THYSANURA.— PEDICULINA. 363 



The Thysanura (Jjepisma, Ca?npodea, Japyx) resemble 

 the young JBlattoe. They have ten well-marked abdominal so- 

 mites (Campodea, Fig. 102), and the gnathites conform to 

 the mandibulate type. The abdomen in Machetes has a pair 

 of elongated cylindrical appendages attached to every seg- 

 ment except the first ; while Campodea and Japyx have seven 

 pairs of such abdominal appendages. 1 



The Collembola are provided with a curious tube or sucker, 

 which is attached to the sternum of the first abdominal so- 

 mite, and gives exit to a glandular process, which secretes a 

 viscid matter. Most of the insects belonging to this group 

 possess a curiously-contrived " spring and catch " attached to 

 the sternal region of the penultimate or antepenultimate so- 

 mites of the abdomen, by the help of which they execute their 

 vigorous leaps. 



Sir John Lubbock could find no trace of trachea? in any of 

 the Collembola except Smynthurus, though they are easily 

 seen in many of the Thysanura. According to the same au- 

 thority, Lepisma has four Malpighian tubes, while Campo- 

 dea, Japyx, and many Collembola, have none. 



The 3fallophaga are parasites upon mammals and birds, 

 on the hairs and feathers of which they feed. The head and 

 body are depressed, the eyes simple, the gnathites of the mas- 

 ticatory type. The abdomen has nine or ten visible segments. 



The Pediculina, or Lice, subsist upon the blood of the 

 mammals on which they are parasites. The gnathites are 

 converted into a piercing and sucking apparatus. The under- 

 side of the head presents a soft protrusible proboscis, pro- 

 vided externally with minute horny hooks, and traversed by 

 a canal which leads into the oesophagus. The proboscis in- 

 closes two grooved chitinous styles, which are applied to- 

 gether by their concave sides ; and, within the sheath thus 

 formed, lie two finely-pointed chitinous setae, which can be 

 moved up and down in the sheath. 2 



The proboscis is, in all probability, formed by the union 

 of the labrum with the second pair of maxilla?, while the tw r o 

 halves of the horny sheath are the mandibles, and the setae, 

 the first maxillae. The prothorax, mesothorax, and meta- 



1 The myriapod Scolopendrilla has similar appendages attached to each 

 segment along with legs. (Lubbock, I. c.) 



a Gerstfeldt, " Ueber die Mundtheile der saugenden Insecten," 1853. 



