550 Animal Biology 



Economic Importance of Representatives of the Orders of Insects. — 



Order 1 — Thysanura: The common silverfish, or bristletail, Uves on 

 starchy materials and such things as book bindings, wall paper paste, 

 and starched clothing. They are particularly common in dark, moist 

 places (Fig. 273). 



Order 2 — Collembola: The springtails (Figs. 204 and 274) are com- 

 mon under stones and decaying leaves and w^ood, etc., where they live 

 on decaying materials. Sometimes certain kinds known as snow "fleas" 

 (Fig. 203) are abundant on the surface of snow, where they appear as 

 tiny black specks which spring away because of a special springlike struc- 

 ture on the ventral side of the abdomen. They may be a pest in maple 

 sugar camps by collecting in large numbers in the collected sap. 



A. 



B. 



Fig. 272. — Lead-cable borer {Scohicia declivis) of the order Coleoptera, show- 

 ing an adult, A, and larva, B. (From Burke, Hartman, and Snyder: The Lead- 

 Cable Borer or "Short-Circut Beetle" in California, U. S. Department of Agricul- 

 ture; courtesy of Department of Entomology and Plant Quarantine.) 



Order 3 — Ephemerida: The larvae and adult May flies (lake flies) 

 (Fig. 275) are a source of food for fish. The larvae develop in water 

 for one to three years, depending on the species. Especially during their 

 emergence periods in the summer, their collection in large numbers and 

 their decomposition around lights and on bathing beaches are great 

 sources of annoyance. The adults cannot harm man because of the 

 absence of stings and well-developed mouth parts. 



Order 4 — Odonata: The dragonflies ("darning needles") (Figs. 205 

 and 276) as adults and larvae are enemies of mosquitoes during the day, 



