THE INSECT WORLD. 103 



vesting should be done as soon as possible to eheck the increase 

 of the pests. 



Many species of Thrips are found on flowers, many also under 

 the bark of trees, and some forms are said to be predaceous. 

 Their life habits are not well known, but a large number winter 

 in the adult stage under such shelter as they can find, — hence, 

 cleanliness on the farm is indicated. 



For a better understanding of the characters of the more typi- 

 cal Hemiptera, we will take up the families separately ; and first 

 the Parasitica. By taking up this series before the others it is 

 not to be understood that they are higher in the scale, nor, on 

 the other hand, much lower in type ; but it is simply a matter 

 of convenience. Parasites, because of their habits, are often said 

 to be "low ;" but it is a question whether this is true, because 

 parasitism is an acquired character, and the insects are really 

 much specialized for their habit of life and well adapted to it. 

 We have in a previous chapter considered the biting lice, and 

 found that they feed more particularly upon surface structures. 

 The sucking lice, as the term indicates, obtain their food by 

 piercing the skin and sucking the animal juices or blood. The 

 mouth differs from that of the other bugs in that the proboscis 

 is fleshy and unjointed, capable of being withdrawn into the head 

 or extended, and within it are two protrusible lancets only. At 

 its base is a circlet of hooks, by means of which the insect an- 

 chors itself firmly in the skin of the infested animal. The legs 

 are " scansorial," or fitted for climbing, — that is to say, they are 

 short, heavy, set at the sides of the thorax, and the tarsus is 

 modified into a stout, slightly curved claw, opposed like a thumb 

 to the end of the tibia, which in turn is broadened at the tip and 

 a little excavated. Thus, between the end of the tibia and the 

 tarsus, the insect is able to grasp a hair so tightly that it is some- 

 times easier to pull it from the skin than to dislodge the parasite. 

 Here we have another example of insects that do not change in 

 appearance throughout their life : they simply increase in size 

 and become adult when the sexual organs are fully developed. 

 Warm-blooded animals only are infested by these sucking lice, 

 man being included under this general term. 



Three species are found on the human animal: one, Pediciilus 

 capitis, infesting the head, glues its eggs, which are known as 



