THE MOUTH-PARTS OF PANGONIA LONGIROSTRIS. 



261 



apex is effected by a strong chitinisation of the central portion forming a straight 

 rod. This structure tapers slightly distally, and divides at the base into two rods, 

 each of which passes to the edge of the labrum-epipharynx. The sides of the whole 

 organ are hairy, starting from a point which is half-way down the chitinous rod and 

 continuing towards the base, the hairs decreasing in size. Ventrally a channel is 

 formed by the downward extension of the edges of this organ. 



(4). Hypopharynx (PI. vi, fig. 4). — A slender tapering rod, but swelling out near 

 the apex, which is broad and notched in the centre. The salivary duct runs along 

 the whole length and opens near the extremity (text-fig. 6). 



Fig. 6. Apex of hypopharynx of $ from 

 ventral aspect ; greatly enlarged. 



(5). Labium. — The most noticeable feature of this species is the labium, which 

 forms the long proboscis giving the insect its specific name. The organ lies ventral 

 to all the other trophi and is loosely attached to the head, its base being enclosed 

 in a basal membrane, the conjunctive membrane of Meinert (10). The labium extends 

 directly forwards in front of the head, and is grooved on its dorsal surface, the other 

 mouth-parts lying within this groove. It is a rather broad organ, and stiff, its 

 surface being strengthened at intervals by transverse bands of brown chitin. At 

 its distal end are the two labella, each of which is so situated that it forms a right 

 or left half of the apex of the labium. The two labella are flattened from side to 



Fig. 7. One of the spine-like processes of 

 labellum of $ ( x 830). 



side, and not horizontally as in the rest of the proboscis. They are united at their 

 bases, but are separate distally ; they are convex externally and concave internally, 

 and each contains within it a number of pseudotracheae. 



The external surface of each labellum (PI. vi, fig. 1) has a honeycombed appearance, 

 and bears some short, fairly strong spines projecting outwards from it (text- fig. 7). 

 As stated above, Dr. Imms has found this species only on flowers belonging either 

 to the order Scrophulariaceae or to the Labiatae, in both of which the flowers are 

 tubular. In view of this observation, I would suggest that the use of these spines 

 is to steady the insect somewhat when feeding on nectar. Having inserted its 



