XI 



PHYLUM ARTHROPODA 



589 



The antennae vary in shape in different groups, and sometimes 

 even in the sexes of the same species. They are sometimes taper- 

 ing, sometimes moniliform, sometimes club-shaped, sometimes 

 pectinate, sometimes plume-like. In addition to functioning as 

 tactile appendages they bear the olfactory setae. The mandibles 

 are always one-jointed, and differ from those of the Crustacea in 

 never being provided 

 with a palp. An arrange- 

 ment of the mouth- 

 parts adapted for biting 

 or chewing has already 

 been described in the 

 case of the Cockroach. 

 This type is character- 

 istic of the order Or- 

 thoptera, to which the 

 Cockroach belongs, and 

 a very similar type char- 

 acterises the Coleoptera. 

 In the Hymenoptera 

 (Fig. 478) the mouth 

 parts are adapted both 

 for biting and for licking 

 and sucking ; the mandi- 

 bles (md.) and maxillae 

 (inx\) are sharp and 

 lancet-like, the middle 

 part of the labium is 

 produced into a long 

 median tongue (ligula, 

 li.) at the sides of which 

 are a pair of accessory 

 tongues or paraglossce 

 (prg.). In the Hemip- 

 ' tera there is a proboscis 

 formed from the labium 

 enclosing the stylet- 

 like mandibles and maxillae. In the Diptera (Fig. 479) the 

 mandibles (md.), usually not developed in the males, are biting or 

 piercing organs, while the basal parts of the labium form a pro- 

 boscis (mx 2 .) enclosing a spine or seta (hp.), which is a process 

 from the hypo-pharynx a chitinous process on the roof of the 

 mouth, and sometimes stylet-like maxillae (mx 1 .). In the Lepidoptera 

 (Fig. 480) the mandibles are aborted in the adult, and the maxillae 

 are developed into elongated half-tubes, which when applied 

 together form a greatly elongated tube (sr.) capable of being 

 coiled up in a spiral manner under the head, the extremity 



Li 



FIG. 478. A, mouth parts of the Honey-bee (Apis 

 mellifLca) ; B, the two pairs of maxilla? ; au, eye ; 

 a, antenna ; c. cardo ; ep. epipharynx ; Ibr. labrum ; 

 li. ligula ; m. mentum ; mm.mx 1 , first pair of maxilla? ; 

 md. mandible ; pin, palp of the first pair of maxilla? ; 

 PI'!/, paraglossa ; sm. submeiitum ; stm. stipes of the 

 first maxilla?. (From Lang.) 



