xii INSECTS OF THE SEA-SHORE 373 



Very few species attain such a size that they can be 

 seen at a distance of four or five feet ; a length of 

 four millimetres is somewhat uncommon. 



On the verge of the beach, especially where it is 

 flat and sandy, there will commonly be found a line 

 of black sea-weed, cast up by the spring-tides. In 

 the damp and fermenting mass beneath the surface 

 of the sea-weed, innumerable maggots thrive, and 

 produce throughout the year black Flies, which are 

 rather like the common House-fly, but have longer 

 wings and smaller bodies. The Flies sometimes 

 emerge in dense swarms, but more commonly settle 

 here and there on the heap of weed, especially in 

 cold weather. They occasionally fly a few miles 

 inland and visit flowers. The black pupae are buried 

 in the weed. This is the Dipterous Insect known 

 to entomologists as Coelopa frigida. The maggots 

 and pupae easily survive a short immersion in salt 

 water, to which they are occasionally, but not fre- 

 quently, subject. 



Another Dipterous fly is very common on the 

 shore. This belongs to the same large family, 

 Muscidse, as the House-fly, but to the Acalypterate 

 division, and is named Actora aestuum. It is of small 

 size and abounds in summer on the wet sand and foam 

 at the very verge of the tide. The larvae are be- 

 lieved to feed upon thrown-up seaweed (Fucus vesicu- 

 losus), and are covered at every tide. The body is 

 ten to fifteen millimetres long, cylindrical, and covered 

 with short hairs. It is a good deal like the Leather- 

 jacket (larva of the Daddy-long-legs), and like it 

 bears a number of conical fleshy processes at the 



