As Newport remarks, the office of the maxillæ in the mandibulate insects is of a twofold kind; since they are adapted not only for seizing and retaining the food in the mouth, but also as accessory jaws, since they aid the mandibles in comminuting it before it is passed on to the pharynx and swallowed. Hence, as the food varies so much in nature and situation, it will be readily seen that the maxillæ, especially their distal parts, vary correspondingly. Thus far no close observations on the exact use of the first and second maxillæ have been published. The palpi also are not only organs of touch, but in some cases act as hands and also bear minute sense-organs, the function of which is unknown, but would appear to be usually that of smell. [Illustration: FIG. 63.—_Selandria_ larva, common on _Carya porcina_, with details of mouth-parts: _leg_, leg; _mx_, maxilla; _gal_, galea; _lac_, lacinia. ] =The second maxillæ.=—The “under-lip” or labium of insects is formed by the fusion at the basal portion of what in the embryo are separate appendages, and which arise in the same manner as the first maxillæ. They are invariably solidly united, no cases of partial or incomplete fusion being known. The so-called labium is situated in front of the gula or gular region, and is bounded on each side by the gena, or cheek. As already observed, the second maxillæ appear to be the appendages of the last or occipital segment of the head. [Illustration: FIG. 64.—Maxilla of _Eriocephala calthella_: _l_, lacinia; _g_, galea; _mx.p_, maxillary palpus; _st_, stipes; _c_, cardo.—After Walter. ] The second maxillæ are very much differentiated and vary greatly in the different orders, being especially modified in the haustellate or suctorial orders, notably the Hymenoptera and Diptera. In the mandibulate orders, particularly the Orthoptera, where they are most generalized and primitive in shape and structure, they consist of the following parts: the _gula_ (a _postgula_ is present in Dermaptera), _submentum_ (lora of Cheshire, i, p. 91), _mentum_, _palpifer_, the latter bearing the _palpi_; the _lingua_ (_ligula_) and _paraglossæ_, while the hypopharynx or lingua is situated on the upper side. The labial palpi are of the same general shape as those of the first maxillæ, but shorter, with very rarely more than three joints, though in Pteronarcys there are four. Leon has detected vestigial labial palpi in several Hemiptera (Fig. 73). As to the exact nature and limits of the gula, we are not certain; it is not always present, and may be only a differentiation of the submentum, or the latter piece may be regarded as a part of the gula.