THE INSECT WORLD. 



lOI 



the species live and feed upon animals, this is called Parasitica. 

 All these agree, however, in the essential character of the order, 

 which is found in the structure of the mouth parts. Throughout 

 all series we find the head prolonged into a jointed beak or ros- 

 trum, obsolete only in the Parasitica, and within, protected by- 

 it, is a series of three or four slender, needle-Hke lancets. The 

 beak is open in front, and the lancets may be protruded at the 

 tip. In most species, when the insect is feeding, the lancets are 

 so deeply inserted that the beak bends at or about the middle, 

 leaving them entirely free except at the tip. In other cases, 

 among predaceous types, the beak is too rigid to bend thus, and 

 it, as well as the lancets, is forced into the tissues upon which 

 the insect feeds. It is to insects of this order only that the ento- 

 mologist applies the term biLg'^ and when he uses that word 

 he always refers to one of the Hemiptera. It has been indicated 

 that the creatures gain their food by piercing and sucking, and 

 this is a radically different method from anything found hereto- 

 fore. We have now insects that are incapable of chewing food, 

 and subsist only upon liquids which must be drawn from living 

 tissue, be it animal or vegetable. A large proportion of the spe- 

 cies is injurious ; but there are also groups of predaceous habit, 

 feeding upon other insects in whole or in part, that may be con- 

 sidered beneficial. In their development the insects belong to 

 that series in which the metamorphosis is incomplete ; but there 

 is an exception in the males of certain bark-lice, where there is a 

 real, quiescent pupal stage 



Before going further on this subject it is necessary to refer to 

 the peculiar little species known as Thrips, and belonging to the 

 family ThripidcB. They are now as a rule, and properly, sepa- 

 rated from the true He77iiptera under the ordinal terms Thysan- 

 optera, meaning fringe-winged, or Physopoda, meaning bladder- 

 footed. They are always small in size, slender, active, with the 

 head so narrow that they seem pointed at both ends. The wings 

 are laid longitudinally on the back, and are very narrow, trans- 

 parent, without veins or with mere rudiments, but with lengthy 

 fringes, which give them a characteristic and peculiar appearance. 

 The feet are not terminated by pointed claws as usual, but by 

 small, bladder-like dilations of the terminal joints. They run 

 and fly readily, and some of them jump much as do spring-tails. 



