INTRODUCTION 



The front part of the head is called the face, the upper part 

 the crown ; sometimes there is a distinct raised transverse fillet 

 between the antennae; the sides are mainly occupied by the large 

 eyes, and the lower part by the mouth-organs ; the back, forming 

 the junction with the thorax, is covered by a collar of scales. 

 The organs attached to the head are all paired ; these are the 

 eyes, ocelli, antennae, maxillae (combined to form the proboscis), 

 mandibles, maxillary palpi, and labial palpi. Occasionally the 

 chitinous substance of the head is enlarged to form a pro- 

 tuberance, which is of the nature of an excrescence and not a 

 true organ. 



The eyes are compound, being made up of a very large 

 number of simple lenses, the whole having a more or less hemi- 

 spherical surface, which is sometimes furnished with erect hairs, 

 but usually glabrous. 



The ocelli are small simple lenses, placed on the crown close 

 behind the eyes ; they are rarely conspicuous, often partially 

 or quite hidden in scales, or entirely absent ; their function is 

 not understood, but as they are so frequently obsolete, they 

 can hardly be of much importance. They are often erroneously 

 stated to be absent when only concealed ; and in general not 

 much stress should be laid on them for purposes of classifi- 

 cation. 



The antennae are sense-organs, composed of an indefinite 

 number of joints, inserted above the eyes ; they vary much in 

 length and structure. Often they are pectinated; i.e. the upper 

 angle of each joint is developed into a slender chitinous process 

 like the tooth of a comb ; if there are two rows of such pro- 

 cesses, the antenna is bipectinated, if one, unipectinated. If not 

 pectinated, they may be dentate, serrate, or filiform. Very 

 frequently they are ciliated; i.e. furnished with one or two 

 series of usually short fine hairs, closely and evenly arranged ; 

 when the hairs are collected into fascicles or bundles, which 

 usually happens when they are longer, the antennae are said 

 to be fasciculate-ciliated. Occasionally they are pubescent ; i.e. 

 clothed all over their surface with a short fine down. Some- 

 times they are furnished with special structures, such as thicken- 

 ings, notches, sinuations, or tufts of scales. The nature of the 

 sense located in the antennae is not known ; but very generally 

 the antennae of the male show an increase of development as 

 compared with those of the female, and there can be little 

 doubt that one of their functions is to enable the former to find 

 the latter. 



