300 THE SEA SHORE 



of the tide during the whole of the summer months. But although 

 these insects are so very numerous, we do not find among them 

 a particularly large number of species, their abundance being due 

 more to the extreme prolificacy of those that occur. 



In this order, which includes all gnat-like creatures, as well as 

 those insects that are generally known as flies, the first pair of 

 wings are well developed, while the second pair are rudimentary, 

 and represented merely by a pair of scales, or by two little pin-like 

 bodies called the balancers or halteres. Some are provided with 

 piercing organs by means of which they can inflict a small wound 

 and then extract the juices of their victim, as does the female gnat, 

 but the majority have a proboscis adapted for suction only. The 

 larvae of the Diptera are generally limbless maggots, gifted with a 

 pair of jaws, and they are usually very voracious feeders, devouring 

 decomposing animal or vegetable matter in enormous quantities. 



If we turn over a fermenting mass of the miscellaneous matter 

 thrown up on the beach quite beyond the reach of the tides, we 

 may observe a multitude of little maggots which feed on the moist, 

 odorous portion that was protected from the direct rays of the sun, 

 together with a number of dark-coloured pupae that lie at the 

 very bottom of the heap or buried in the sand below. These are 

 two stages of the black fly (Coelopa frigida) that is so attentive to 

 us when we rest on the dry sand above high -water mark. This fly 

 is very like the common house-fly in general appearance, though 

 its body is rather smaller. Other species of the same genus often 

 accompany them, all being very similar in general appearance and 

 habits, and none of the larvae seem adapted to a life in the water. 

 They are always found beyond the reach of the tide, and are 

 drowned if submerged for any length of time. 



Another species belonging to the genus Actora will often be 

 seen in the same company, and this is readily distinguished by 

 their lighter greyish colour and its superior size. Also, along 

 the water-line, we often meet with species of the family Dolicho- 

 podidce, so called on account of the length of their legs, and noted 

 for the beautiful metallic colours which adorn their bodies. These 

 flies are carnivorous in habit, deriving their food from living as well 

 as from freshly killed animals, and their short, fleshy proboscis 

 contains a piercing bristle by which they can puncture the skins of 

 the animals that provide them with food. Most of the flies of this 

 group live on trees, walls, fences, &c., where they pursue and attack 

 their prey, but certain species follow the line of breakers on the 



