SCIENCE-GOSSIP. 



149 



require a week or two before the appearance of 

 substitutes. In passing, I may say that the 

 phenomenon is apparently confined amongst the 

 dragon-flies to the members of this sub-family. 



M. pumilio. — This nymph resembles the preced- 

 ing. The head has tubercles, seen also in the 

 adult ; the fore-margin of the mask is wavy, and 

 on the main portion there are but six hairs 





Larv.-e-Nymphs of Agrionin<e. 



Fig. 16 represents (a) the head, antennae, thorax, wing-sheaths and legs, (6) the final abdominal segment and caudse, 

 and (c) right half of "mask," with mandible, of Agrion Virgo. Fig. 17 represents A. splendens. Fig. iS is of Platycncmis 

 pennipes : a, mandible ; 6, caudal lamella; and c, antennae. Fig. 19, Lestes oarBara ; 1917, mandible. Fig. 20. L. virens ; 20a, 

 mandible. Fig. 21, L. viridh ; am, mandible. Fig. 22, Micronympha efcgans: 11a, mandible ; 226, caudal lamella. Fig. 23, 

 details ot M. pumilio: a, mandible; 6, caudal lamella; c, antennae ; d, leg, showing metacarpus; 1, 2, 3, metacarpal spines. 

 Fig. 24 : a, mandible ; and b, caudal lamella and portion of final segment of Canagrion puella. Fig. 25, corresponding parts of 

 Erythromma viridulum. 



Fig. ioc is the corrected drawing of the anal appendages of Bmchytron pratetise, the former figure (Science-Gossip, p. 131) 



being incorrectly rendered. 



