212 



INSECTS OF SAMOA. 



the labrum and labium have their surfaces very strongly reticulate ; on the 

 abdominal segments the central areas are more definitely shagreened, and this 

 condition is much more conspicuous between the eighth and ninth segments 

 (Text-fig. 186). The shagreened surfaces no doubt facilitate the movements of 

 the larva in its burrow. There are nine pairs of spiracles, of which one pair is on 

 the mesothorax, each spiracle being situate anteriorly on one side and opening 

 somewhat ventrally. The other eight pairs are on the first eight abdominal 

 segments, each spiracle similarly occupying a lateral position but opening some- 

 what dorsally. In the present preparation all the spiracles can easily be traced 

 by means of the portions of tracheae attached to them. The larva is devoid of 

 legs, and I cannot trace any indication of rough or papilliferous surfaces at 

 points where they should normally be found, unless the clusters of dots indicated 

 by X in Text-fig. 17 are to be considered as such. 



Although the present specimen appears to be nearly full-fed, this is 

 probably not the case ; nevertheless the structural details are doubtless the 

 same as in a full-fed larva. 



Anatomy of the larval head (Text-figs. 17, 18a, b, c). 



The head (Text-fig. 18a) is of the type usually found in larvae which are 

 borers or leaf -miners. It is formed by a large chitinised plate, which is deeply 

 divided into two elongate lobes and has the shape shown in Text-fig. 17 (I). There 

 are strongly chitinised ridges acting as supports along the middle, and the 

 whole head is imbedded in the prothorax except its anterior edge, each side of 

 which is rounded, bearing an antenna, the middle portion being occupied by the 

 mouth-parts. The buccal cavity is formed by labrum or upper membranous 

 structure, the two mandibles and the labium or lower lip. The labrum is 

 reinforced by a chitinous support along the middle ; at its anterior edge and on 

 the sides there are numerous papilliform bristles forming a brush-like structure. 

 The mandible is triangular, its inner side being produced into a convex sharp 

 edge without any teeth. The labium is membranous, deeply cleft in the middle 

 and thus divided into two rounded lobes. Along the edge of each lobe there are 

 numerous papilliform bristles. On each side of the labium a rather long and 

 pointed palpus is visible. Situated on the upper edge of the exposed portion 

 of the head and externally to the mandibles are the antennae. Each antenna 

 is composed of three segments, a basal, a median and an apical ; the basal seg- 



