212 



HIGH SCHOOL ZOOLOGY. 



winged insects (Neuroptera), and, to distinguish them from 

 these, the forms referred to are called Pseudo-neuroplera. 

 Belonging here are the dragon-flies (LibeUulidoi), May-flies 

 {Ejihemeridce), stone-flies {Perlidce), all of which have aquatic 

 Iarvs3 (into the tracheae of which air is absoibed through 

 jieculiar expansions of the body-wall known as tracheal gills), 

 but there are also forms with terrestrial larvae, such, as the 

 Fsocidce (very small insects which live like plant-lice chiefly on 

 hardwood trees, and often attract attention by the woolly -looking 

 masses which they form). 



Allied to these are the troinccal Termites, often called "white ants," 

 because they live a social life iu colonies and build nests. An African 

 species — Termes helUcosus — builds towers 12 or 15 feet high ; in addition 

 to the males and females, the inhabitants are partly wingless neuters, 

 most of which undertake the work, but some the defence of the colony, 

 and are tlierefore called workers and soldiers. 



Occupying an intermediate place between the Orthoptera and the next 

 order, is the family Tlirypskke, including minute insects which have the 

 parts of the mouth adapted for sucking vegetable juices. They often 

 attack cultivated plants in great numbers, causing destruction, e.g., of 

 the hay and onion crops. The -wings of the adults are margined by long 

 delicate hairs. 



30. Like the Orthoptera, the Hemiptera are insects with an in- 

 complete metamorphosis, but the parts of the mouth are gener- 

 ally modified for sucking, the labium being converted into a 

 grooved and jointed proboscis (generally folded back underneath 

 the thorax), in which the mandibles and the maxillae lie in the 

 form of slender stylets (Fig. 146, 2). 



Fig-. 146, 1, ?. S — Diagram of transections of the proboscis of dipterous, lieniip- 

 terous, andlepidopteious insects. (After Dimmock, Graber, and Miihr, respectively). 



7c, labriim and ejiipharynx; Ih, labrnm, la, labium, (between the two are the 

 mandibles and maxilla;, and in 1, the IniJOpharynx); inx, maxilUe. 



