6 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



Insects in general. — The term iusect is applied to that class of jointed 

 animals {Arthropoda) whose bodies are divided into three regions or 

 sections, called the head, thorax, and hind-body or abdomen. They 

 usually have three pairs of legs attached to the mid-body or thorax, 

 and two pairs of wings. Most insects pass through a series of changes. 

 In the butterfly, for example, after hatching from the egg as a cater- 

 pillar {larva), it transforms to a chrysalis (^i(2>a),^linally changing to the 

 imago or winged insect. The insects form a class comprising about 

 200,000 known species. 



They are divided into sixteen orders (not including those which are 

 extinct), as may be seen by the following tabular view copied from the 

 author's " Zoology," which briefly represents the more apparent, super- 

 ficial differences between the groups. The list begins with the lowest, 

 ending with the highest. 



Orders of insects now living, 



1. Wingless, often with a spring. Thysanura: Spring-tails, etc. 



2. Fore wings minute, elytra-like Dermaptera : Earwig. 



3. Wings net-veined; fore wings narrow; hind 



wings folded Orthoptera : Locusts, Grassnoppera. 



4. Fournet-veined wings; mouth -parts adapted 



for biting Platyptera : White Ants, Bird-lice. 



5. Wings net- veined, equal Odonata: Dragon-flies. 



6. Wings net- veined, unequal Plectoptera : May flies. 



7. Mouth-parts beak-like, but with palpi Thysanoptera : Thrips. 



8. Mouth-parts forming a beak for sucking; no 



palpi Hemiptera : Bugs. 



9. Wings net-veined; metamorphosis complete -iV^ei/ro/Jfera ; Lace-winged Fly, etc. 



10. Wings long and narrow ; body with a forceps. Jl/eca/>'ej'a; Panorpa. 



11. Wings not not-veined Trichoptera : Caddis-fly. 



12. Fore wings sheathing the hinder ones Co leoptei-a : Beetles. 



13. Wingless, parasitic Siphonaptera : Fleas. 



14. One pair of wings Diptera : Flies. 



15. Four wings and body scaled Lepidoptera: Butterflies. 



IG. Fourclear wings; hinder pair small; a tongue. £r]/»ienoj)(era : Bees, Wasps, etc. 



Allied to the insects are the myriopods, or centipedes and galley- 

 worms, none of which are injurious to forest or shade-trees, although 

 the smaller kinds of centipedes {Lithobius, etc.), occur under the bark of 

 decayed trees. No spiders or allied forms, comprising the class Arach- 

 nida, are injurious to vegetation, except certain mites (Acarina) whose 

 forms and gall making habits are peculiar. Many spiders take up 

 their abode in the leaves of shade and forest trees, but none are known 

 to be injurious. The false-scorpions (Chelifer, etc.) often occur under 

 the bark of decayed trees, but they are more useful than otherwise, as 

 they probably devour the smaller wood-boring larvae. 



The bulk of our destructive forest insects belong to the orders com- 

 prising the beetles, the caterpillars, gall-flies, saw-fly larvae, and tbe 

 bugs. We will mention them in the order of their importance as 

 destructive to shade and forest trees. 



