HOW TO USE THE KEYS 



Keys are used for the ready identification of insects and 

 other living things. They are based on an orderly elimination of 

 the characters that do not fit the case in hand. I'ost insect 

 keys are dichotomous, i.e., they consider only two possibilities 

 at one time. To use the keys in this book, take the insect to be 

 Identified and turn to the "Key to the Orders of Insects" 

 p. 37. Compare the insect with la and lb of the key. Supposing 

 it has "no wings" we then turn to #17 p. 45 and compare 17a with 

 17b. If our sDecimen has a "narrov/ waist" we would suspect it to 

 belong to Order XXV, Hymenoptera and we vjould then turn to p. 106 

 to the "Key to the Llore Coiiiirion Families of the F.ymienoptera," and 

 again starting with la and lb would find it to belong to lb which 

 would refer us to #5. Now if we can find no "erect scale on the 

 petiole" we are referred to #6. Supposing our specimen is "cov- 

 ered on thorax or abdomen with red hairs, xie would believe it to 

 be a fem.ale Velvet Ant belonging to Family 50, I/'utillidae . If 

 our specim.en closely resemibled Fig. 230 we could feel quite sure 

 of our Identification. If it seemed to agree wholly with the 

 picture and the description it would be believed to be the 

 species Dasymutilla interrupta Banl^.s. 



Of course, almost every family has numerous species of Insects 

 belonging to it, so one should not be too hasty in deciding that 

 his specimen is the one described and pictured here to illustrate 

 the fajnily. 



It should be borne in m.lnd that keys are neither infallible 

 nor final. The ones given here are designed to aid in deter- 

 mining the family to which an insect belongs. To make these keys 

 more usable miany of the less common families have been om.itted. 

 If one should attem.pt to name a specimen belonging to one of 

 these omitted families, he v^ould surely end at the wrong place, 

 if he could get anywhere at all with it. 



The beginner needs to know som.ething about the external 

 structure of insects to use the keys intelligently. 



All of the hundreds of thousands of different kinds of in- 

 sects are alike In having bodies of three parts; head, thorax, 

 and abdomen, and in having three pairs of legs. The head bears 

 two compound eyes and often two, or more frequently three simple 

 eyes (ocelli). A pair of antennae or feelers are always found on 



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