70 NATURAL HISTORY OF AQUATIC INSECTS CH. 



free the legs for fear of breaking them off. The 

 head was still entirely enclosed in the larval integu- 

 ment, and this was so hard that I had great diffi- 

 culty in removing it. I succeeded, however, without 

 wounding the pupa, but the head, being too tightly 

 packed in the corresponding part of the larva, had 

 not assumed its natural form, and instead of being 

 bent upon the thorax was stretched out. Moreover, 

 the legs, some of the tips of which I had broken off 

 in trying to free them from the larval skin, had taken 

 neither the form nor the arrangement suitable to the 

 pupa. Hence this Insect also was unable to complete 

 its transformation. 



" The difficulties which I had encountered in pro- 

 curing healthy pupae made me suspect that I had not 

 given them earth sufficiently damp, and that the skin 

 of the larva must be slightly moistened in order that 

 the parts of the pupa may free themselves without 

 injury. I therefore took a larva which had been 

 wandering for fifteen days here and there on the 

 ground without offering to enter it. I placed it in a 

 large leaden box filled with earth much damper than 

 before. The larva entered the earth, and some days 

 after changed to a well-formed white pupa. On each 

 side of the head (on the fore part of the prothorax) 

 were three brown strong hooks. Two others of the 

 same kind were found at the hinder end of' the body. 

 These hooks being solid can contain no part of the 

 perfect Insect. I can imagine a would-be philosopher 

 saying, ' Tell me, you who suppose that everything 

 has its purpose, and that nothing comes by chance, 

 what is the use of these hooks ? It seems hardly 



