322 BIONOMICS, ETC. [CH. 



and jungle, while those with brilliantly coloured wings fly up 

 and down the rivers. 



Most of the Lestidae and Agrionidae congregate close to the 

 banks of rivers, lakes or ponds. They tend to form "colonies"; 

 i.e. a species may be very abundant on one pond, or along a certain 

 stretch of river, but absent from another near by. Many of these 

 colonies may be due to the phenomenal success of the progeny 

 of a single pair, or of a few pairs, which visited the locality for 

 ovipositing in a previous year. Besides these brightly coloured 

 little gems, the most sun-loving of all the Dragonflies are the 

 Libellulidae and the genus Anax. 



The differences in flight are very great, both in style and in 

 speed. The Zygoptera on the whole use their wings in the manner 

 known as "sculling," their passage over the water close to the 

 surface no doubt suggesting this metaphor. Amongst the 

 Aeschnidae in general, a "darting" method of flight is very 

 evident, the insect progressing by a series of jerks. This is varied, 

 in the larger Aeschninae, by "hawking," a term which indicates 

 a strong steady flight up and down some particular "beat," with 

 a view to driving off all other intruders, and securing all the food 

 to be found. In the Libellulidae, we miss the jerking movement 

 as well as the power of the Aeschnine-fiight, which is, in most 

 cases, replaced by a "skimming" or "soaring" mode of flight. 

 The Trameini, which have the broadest hind- wings of all, float 

 airily about with very little effort. Some of the smaller Libellulidae 

 develop a great power of " dodging." The Sympetrini foil attempts 

 at capture by short darts forward, sideways, or even backwards 

 behind one's net. Cordulephya and the Tetrathemini perform 

 zigzag spirals up into the air in the most tantalizing manner. 

 For perfection of evolutions during flight, the Eucorduliini must 

 be given first place. Many of these can fly backwards for short 

 distances ! 



As regards speed, many Dragonflies are notoriously swift. 

 Estimates of the speed of a small object are very apt to go astray. 

 Of the genera known to me, Macromia and Austrophlebia are 

 by far the swiftest on the wing. As the latter flies regularly up 

 and down small mountain streams, I had an opportunity once 

 of timing it over a measured stretch of between eighty and ninety 



