giant 

 it would appear to have measured over two feet across 

 the expanded wings. 



Sub-Family I.— ANISOPTERIDES. 



Dragon-flies having the hinder wings slightly larger than the anterior 

 pair. 



Tribe LIBELLULINA. 



" Eyes large and contiguous, without any tubercle behind. The first 

 ante-nodal nervule of the fore-wings is not always continuous across the 

 lower costal space; the hind-wings are rounded at the anal angle in both 

 sexes ; the triangles of the fore- and hind-wing differ in shape ; sectors of 

 the arculus united at the base. 



Genus SYMPETEUM, Newman (1855). 



" Frontal tubercle slightly truncate ; posterior lobe of the prothorax 

 elevated. Pterostigma generally short or moderate ; sectors of the arculus 

 petiolate ; one cross-nervule in the lower basal or median space. Fore-wings 

 •with 7 or 8 (rarely 9 or 10) ante-nodal and or 7 post-nodal nervules, the 

 last ante-nodal very rarely and the first two or three post-nodals never con- 

 tinuous across the lower costal space ; triangle rather broad, free, on a level 



Sharp, loc cit. 425. 



