MALLOPHAGA. 555 



tiuct jaws. The flattened body is corneous, hard above, and 

 the head is horizontal, with three to five-jointed antennae ; the 

 eyes are small and simple ; the mandibles are small, like a 

 hook, and the maxillary palpi, when present, for they are some- 

 times wanting, are four-jointed, while the labial palpi are two- 

 jointed. The thorax is small and but two-jointed apparently, 

 as the meso- and metathorax are united together. The abdo- 

 men is from nine to ten-jointed, while the short thick limbs 

 have two-jointed tarsi and one or two claws. 



Nearly every mammal and bird has its special mallophagous 

 parasite, so that the number of species is actually very large. 



These insects are considered by Burmeister as forming a 

 passage from the Hemiptera into the Orthoptera, as they pos- 

 sess free biting mouth-parts, especially free mandibles, which 

 are not as in the rest of the suborder fused together with the 

 other parts to form a sucking tube. 



In the genus Pliilopterus of Nitzsch the antennae are fili- 

 form, five-jointed, and the labial palpi are wanting. Nirmus 

 is an allied genus ; both live on birds. 



Tricliodectes canis DeGeer lives on the dog, and has three- 

 jointed antennsa, and the tarsi are provided with a single claw. 

 The females have two movable hooks on the penultimate ring 

 of the abdomen. 



In the genus LiotJieum and allies, the antennae are club- 

 shaped, four-jointed, and the labial palpi are distinct. Lio- 

 tJieum anseris Sulzer lives on the goose and swan. 



Gyropus has no labial palpi ; there is a single tarsal claw for 

 clinging to the skin of its host. Gyropus porcelli Schrank is a 

 third of an inch long and lives on the Porpoise. 



Fig. 5G0. 

 LcemopJilceus adusius 'Lee, a Cucujid; see p. 446. 



