[ '172 J 52 ■ ' 



In those moths which have bi-pectiuate antennas, these parts are 

 almost always wider in the males. Many insects in the order of Diptera 

 are remarkable for the great size and beanty of their eyes, and these 

 organs are almost always larger in the males than in the females. 

 '^ O In describing insects it is customary, for the sake of brev- 

 O "I ity, to distinguish the sexes by signs, as shown in the margin. 



male, female. 



EXTEENAL STEUCTUEE OF INSECTS. 



The clasification of insects depends chiefly upon the structure of the 

 external and visible parts. It is necessary therefore that the student 

 should have a thorough knowledge of these parts and of the names 

 by which they are designated. But as these parts are very greatly 

 modified in the diflt'erent orders of insects, we shaU reserve a minute 

 discriptiou of them till we come to treat of them in connection 

 with the several orders respectively, and shall here give onlj^ a general 

 enumeration of them. The studeut will be much aided in understan- 

 ding the following description by comparing it with the figure of Rar- 

 palus caligiiiosus on a subsequent i)age. 



THE HEAD AND ITS APPENDAGES. 



It often becomes necessary to refer to different parts of an insect's 

 head, and they are therefore designated by particular names indicative 

 of their situation. Tliese are — 



The Hind-head, {Occiput). The Crown, {Vertex). The Fore-head, 

 (From). The Face, (J^a.c/e,s'). The Cheeks, {Genw). 



The appendages of the head are the Horns {Anteninc) ; the Eyes, 

 {Oculi) ; and the parts of the Mouth, {Trophi, or oral orf/dus.) 



The Antennce. — All insects have two more or less elongated and 

 usually many-jointed antenna", situated one on each side of the head, 

 and varying greatly, in different kinds of insects, in length and in the 

 form of their component joints. Insects have very short antennse in 

 their larva state, and in some perfect insects, such as the water-beetles, 

 {Gyrini and HydropMU), the antennpe are not longer than the head, 

 whilst in others, such as some of the longicorn beetles, they are more 

 tlian twice as long as the whole body, and in some of tlie small moths 

 of the genus Adda, they are five or six times as long. The uses of the 

 antennae are not known, but, as we have stated above, when treat- 

 ing of the senses of insects, they are supposed to be instrumental in the 

 sense of hearhig. The most common variations in the forms of the an- 

 tenn.TB are exjjressed by the following terms. Figm^es of most of these 

 forms are given on a subsequent page, in treating of the Coleoptera. 



Filiform, or thread-lila'; long and slender, and of the same, or nearly 

 the same width throughout. 



