Economic Importance of Animals 563 



Order 15 — Neuroptera: The larva (hellgrammite) of the Dobson fly 

 is used as fish bait (Fig. 294). The larva of the lacewing fly (Aphis 

 lion) destroys plant lice (Aphids) by sucking blood. The larvae of ant 

 lions ("doodlebugs") wait at the bottom of a pit made in sand, dirt, or 

 decayed wood, where they capture and destroy many types of insects. 



Order 16 — Coleoptera: The dried bodies of a certain European blis- 

 ter beetle known as "Spanish fly" are used as a source of cantharidin, 

 which is used for medicinal purposes. The larvae of click beetles, com- 

 monly known as "wire worms," cause extensive damage in plants. The 

 metallic wood-boring beetles injure shade, forest, and fruit trees by bor- 

 ing in them. Some of the so-called checkered beetles destroy some of 

 the larvae of wood-boring insects. The so-called death-watch beetles 

 damage wood greatly by boring in it. The light-producing secretion 

 (luciferin) of fireflies (beetles) is used for illumination and is a source 

 for study in the attempt to duplicate this material in the laboratory. 



Fig. 295. — Tiger beetle of the order Coleoptera. Note the light markings on the 



wings. 



This material gives off light with a minimum of heat. The tiger beetles 

 (Fig. 295), both in the adult and larval stages, destroy large numbers 

 of other harmful insects. Most of the ground beetles (Fig. 296) are 

 predacious and attack such insects as leaf-eating insects, canker worms, 

 cutworms, and the so-called tent caterpillars. The carnivorous water 

 beetles attack numerous aquatic insects, including the mosquito. The 

 ladybird beetles or "lady bugs" (Fig. 297) are predacious in both adult 

 and larval stages, when they attack detrimental scale insects and plant 

 Aphids in particular. They are consequently of great importance and 

 the various species should be protected so that they may continue their 

 useful habit. The Mexican bean beetle is rapidly becoming a serious 

 pest of garden products. When bean plants are all destroyed, they do 

 not hesitate to attack other plants. A certain species of powder-post 



