as affecting Domesticated Animals. 57 



Pediculi ; Anoplura (Denny). — Lice, 



Under the generic term of Pediculi we recognise those Epizoa 

 commonly known as lico. These parasites constitute the order 

 Anoplura of Denny, being unarmed and without wings. From 

 their great variety they are necessarily divided into several 

 families, genera and sub-genera. 



The primary division of the Anoplura is into the Haustellata 

 (suckers) and the Mandihidata (masticators), of which we have 

 examples in the genus Hamatopinus and Trichodectes which 

 affect domesticated animals. The former of these is easily 

 distinguished by its elongated and narrow head and retractile 

 sucker ; and the latter by its broad and short head and strong 

 mandibles. (See Figs. 8, 10 and 9), which represent the Jhcma- 

 topinns of the horse and the pig, and the Trichodectes of the ox. 



The chief characteristics of lice are that they do not undergo a 

 metamorphosis, have six legs, are without wings, and often also 

 without eyes, or possess two only, which are of simple construc- 

 tion in comparison with those of other insects. 



Although lice do not pass through a regular metamorphosis, 

 nevertheless, in the progress of development from the em- 

 bryo to the perfect insect, they are found to cast their skin, 

 and often more than once, acquiring each time a more com- 

 plete form of the body, and especially of the limbs. In these 

 particulars these epizoa agree with fleas and some other parasitic 

 insects. Kiichenmeister says that " the males are fewer in number 

 than the females ; their last abdominal segment is proininent and 

 rounded off, and furnished on its dorsal surface with a valvular 

 opening, beset with an abundance of asperities, which serves at 

 the same time as an anal opening and poms (jenitalisy 



^' Tlie females, which are more numerous and larger, appear 

 deeply notched at the apex of the last abdominal segment, and, 

 as it were, with two lobes, between which is the anal aperture, 

 Avhich is surrounded with numerous hairs."* 



The two genera, Hcematopinus and Trichodectes, which we 

 have described, not only exist separately, but often together on 

 the same animal ; but hitherto we have only found the Hanna- 

 topinns Suis on the pig, and the Trichodectes Oris on the sheep ; 

 nor does Denny, in his ' Monographia Anoplurorum Britannia*,' 

 allude to any other louse as being met with on either of these 

 animals. 



Whether the pig and the sheep are entirely exempt from 

 all other varieties of lice, we do not take upon ourselves to 

 decide. Asa rule, however, each distinct species of animal has 



* Kiichenmeister on Animal Parasites, vol. ii., p. 77. 



