Fig. 85.—Head of honey bee, worker: a, antenna; g, epipharynx; m, mandible; mx, maxilla; mxp, maxillary palpus; pg, paraglossa; lp, labial palpus; l, hypopharynx; b, its spoon.—After Cheshire; from Bull. Div. Ent. U. S. Dept. Agr.
“These central and side ducts run down to that part of the tongue where the spoon, or bouton (K, Fig. 86) is placed. This is provided with very delicate split hairs (b, Fig. 86) capable of brushing up the most minute quantity of nectar, which by capillarity is at once transferred by the gathering hairs (which are here numerous, long, and thin) to two side groove-like forms at the back of the bouton, and which are really the opened-out extremity of the centre and side ducts, assuming, immediately above the bouton, the form seen in F, Fig. 86. The central duct, which is only from 1
600 inch to 1
1000 inch in diameter, because of its smaller size, and so greater capillary attraction, receives the nectar, if insufficient in quantity to fill the side ducts. But good honey-yielding plants would bring both centre and side ducts into requisition. The nectar is sucked up until it reaches the paraglossæ (pa, B, Fig. 86), which are plate-like in front, but membranous extensions, like small aprons, behind; and by these the nectar reaches the front of the tongue, to be swallowed as before described.”
Fig. 86.—Tongue or ligula of the honey bee: A, under side of the tongue; lp, labial palpi; r, r, rod; p, pouch; sh, sheath; gh, gathering hairs; b, bouton or spoon. B, under lip or labium, with appendages, partly dissected; l, lora or submentum; a, a, retractor linguæ longus; sd, salivary duct; rb and b, retractor linguæ biceps; mx, maxillæ; lp, labial palpi; pa, paraglossa; gr, feeding groove; sh, sheath of ligula. C, D, E, sections of ligula; hp, hyaline plate of maxilla; h, hairs acting as stops; mx, maxilla; lp, labial palpi; sd, side duct. F, cross-section of extremity of tongue near the “spoon”; th, tactile hairs; r, rod; n, nucleus; gh, gathering hairs. G, cross-section of tongue without gathering hairs, × 400 times; sh, sheath; b, blood space; t, trachea: ng, gustatory nerve; cd, central duct; sd, lateral duct; pm, plaited membrane. H, same as G, but magnified two hundred times, and with pm, plaited membrane, turned outwards; h, closing hairs; lp, labial palpi; b, blood; n, nucleus; r, rod; h, closing hairs. I, small portion of the sheath; lettering as before. K, extremity of the tongue, with spoon; b, branching hairs for gathering.—After Cheshire.
Cheshire then settles the question which has been in dispute since the time of Swammerdam, whether the bee’s tongue is solid or tubular. He agrees with Wolff that the duct is a trough and not a tube, and proves it by a satisfactory experiment. He remarks:
Fig. 87.—Longitudinal section through the head of the honey bee, ♀, just outside of right antenna: ant, antenna with three muscles attached to mes, mesocephalic pillar; cl, clypeus; lbr, labrum; 1, chyle-gland (system no. 1, of Siebold); o, opening of the same; oc, ocellus; br, brain; n, neck; th, thorax; oe, œsophagus; s.d2, s.d3, common salivary ducts of systems 2 and 3; v, salivary valve; c, cardo; ph, pharynx; mx′, labium; mx.′p, labial palpi; mt, mentum; mx, maxilla; hyp, hypopharynx; s, bouton.—After Cheshire.
“Bees have the power, by driving blood into the tongue, of forcing the rod out from the sheath, and distending the wrinkled membrane so that in section it appears as at H, Fig. 86, the membrane assuming the form of a pouch, given in full length at A. It will be seen at once that this disposition of parts abolishes the side ducts, but brings the central duct to the external surface. The object of this curious capability on the part of the bee is, in my opinion, to permit of cleaning away any pollen grains, or other impediment that may collect in the side ducts. The membrane is greasy in nature, and substances or fluids can be removed from it as easily as water from polished metal. If, now, the sides of a needle, previously dipped into clove oil in which rosanilin (magenta) has been dissolved, so as to stain it strongly red, be touched on the centre of the rod, the oil immediately enters, and passes rapidly upwards and downwards, filling the trough.”
Does the hypopharynx represent a distinct segment?—The facts which suggest that the hypopharynx may possibly represent a highly modified pair of appendages, arising from a distinct intermaxillary segment, are these: Heymons plainly shows that, in the embryo of Lepisma, the hypopharynx originates as a transverse segment-like fold in front of the 2d maxillary segment, and larger than it, and though he does not mention it in his text, it appears like the rudiment of a distinct segment; the hypopharynx of Ephemeridæ; arises and remains separate in the nymph from the labium (see Heymons’ Fig. 29, and there are two lateral projections; see also Fig. 72, and Vayssiere’s view that it may represent a pair of appendages; Kolbe also regards it as representing a third pair of maxillæ, his endolabium, p. 213). Though what is called an unpaired organ, it is composed of, or supported by, two bilaterally symmetrical styles, both in Myriopods (Fig. 6, labiella, stil) and in insects (Fig. 77, etc.). On the other hand, in the embryo of pterygote insects, an intermaxillary segment has not been yet detected.