554 HEMIPTERA. 



increased rapidity. Soon this pulsation becomes so rapid that 

 several contractions may be counted in a second. However, 

 we must turn our attention elsewhere, for the whole digestive 

 tube is now in the most lively peristaltic movement, filling it- 

 self rapidly with blood, as is easily observed ; the long oesopha- 

 gus is particularly agitating, throwing itself from one side to 

 another inside the neck, bending itself so violently as to re- 

 mind one of the coiling of a rope when being shipped on deck." 

 Schiodte states that the sucking organ or beak is a "dark 

 brown protruding haustellum, provided with hooks at each ex- 

 tremity, out of which an excessively delicate membranaceous 

 tube, of varying length, is hanging. This pumping "ventri- 

 cle" (which is undoubtedly homologous with the pumping 

 stomach of most sucking insects, such as the Diptera, Lepiclop- 

 tera and Hymenoptera) Schiodte has discovered in "those 

 Coleopterous larvae which have powerful organs for biting, 

 placed at a distance round a very minute 

 mouth-opening, such as the larvae of Carabi, 

 Hydrophili, and Hister, as well as in the 

 larvae of Dytisci, which suck through the 

 mandibles." 



The same author also shows that the mouth 

 Fig. 559. of Pediculus differs from that of Hemiptera 



generally in the circumstance that the labium is capable of 

 being retracted into the upper part of the head, which there- 

 fore presents a little fold, which is extended when the labium 

 is protruded. He also shows that those parts which were, by 

 mistake, thought to be palpi and mandibles by Erichson, 

 Jurine and Landois, are simply lobes on the under side of a 

 chitinous band. 



In Pediculus the thorax is a little smaller than the elongated 

 abdomen, and all the tarsi are two-jointed. The genus PJitJii- 

 rius has a very small thorax, with the abdomen much wider 

 than the head, and the fore tarsi have but a single joint. 

 Plitliirius pubis Linn. (Fig. 559), the Crab louse, is found on 

 the pubic region of man and also on the head. 



MALLOPHAGA Nitzsch. The Bird-lice live on the hair of 

 Mammalia and feathers of birds. In this group there are dis- 



