30 ENTOMOLOGY FOR MEDICAL OFFICERS 



True wingless insects, with very slight metamorphosis. Two 

 orders : — Collembola and Thysnnura. 



2. Exopterygota (e^co = outside, and irTepvywroi). — Winged 

 insects (there are some wingless species in most of the 

 constituent orders, but the types of all the orders are 

 winged) ; the wings develop outside the body : meta- 

 morphosis "incomplete," though in the orders with aquatic 

 larvae the young is often very much unlike the parent. 

 Nine orders : — Orthopiera, Plecoptera, Psocida (or Corro- 

 dentid), Isoptera, Embiida, Epkemerida, Odonata, Thysanoptera, 

 Rkynchota. 



3. Endopterygota (evSov = inside, and TrrepvyooTog). — Winged 

 insects (there are some wingless species in most of the orders, 

 but the types of all the orders are winged) ; the wings start 

 their development as invaginations inside the body : meta- 

 morphosis " complete." Eight orders : — Neuroptera, Mecap- 

 tei-a, Trichoptera, Lepidoptera, Coleoptera, Strepsiptera, Diptera, 

 Hymenoptera. 



4. Anapterygota {ava in the sense of retrogression, and 

 TTTepuycoTo'?). — Wingless parasitic insects of mammals and 

 birds ; probably descended from winged ancestors. A mixed 

 group : it includes the Siphonapter'a, which are probably 

 related to the Diptera or possibly to the Coleoptera ; the 

 Mallophaga, which are probably related to the Orthoptera; 

 and the Anoplura, which may be related to the Rhynchota. 



From our practical point of view, it is permissible to 

 disregard natural affinities and to treat insects in some such 

 order as follows : — • 



(«) Orders which include species that "bite" or sting 

 man, or in some direct way threaten his health : — 



1. Diptera (Flies) 3. Anoplura (Lice) 



2. Siphonaptera (Fleas) 4. Rhynchota (Bugs) 



5. Hymenoptera (Wasps, Bees) 



{]}) Orders which include species, outside the orders 

 already specified, that damage food, habitations, etc. : — 



6. Coleoptera {^^eC^^s) 9. /s-o//«'«(" White Ants ") 



7. Lepidoptera (Moths) 10. Corrodentia (Book-lice) 



8. Orthoptera (Cock- 11. TJiysanura (Fish- 



roaches, etc.) insects) 



