Outline of Life-history 



mud. In summer the proportion of 



ac^ a-A 



^f^ 



Rig. I.- — Larva of Chirononms dorsalis i, half- 

 grown. X 9. 2, full-grown, x 9. The numerals 

 mdicate the segments. JJ ap, prothoracic appen- 

 dages. 7't, ventral blood-gills, a.ap, anal feet. 

 a.p, anal blood-gills. In 2 the following are 

 seen through the larval skin, r./, tracheal gill 

 of pupa. I, leg. to, wing. 



saliva is greater, and 

 the tubes are lined 

 with felted fibres. 

 These summer-tubes 

 may be so coherent 

 that they can be 

 picked up with for- 

 ceps and sufier no 

 injury. The tubes 

 are, if possible, at- 

 tached to some fixed 

 object, and are often 

 much longer than the 

 body of the larva. 

 Larvae kept in a 

 clean saucer with 

 nothing but water 

 make transparent 

 tubes of saliva only. 

 In winter the larvae 

 often inhabit galle- 

 ries, whose walls have 

 little or no cohesion. 

 The larva holds on to 

 its tube, and travels 

 along it, when neces- 

 sary, by the help of 

 two pairs of limbs, 

 which are crowned 

 with circles of hook- 

 lets. One pair is just 

 behind the head, the 

 other at the tail (fig. 

 i). The limbs are 

 aided in locomotion 



