The perfect swarm / 
Rob Waring, series editor. 
 - Boston :  Heinle/Cengage Learning,  c2010 
 - 48 p. :  col. ill., col. map ;  21 cm +  1 video disc (sd., col. ; 4 3/4 in.) 
 - Footprint reading library. Incredible animals .
 - Footprint reading library.   Incredible animals. .
<br/><br/> "The footprints reading library introduces sights and sounds from around the world with original video material developed by National Geographic Digital Media. These readers offer real-life stories in print, audio and video to develop English language skills" -- inside cover. 
<br/><br/> In the 1800's, the Rock Mountain locust brought massive destruction to Western settlers. Then, the insects suddenly disappeared almost without a trace. Now scientists hope to find a reason for the locust's extinction. What caused the Rocky Mountain locust to disappear? Where will the scientists find the answers? 
<br/><br/><label>ISBN: </label>9781424012275 1424012279 9781424026975 (DVD) 1424026970 (DVD) 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Readers.<br/>Rocky Mountain locust.<br/>Insects --Juvenile literature.