ARTHROPODA. 301 



labial palpi are inserted in the notches. They are described by the 

 authority quoted as three-jointed, with a moveable base. It is difficult 

 to homologise with certainty the parts of so modified an organ. It is 

 possible that this mentum may represent more than the part so termed in 

 Periplaneta. 



Cicindelidae. See Westwood, Introduction to Modem Classification of Insects, 

 vol. i. p. 47, 1839. 



FIG. 5. The mouth-parts of the Honey-bee, Apis mellifica, worker. Drawn from a specimen 

 as seen from the aboral surface and removed from the head. 



a-d'. Parts of the labium, 



a. The lingua or tongue : a long, narrow organ covered with setae, which 



are arranged in transverse rows, and increase in length from the 

 base to the apex of the tongue. In every fifth row there are touch 

 (?) papillae mingled with the setae. The tongue ends with a concave 

 disc, the aboral surface of which carries branched hairs. The whole 

 aboral surface of the organ is traversed by a longitudinal groove. 

 The sides of the groove are thin, but its floor is thickened, forming 

 a grooved rod, which extends as far as the terminal disc. The 

 groove and rod appear to be of functional importance in the act of 

 gathering honey. 



b. The four-jointed labial palp. The basal joint is long and grooved 



internally. The groove assists with the lingua to make a channel 

 along which the honey flows. Between the bases of the palpi and 

 lingua lie the paraglossae. 



c. Mentum. The duct of the salivary gland opens on its inner surface 



at the root of the tongue and beneath a small valve. 



d. Submentum. 



d'. Lora of Kirby and Spence (Introduction to Entomology, vol. iii. 1826, 

 p. 367), commonly found in Hymenoptera. It supports the sub- 

 mentum centrally, and at each extremity it is connected to the 

 cardo of the maxilla. It pushes forwards the sub-mentum, mentum, 

 &c., when the mouth-parts are protruded for the purpose of suction. 



e-g. Parts of maxilla. 



e. The lacinia, / the palp. 



f. The stipes and 



g. The cardo of the maxilla. 



The palp is generally stated to be one-jointed. It appears to be 

 really imperfectly two-jointed. In some Apidae it has as many as six 

 joints. 



h. The Mandible. Its inner surface is concave, and bears two oblique 

 ridges on which hairs are implanted. 



