25 



palpi. (See tig. I, /.) The tip of the epipharynx rests between the labellae, 

 as is seen iii fig. 1, , and in fig. 2. 



The maxillae (fig. 1, -w.r) are slender, solid, chitinous rods, the outer or apical 

 halves of which lay along each side of the hypopharynx ; their basal portions pass 

 more and more outward, so that their bases are at each side of the labrum-epi- 

 pharyux. (See fig, 1, >>, *.'.) In cross-section the maxillae are reniform, with 

 the concave sides inward, gradually changing to triangular towards their tips, 

 where their outer sides are very finely and densely pubescent, (fig. 4.) Between 

 the portions represented in sections # and /, the maxillae are joined by the 

 maxillary palpi, and, at about the same time, they join a fold (/') of the labium, 

 which fold, as seen in section, surrounds the labium itself. The bases of the 

 maxillae f.r) extend deep into the head. 



The maxillary palpi (fig. 1, wp) are slender, hairy, cylindrical, and lay just 

 outside, and at the base of the proboscis. Their bases lay at the sides of the 

 labrum-epipharynx ; their tips usually directly over it. 



The labium (fig. 1, /) is slender, hairy, and its outer fifth is divided into 

 two labellae. Throughout its length, the labellae excepted, the labium forms a 

 channel (see sections y-i) for the reception of the hypopharynx and maxillae. It 

 contains two longitudinal tracheal stems, and longitudinal muscles; it is especially 

 flexible toward the tip. At its base the upper surface of the labium joins the 

 under surface of the hypopharynx, and its under surface continues, with two folds 

 (I' and I" of figs. 1, L-Y., and of- fig. 3), directly into the lower surface of the 

 head. The labellae are not jointed to the tip of the labium by a true joint, as 

 in Cide.v, but are the continuations of the two lateral halves of the labium. The 

 tip of the labium projects between them, however, as can be seen in section //, 

 where the cross-section of the tip of the labium is shown, at its first point of 

 connection with, and between the two labellae. Each labella contains a flexor 

 and extensor muscle, the flexor a little above the extensor in position. The 

 labellae are usually pressed closely together, but can be separated, as seen in 

 fig. 2, or even wider, so as to be at right angles to the axis of the proboscis. 

 On the inner side of each labella are three longitudinal grooves or channels, held 

 open by semi-rings of ehitin at right angles to their axes, and toothed on each 

 side. These, on account of their general resemblance to tracheae, were termed 

 by Suffolk' 2 pseudotracheae, in his description of them as they appear in Mnx,-a 

 vomitoria. These psendotracheae are seen in section in fig. 1, . Fig. 5, a, is 

 a perspective view of the pseudotracheae of Bombi/fiiix major, when at rest, with 

 their teeth turned inward (fig. 6, a is cross-section of the same) ; fig. 5, b, shows 



