. Bulletin of the Department of Agriculture. Agriculture. TRANSFORMATIONS OF BUFFALO GNATS. 17. Fig. 13. -Simullum vittatum. Labial plate of larva. Greatly enlarged. (Original.) those borne on the third segment of the antenna. The lacinia bears mesad and cephalad fringes of long hairs and bristles. On its distal end there is a single spurlike process. The labrum is short, rounded, fringed with long hairs, and is situ- ated overhanging the hypopharynx. It is reinforced on its dorsal sur- face by a strong T-shaped sclerite. The apical mar- gin is sometimes serrate. The labium (figs. 4, 5, 9
. Bulletin of the Department of Agriculture. Agriculture. TRANSFORMATIONS OF BUFFALO GNATS. 17. Fig. 13. -Simullum vittatum. Labial plate of larva. Greatly enlarged. (Original.) those borne on the third segment of the antenna. The lacinia bears mesad and cephalad fringes of long hairs and bristles. On its distal end there is a single spurlike process. The labrum is short, rounded, fringed with long hairs, and is situ- ated overhanging the hypopharynx. It is reinforced on its dorsal sur- face by a strong T-shaped sclerite. The apical mar- gin is sometimes serrate. The labium (figs. 4, 5, 9, 13, 14), which almost covers the ventral surface of the hypopharynx, is composed of two or more broad chitinous united plates. It is immovable. The apical edge of the ventral plate is serrate. The lateral and apical margins of the dorsal plate are also serrate and the apical margin usually bears a very prominent central tooth. In some species the teeth are trifid, and in others simple. There is a row of from three to 10 long bristles near each lateral margin of the ventral plate. The number and shape of the teeth and the arrangement of the bristles are of systematic value in separating the different species, and Robaud and Malloch1 consider these char- acters to be of possible generic value. There is a certain amount of in- dividual variation, but seemingly within defi- nite limitations. The dorsal portion of the head in most species has distinct markings of very characteristic arrangement. (PL IV. figs. 1-4.) Though sub- ject to a certain amount of individual variation, they are of systematic value in separating; the different species especially when combined with other more con- stant specific characters. These markings are formed by a collection of large cuticular cells which, in some species, such as S. vittatum, are strongly pigmented, while in others, such as S. venustum, they are normally almost devoid of pigment, the surrounding area being Please note that thes
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