TRACHEATA 369 



Hemiptera have a complete metamorphosis ; the adult male has 

 one pair of wings, the anterior, the posterior being replaced by 

 a pair of bristle-like processes, the halteres, as in the Diptera. 

 No mouth is present. 



The female, after the first ecdysis, becomes almost stationary, 

 she retains her proboscis, -which is embedded in the tissues 

 of the plant on "which she lives, as a rule she loses her 

 limbs, and almost all trace of segmentation ; the successive 

 skins that she casts either remain over her body forming a 

 scale, or she secretes a waxy or woolly covering. The eggs 

 are laid under the body of the mother, which ultimately dies, 

 but remains as a covering for her offspring ; under this the 

 young may remain some little time before seeking a convenient 

 place on their plant host to insert their own proboscis. 



Some of the Coccidae are of commercial value, Coccus cacti 

 furnishes the pigment cochineal, and another species produces 

 shellac. Most of the scale insects, however, are injurious to 

 the plants upon which they live, and cause great loss to 

 horticulturists and fruit-growers. Aspidiotus conchiformis is 

 the well-known mussel scale on apple trees, etc., and A. aurantii 

 attacks orange groves. 



Sub-order 3. Parasitica. 



Chaeacteeistics. — These are wingless Hemiptera, commonly 



known as lice; they live as ectoparasites on the skin of 



mammals, sucking their hlood. 



The proboscis is fleshy and unjointed, with, as a rule, a circle 

 of recurved hooks round its base. There are two small simple 

 eyes ; the antennae have five, joints. The legs arise from the 

 edge of the prothorax ; they terminate in a hooked claw, which 

 works against a projection of the tibia; this forms an admir- 

 able apparatus for clinging on to the hairs of their hosts. The 

 young do not undergo any metamorphosis. 



Pediculus capitis is the head louse, and P. vestimenti infests 

 the body of all races of man. It is said that peculiar varieties 

 infest the different races ; thus those that live on negroes are 

 nearly black, whilst the Chinese have a yellowish, and the 

 natives of South Africa an orange variety. The genus which 



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