148 



SCIENCE-GOSSIP. 



LARV^-NYMPHS OF BRITISH DRAGON-FLIES. 



By W. H. Nunney. 

 (Continued from page 131.) 

 Until quite recently tinuous line on each side of the body. In some 



JDYRRHOSOMA minium 



the larva-nymph of this species was, I 

 believe, entirely unknown. I was fortunately able 

 to rear the imago during May, 1894, from larvae 

 taken at Wanstead, in September, 1893. Of eight 

 larvae two only lived till the time for the final 

 change. One of these, from its weakly condition, 

 failed to develop. The remaining nymph developed 

 into a female imago of this species. Even the 

 survivor had lost all three of its caudae. Notwith- 

 standing this the usual abdominal appendages are 

 present in the imago in a somewhat modified form, 

 they being shorter and broader at the base than is 

 usual, and the external margins form an almost 

 equilateral triangle. I now possess several nymphs 

 in spirit, a cast skin, and the newly-emerged female 

 imago. The larva-nymph is synthetic, having 

 many points in common both with the species of 

 Micronympha and Ccenagrion puella, the especial 

 points of resemblance being the possession of 

 metacarpal spines, as in Micvonympha, and the form 

 of the mask, which differs but little from that in 

 C. puella. The accompanying figures should be 

 compared. This species is dark brown, paler 

 below ; the legs, antennae and caudae lighter. The 

 latter are thickly blotched with dark brown. The 

 femorae and tibiae are spotted. The head is rugose, 

 sparsely haired, and is not nearly so quadrate in 

 form as in Micronympha, and the hinder angles are 

 furnished with characteristic tubercles (see fig. 26). 

 Two small depressions occur in front of the 

 antennae. There are two dark lines on the nasus, 

 some pale spots on the disk, and three pale curved 

 lines on the occiput. 



The abdomen has very minute pale spots on the 

 hinder margin of each segment, except the final. 

 The ninth has two small recurved hooks below, 

 and the lower margin of the final segment is 

 furnished with small points. Upon the entire 

 margin of this segment there are many small 

 incurved spines. The caudal lamellae are much 

 spotted, especially at the apex, and the underside 

 is almost entirely hairy. The central vein is 

 strong, prominent and much thickened basally. 

 The metacarpus is furnished with characteristic 

 scales of a slightly different form to those similarly 

 occurring in Micronympha . The tarsi are slightly 

 hairy on the underside. 



About four months after the capture of these 

 nymphae the pale hind-marginal spots became 

 almost obsolete, and a whitish line upon each 

 segment laterally became visible. Without close 

 examination this has the appearance of a con- 



specimens the lines extend to the underside of 

 the thorax. 



MICRONYMPHA elegans, usually greenish- 

 yellow, varies greatly in colour, that of the head 

 and eyes changing according to the creature's age. 

 Two fasciae occur around the basal tubercles of 

 the antennae ; two curved lines converge towards 

 the tubercles of the ocelli, and two other curved 

 lines occur on the hind borders of the head, tending 

 medially towards the other lines, from which they 

 are divided by a small straight line crosswise in 

 the centre of the curved hinder margin ; on the 

 fore-face are two slight depressions usually filled 

 with dirt-particles, consequently difficult to see. 

 The body has, on all but the final segments, four 

 curved lines arranged thus, ) ( ) ( • Peculiar spines 

 (shown in fig. 23) occur on the metacarpus ; to see 

 these a microscope is necessary. The caudae are 

 ovoid, spined along the basal upper margins, and 

 are slightly notched where the spines end. The 

 central tracheal stem is thickened and is crossed at 

 the marginal notch by an additional thickening. 

 According to Roster, the apical angles alter with 

 the age of the nymph. This species is fairly 

 common in small streams, ponds and weedy 

 irrigation ditches, but is somewhat local. During 

 the first week of July, 1893, a female larva of this 

 species, taken at Epping Forest, lost the two 

 hinder legs on the right side, stumps only remain- 

 ing. Thinking that upon undergoing its final 

 metamorphosis the creature would be still devoid 

 of these particular limbs, I isolated the specimen. 

 On the 10th and nth of July the larva underwent 

 a moult. On examining the larva after, through a 

 lens, I was greatly surprised to see that the lost 

 members were renewed, they being, however, some- 

 what more slender than their predecessors and 

 wanting the tarsal claws and femoral spots. The 

 reproduction of lost legs, though a common enough 

 occurrence amongst crustaceans and some other 

 groups, is apparently extraordinary in this con- 

 nection, notwithstanding the occasional renewal of 

 lost caudal lamellae. In this instance the repe- 

 titional process was very remarkable, inasmuch as 

 the lost limbs were not replaced by the slow and 

 gradual growth during many days usually ac- 

 companying this phenomenon, but were reproduced 

 almost spontaneously, or, at any rate, between 

 midnight on the 10th of July and eight o'clock on 

 the following morning, the whole development 

 being thus compressed into but a few hours at 

 most. Lost caudal lamellae, so far as I am aware, 



