424 ENTOMOLOGICAL SOCIETY 



base of the third and to form with the third joint a clasping 

 organ, probably connected with the copulatory act rather than 

 for attachment to hairs. 



The eyes are quite generally reduced, the ocelli usually want 

 ing entirely, and the compound eyes reduced to a small number 

 of facets. In Hippoboscidas the eyes are somew'hat lunate, and 

 of a small number of facets. In Pediculidae the facets are re 

 duced to but one or two, sometimes apparently entirely wanting ; 

 while in Mallophaga. when present, they consist of but one or a 

 few facets. In the Arachnoids they are often entirely wanting, 

 and if present are extremely simple. 



In the mouth-parts there is naturally a great deal of modifica 

 tion to correspond with the habit of procuring food. In 

 Melophagus there is a well-developed sheath, and the suctorial 

 tube is strong and capable of being thrust well into the skin of 

 the host. In Polyctenidse the rostrum is three-jointed, but in 

 PediculidaB the rostrum is reduced to a single joint, while the 

 seta3 forming the suctorial tube are extremely elongated, so as to 

 permit penetration of the skin of the hosts, and this in some of 

 the larger animals means a considerable extension. In the 

 Mallophaga the mouth-parts are not especially different from 

 those of Atropos or Clothilla, but the mandibles are strong, 

 usually bi- or tri-dentate, and the maxillas and labrum are reduced. 

 The Arachnid parasites have either lance-like piercing or cutting 

 mandibles or piercing and suctorial mouth parts. In Ixodidas they 

 are barbed and well adapted for clinging to the body of the host. 

 In Sarcoples the mouth-parts are fitted for cutting, and enable the 

 mite to burrow in the dermal tissue. In Pentastomum, in the 

 adult, the mouth-parts are reduced to mere rudiments. 



The absence of wings in parasitic species is perhaps the most 

 marked degradational character, since it unfits the animal for the 

 mode of locomotion common to the majority of its class. But 

 there are numerous instances where this loss occurs in non- 

 parasitic species, and it can hardly be considered as a result of 

 parasitism except as parasitism means, in most cases, little use for 

 wings. Wings are present in some species of Hippoboscids, 

 totally absent in others, as also in Nycteribiidas, and here the loss 

 of wings seems to follow pretty distinctly the assumption of para 

 sitic habit and the more constant attachment to the host. In 



