226 



HARDWICKE'S SCIENCE- GOSSIP. 



[Oct. 1, 1867. 



are drawn up beneath its breast, since our fiend of 

 the air is a poor pedestrian. 



Its gleaming wings are, however, beautiful objects. 

 They form a broad expanse of delicate parchment- 

 like membrane drawn over an intricate network of 

 veins. Though the body is bulky, it is jet light, 

 and [easily sustained by the wings. The long tail 

 undoubtedly acts as a rudder to steady its flight. 



These insects are almost universally dressed in 

 the gayest colours. The body is variously banded 

 with rich shades of blue, green, and yellow, and the 

 wings give off the most beautiful iridescent and 

 metallic reflections. 



During August, the various species of Libellula 

 and its allies most abound. The eggs are attached 

 loosely in bunches to the stems of rushes and other 

 water-plants. In laying them, the Dragon-fly, 

 according to Mr. P. E. Uhler's observations, 

 "alights upon water-plants, and, pushing the end 

 of her body below the surface of the water, glues 

 a bunch of eggs to the submerged stem or leaf. 

 Libellula auripennis I have often seen laying eggs, 

 and I think I was not deceived in my observation 

 that -she dropped a bunch of eggs into the open 

 ditch while balancing herself just a little way above 

 the surface of the water. I have, also, seen her 

 settled upon the reeds in brackish water with her 

 abdomen submerged in part, and there attaching a 

 cluster of eggs. I feel pretty sure that Libellula 

 auripennis does not always deposit the whole of 

 her eggs at one time, as I have seen her attach a 

 cluster of not more than a dozen small yellow eggs. 

 There must be more than one hundred eggs in one 

 of the large bunches. The eggs of some of the 

 Agrions are bright apple-green, but I cannot be 

 sure that I have ever seen them in the very act of 

 oviposition. They have curious habits of settling 

 upon leaves and grass growing in the water, and 

 often allow their abdomens to fall below the surface 

 of the water ; sometimes they fly against the sur- 

 face, but I never saw what I could assert to be the 

 projecting of the eggs from the body upon plants or 

 into the water. The English entomologists assert 

 that the female Agrion goes below the surface to a 

 depth of several inches to deposit eggs upon the 

 submerged stems of plants." The Agrions, how- 

 ever, according to Lucaze Duthiers, a French ana- 

 tomist, make, with the ovipositor, a little notch in 

 the plant upon which they lay their eggs. 



These eggs soon hatch, probably during the heat 

 of summer. The larva is very active in its habits, 

 being provided with six legs, attached to the thorax, 

 on the back of which are the little wing-pads, or 

 rudimentary wings. The large head is provided 

 with enormous eyes, while a pair of simple, minute 

 eyelets (ocelli) are placed near the origin of the 

 small bristle-like feelers, or antennas. Seen from 

 beneath, instead of the formidable array of jaws and 

 accessory organs commonly observed in most carni- 



vorous larvae, we see nothing but a broad, smooth 

 mask covering the lower part of the face, as if from 

 sheer modesty our young Dragon-fly was endeavour- 

 ing to conceal a gape. But wait a moment. Some 

 unwary insect comes within striking distance. The 

 battery of jaws is unmasked, and opens upon the 

 victim. This mask is peculiar to the young, or 

 larva and pupa of the Dragon-fly. It is the labium, 

 or under lip greatly enlarged, and armed at the 

 broad spoon-shaped extremity with two sharp hooks, 

 adapted for seizing and retaining its prey. At rest, 

 the terminal half is so bent up as to conceal the face, 

 and thus the creature crawls about, to all appear- 

 ance, the most innocent and lamb-like of insects. 



Not only does the immature Dragon-fly walk over 

 the bottom of the pool or stream it inhabits, but it 

 can also leap for a considerable distance, and by a 

 most curious contrivance. By a syringe-like appar- 

 atus lodged in the end of the body, it discharges a 

 stream of water for a distance of two or three inches 

 behind it, thus propelling the insect forwards. This 

 apparatus combines the functions of locomotion and 

 respiration. There are, as usual, two breathing 

 pores (stigmata) on each side of the thorax. But 

 the process of breathing seems to be mostly carried 

 on in the tail. The tracheae are here collected hi a 

 large mass, sending their branches into folds of mem- 

 brane lining the end of the alimentary canal, and 

 which act like a piston to force out the water. The 

 entrance to the canal is protected by three or five 

 triangular horny valves, which open and shut at will. 

 When open, the water flows in, bathing the internal 

 gill-like organs/which extract the air from the water. 

 This is then suddenly expelled by a strong muscular 

 effort. 



In the smaller genera, Agrion, Lestes, and Calop- 

 teryx, the respiratory leaves, called the tracheary, 

 or false-gills, are not inclosed within the body, but 

 form three broad leaves, permeated by tracheae, or 

 air-vessels. They are not true gills, however, as the 

 blood is not aerated in them. They only absorb air 

 to supply the tracheae, which aerate the blood only 

 within the general cavity of the body. These false-gills 

 also act as a rudder to aid the insect in swimming. 



It is easy to watch the Dragon-flies through their 

 transformations, as they can easily be kept in 

 aquaria. Little, almost nothing, is known regarding 

 their habits, and any one who can spend the neces- 

 sary time and patience in rearing them, so as to 

 trace up the different stages from the larva to the 

 adult fly, and describe and figure them accurately, 

 will do good service to science. 



Mr. Uhler states that at present we know but 

 little of the young stages of our species, but " the 

 larva and pupa of the Libellulidae may be always 

 known from the iEschnidae by the shorter, deeper, 

 and more robust form, and generally by their thick 

 clothing of hair." 



The pupa scarcely differs from the larva, except 



