xxxviii LLOYD'S NATURAL HISTORY. 



" The two portions of which the proboscis is composed, seem 

 to be analogous to the maxillae or under-jaws of the mandibu 

 lated tribes,* and to receive their great development at the 

 expense of the other oral appendages, most of which are small 

 and inconspicuous. This is not the case, however, with the 

 labial palpi, which are generally of considerable size, and curved 

 upwards in such a manner as to form two projecting points in 

 front of the head. These organs are covered with hair-like 

 scales, are usually of a somewhat conical shape, and consist 

 for the most part of three articulations (see Plate I., fig. 1 2a). 

 They are attached to a triangular plate, which must be regarded 

 as the labium, or under lip, as it closes the cavity of the mouth, 

 immediately below the insertion of the trunk. On each side 

 of the latter, not far from the base, there is a minute tuber- 

 culiform projection, formed of two or three indistinct joints, 

 which together seem to represent the maxillary palpi. The 

 representation of the labrum, or upper lip, is a minute membran- 

 ous piece, usually approaching to a triangular shape, and two 

 other small projections, more or less dilated internally, and 

 placed one on each side of the proboscis at the base, are 

 analogous to the mandibles of gnawing insects. Most of 

 these parts, however, exist in a very rudimentary condition, and 

 afford another example, in addition to many already familiar 

 to us, of Nature adhering to a particular form of structure after 

 it has ceased to be subservient to any essential function, f for 

 if some of these parts are designed for the same purpose which 

 they serve so effectively when fully developed, it is not easy to 

 see how they could be employed by the insect, or in any way 

 prove serviceable to its economy." (Duncan.) 



* Bees, Beetles, &c. 



i Before the advent of Darwin, and his demonstration of the unity of 

 all living beings, rudimentary structures were a great puzzle to philosophic 

 naturalists, who found it very difficult to account for them in any rational 

 or satisfactory manner. 



