MARINE ARTHROPODS 301 



sea shore, as before indicated, and obtain their food from the various 

 marine animals that are stranded on the beach. A peculiar feature 

 of the family is the nature of the abdomen of the males, which is 

 bent under the body and furnished with a number of appendages. 



Another marine dipterous insect is a gnat-like fly closely allied 

 to Chironomus, which we have described in a former work * of this 

 series dealing with fresh-water life ; and it will be sufficient to 

 mention here that Chironomus is commonly known as the window- 

 gnat on account of the frequency with which it may be seen flying 

 on the windows of our dwellings ; also that the larva, known 

 popularly as the bloodworm, is truly aquatic in habit, being able to 

 swim by rapidly looping its body in opposite directions, and being 

 provided with a breathing apparatus adapted for the absorption of 

 the oxygen gas contained in solution in water. The larva of the 

 marine species referred to above may sometimes be seen in rock 

 pools, where it shelters itself among the sediment at the bottom. 

 It is much like the bloodworm in appearance and structure, but its 

 body is greenish instead of red. 



The last order of insects calling for notice here is the Coleoptera 

 or sheath-winged insects, popularly known as beetles, and cha- 

 racterised by the hard and horny nature of the front pair of wings 

 (elytra), which are modified into sheaths and serve to protect the 

 second pair ; the latter are thin and membranous, usually adapted 

 for flight, and lie folded beneath the former when not in use. 



One large section of beetles is known as the Oeodephaga or 

 Ground Beetles a group of very predaceous insects that burrow 

 into the soil and attack almost every living thing that comes in 

 their way, and well represented by numerous species that may be 

 found in our gardens, and, in fact, almost everywhere. 



A considerable number of these insects show a decided pre- 

 ference for salt marshes and the sea shore, where they hide under 

 stones, or burrow into the sand or mud in search of their prey. 

 They are not marine in the strictest sense of the word, for they are 

 not adapted for a life of submersion in water, either in the larval 

 or in the perfect condition ; yet they are often found below high- 

 water level, and some species burrow into the sand of the beach as 

 the tide advances, allowing the water to cover them for hours 

 together. 



One interesting family of the ground beetles (the Bembidiidce) 

 includes several small species, all of which frequent salt and wet 

 * Life in Ponds and Streams. 



