148 NATURAL HISTORY OF AQUATIC INSECTS cil 



and then returns in as many reversed and overlapping 

 loops, so as to give the appearance of a lock-stitch. 

 The thread is so tough that it can be drawn out 

 straight with a needle without breaking. If the egg- 

 rope is dipped into boiling water, the threads become 

 apparent, but in the natural state they are invisible, 

 owing to their transparency. The mucilage is held 

 together by the threads interwoven with it. The 

 loops can be straightened without injury until the 

 length of the rope is almost doubled. If stretched 

 beyond this point the threads become strained, and 

 do not recover their original shape when released. 

 By means of these threads the whole mass of many 

 hundreds of eggs is firmly moored, yet so moored that 

 it floats without strain, and rises or falls with the 

 stream. The eggs get all the sun and air which they 

 require, and neither predatory Insects, nor Birds, nor 

 water-moulds, nor rushing currents of water can 

 injure them. All the species of Chironomus arc not 

 alike in the formation of their egg-chains. See for 

 example Fig. 44. 



It is always interesting to the biologist to find the 

 same contrivance made use of by animals of different 

 kinds, and I have therefore thought it worth while to 

 mention a number of other animals which coat their 

 eggs with jelly. 



Insects yield many examples. One of the most 

 familiar is furnished by the Caddis-flies. Sometimes 

 (Mystacides) they lay their eggs in a roundish 

 gelatinous disc, a quarter of an inch across, which is 

 attached to an aquatic leaf, and contains hundreds of 

 eggs arranged within it in a regular spiral line. Some- 



