300 DESCRIPTION OF THE PLATES. 



g. The first of the ten somites composing the abdomen. The ventral 

 surface of each, except the first, bears a pair of setose cylindrical 

 appendages. The last pair is large. They are moved by the animal 

 as it runs. 



In Lepisma saccharina these appendages are present only on the last two so- 

 mites, and are represented on the anterior somites by groups of stiff hairs. In Cam- 

 podea and lapyx they are absent on the eighth and ninth somites. They appear to 

 represent abdominal legs. Such legs are present in many embryonic Insects, and 

 in larval Lepidoptera, Tenthredinidae, and Panorpatae are developed into prolegs on 

 more or fewer of the abdominal somites. It may be noted that in Machilis 

 the female possesses, in addition apparently to the abdominal limbs, two append- 

 ages, on the eighth and ninth somites, which form an ovipositor. As there is no 

 reason to doubt the homology of these processes with the parts of the ovipositor 

 similarly found in many other female Insecta, their homology with limbs appears 

 doubtful, and in need of further elucidation. 



k. Median and 



i. Lateral caudal filaments belonging to the tenth somite. The lateral 



filaments are perhaps homologous with the abdominal limbs present 



on the foregoing somites. 

 j. Last and elongated pair of abdominal limbs. 



Anatomy of a Collembolan. Sommer, Macrotoma plumbea, Z. W. Z. xli. 1885. 



FIGS. 2-4, Mouth-parts of a Tiger-beetle, Cicindela'littoralis. From Stein's figures in Cams, 

 Icones Zootomicae, I, Leipzig, 1857, PI. XIV. Figs. 12-14. 



Fig. 2, The mandible, which consists, as in all Insecta, of a single 

 piece. In this carnivorous biting animal, it is curved, pointed, and its 

 inner edge is produced into four sharp teeth. 



Fig. 3. The maxilla composed of six parts. 



a. The lacinia with a terminal hook which is moveably articulated, and 



distinguishes, among other points, the small family Cicindelidae or 

 Tiger Beetles from the large family Carabidae or Ground Beetles. 



b. Palpiform two-jointed galea, which is distinctive of the tribe Adephaga, 



comprising the families Cicindelidae, Carabidae, Dyticidae, and 

 Gyrinidae among the Coleoptera Pentamera. 



c. The four-jointed maxillary palp, articulated to 

 / The palpiger. This in its turn rests upon 



e. The stipes and 



d. The cardo, which articulates with the skull. 



Fig. 4. The labium. It is much simplified as compared with the 

 labium in Periplaneta. It consists of a transverse basal piece with two 

 notches in the anterior border separated by a pointed process, and repre- 

 sents, according to Professor Westwood, the mentum. Two four-jointed 



