216 THE FOOD OF ANIMALS 



legless grubs which live underground and possess biting mouth- 

 parts, with which, according to some observers, they attack the 

 roots of grasses and other plants. 



The wasp-like HOVER- FLIES (species of Syrpkus) frequent 

 flowers, upon the pollen and nectar of which they feed. Although 

 the piercing mouth-parts are retained they are not known to be 

 of use, though this is one of the innumerable cases where there 

 is a lack of detailed and accurate observation. We have here 

 a good instance of marked difference in feeding habits between 

 larva and adult, for the former is a legless maggot which re- 

 lentlessly pursues plant-lice (aphides), the juicy bodies of which 

 it sucks as a school-boy does an orange. Closely related to these 

 forms are the Drone -Flies (species of Eristalis), which closely 

 resemble bees, and visit flowers for the same reasons as their 

 congeners. The curious aquatic larva is known as the Rat- 

 tailed Maggot (from the long breathing- tube which projects from 

 its posterior end), and feeds upon decaying vegetable matter or 

 upon the refuse matter which saturates the filthy ponds, &c., in 

 which it is often to be found. 



Further mention will be made of Diptera which feed on vege- 

 table matter when agricultural pests are dealt with. 



FRINGE-WINGED INSECTS (THYSANOPTERA) 



The best -known member of this order is the minute Corn- 

 Thrips (Thrips cerealiwn) (see vol. i, p. 355), often found in large 

 numbers in the flowers of grain crops. It possesses four narrow 

 fringed wings, and the most remarkable parts related to its mouth 

 are three piercing stylets, of which two are probably parts of the 

 first maxillce, and the third one derived from the mandibles. It 

 is usually stated that they feed upon pollen, and are also able to 

 pierce the flowers in which they live for the purpose of obtaining 

 sap. They are reckoned among the innumerable pests of agri- 

 culture. 



BUGS (HEMIPTERA) 



The Bugs, using the word in a very broad sense, which con- 

 stitute this large order, possess piercing and sucking mouth-parts, 

 which have already been briefly described (p. 122). The young 

 forms resemble, the adults in most particulars of form and struc- 

 ture, including the nature of the mouth-parts, there never being 

 therefore the sharp contrast between a biting larva and a sucking 



