CRUSTACEA. 653 



The Humble-bee Fly. — This very curious iusect is found in the 

 early days of spring, and may be seen hovering over the primroses and 

 other spring flowers. It feeds in the same manner as the humming- 

 bird moth, and much resembles that insect in many of its habits. 



CRUSTACEA. 



Having completed our brief survey of the insects, we now proceed 

 to the Ceustacea, a very large class, in which are included the Lob- 

 sters, Crabs, Shrimps, Water-fleas, and a host of other familiar beings. 

 Even the Cirrhipeds, popularly known under the name of Barnacles, 

 are members of this large class, and a number of curious animals 

 which until lately have been classed with the spiders are now ascertained 

 to belong to the Crustacea. 



These beings can easily be separated from the insects on account of 

 their general structure, the head and throat being fused into one mass, 

 called technically the cephalothorax, the number of limbs exceeding 

 the six legs of the insects, and the mode of breathing beiug by gills, 

 and not by air-tubes. 



The name of Crustacea is sufficiently appropriate, and is given to 

 tnese creatures on account of the hard shelly crust with which their 

 bodies and limbs are covered. 



The first section of these creatures are called the Podophthalmata, 

 or Stalk-eyed Crustaceans, because their eyes are set upon footstalks. 

 The first order is that of the Ten-legged Crustaceans, so called on 

 account of the five pairs of legs that are set in each side. These are 

 exclusive of the complicated apparatus of the mouth and the jaw-feet 

 which guard its entrance. The Crabs are placed first in the list of 

 Crustaceans, and are technically called Brachyura, or Short-tailed 

 Crustaceans, because their tails are of comparatively small size and 

 are tucked under the large shielded body. In the preliminary stages, 

 however, the Crabs have tails as proportionately long as those of a 

 lobster or a cray-fish. 



As the shelly armor of the Crustaceans is, in most cases, so hard, 

 strong, and unyielding, the mode of growth might be considered a 

 problem not very easy of solution ; for with the Crustaceans the growth 

 continues during nearly the whole of life, or at all events for several 

 years after they have passed through the various changes to which they 

 are subjected in their imperfect stages of existence. Their increase 

 of size and weight is marvellously rapid, and how it can be accom- 

 plished without subjecting the Crustaceans to the lot of the starveling 

 mouse, w^ho crawled into a jar of corn, but could not crawl out again 

 after feasting on its contents, seems to partake of the character of an 

 animated puzzle. 



