radical joint in their enumeration, while others have overlooked it, or regarded it merely as a point of support to the palpus. Although frequently almost lost in the substance of the labium, this joint appears however to be always present, and although apparently three-jointed, the palpi must therefore be regarded as really composed of four articulations, (Plate VI. fig. 6, c, c.)
The tongue, (lingua,) generally a very obscure member of the oral appendages, is very distinct in some of the insects of this order. It is short, retracted within the mouth, rather of a soft substance, and in some instances, as in Blatta and Locusta, it bears a pretty close resemblance to the tongue of a vertebrate animal.
The modifications of the antennæ will be specified afterwards as aiding in the discrimination of the different groups. In general they are long, setaceous, and extremely flexible, consisting of fourteen, sixteen, or twenty-five joints among different species of Locustæ; of above thirty among the Mantes; while in the Blattæ or Cockroaches, the articulations sometimes amount to 150, and vary even in individuals of the same species.
Besides the ordinary compound eyes, which in general are large and prominent, the insects of this order are mostly provided with three simple eyes situated in the crown of the head. In the genus Blatta, the domestic cricket, and some other instances, these auxiliary organs are wanting, but there is a subdiaphanous space over the base of the antennæ
