APPENDIX II 



SHORE INSECTS 



The following short account is intended to supplement 

 the somewhat scanty references to insects in our survey 

 of the life of the sea-shore. 



Among the features which have enabled these typically 

 air-breathing creatures to extend their activities to the sea- 

 shore, we may note that they are not readily wetted, the 

 chitinous body-covering and the frequent presence of hairs 

 alike preventing this. In addition, the tough chitin delays 

 almost indefinitely the passage of the toxic salts from the 

 water to the tissues (endosmosis). The surface-film of water 

 will not pass into small openings, such as the mouth or 

 spiracles, and in any case the spiracles are guarded by hairs. 

 Furthermore, sea-shore insects are mostly small (see Miall, 

 1895). A striking point is the frequent reduction, or total 

 suppression, of wings, as seen for example in the small 

 Hemipteron Aepophilus and the beetle Aepus marinus. 

 This is generally supposed to be advantageous in preventing 

 the animals from being blown away from their narrow 

 environment. Generally speaking, however, the adaptive 

 features seen in marine insects are few as compared with 

 those which secure the survival of the fresh-water members 

 of the same group. One thinks of the many remarkable 

 arrangements for locomotion (" pond-skaters," " water- 

 boatmen "), for respiration, and for securing the survival 

 of eggs and young, which are so frequently met with in 

 fresh-water insects.'^ Probably the chief obstacle offered 

 to insect life in the sea is the constant agitation of the water. 

 The fact that shore insects so rarely swim may be almost 

 certainly attributed to this cause. We must not forget, 

 however, that Hemipterous insects belonging to the genus 



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