690 CLASS IV. INSECTA. 



number of its stigmata and in its wing nervures, but its ovipositor is curved 

 downwards and not backwards, and its antennae have 8 segments. 

 Thrips, Limoihrips. 



These two families are sometimes known as the Terebrantia. 



Fam. 3. Phloeothripidae. No wing nervures or at most one longitu- 

 dinal one ; antennae with 8 segments ; body flat and last abdominal 

 segment tubular. Phloeothrips ; Anthothrips. 



This family is sometimes known as the Tubulifera. 



Order 14. HEMIPTERA * (RHYNCHOTA). 



Mouth parts form a jointed beak or proboscis bent backwards 

 under the thorax ; wings with rare exceptions four, the anterior pair 

 either half horny and half membranous, in repose lying flat on 

 the back (Heteroptera), or of the same consistency throughout 

 and sloping over the abdomen (Homoptera). Little metamorphosis. 



A very variable and very large order, which includes bugs, 

 plant-lice, scale-insects, etc. Some 20,000 species are already 

 known, of which about two-thirds are Heteroptera. The mouth- 

 parts are the truest mark of a Hemipteron, and their form is 

 constant in the two great sub-orders Homoptera and Heteroptera, 

 though these insects differ profoundly in other respects. The 

 mouth-parts consist firstly of a tubular or rather grooved process 

 formed from the labium ; this may consist of one, two, three or 

 four segments and is, when at rest, bent back under the thorax. 

 It is devoid of palps and probably represents only the 2nd 

 maxillae. The proximal portion of the groove is covered by a 

 triangular labrum, but this does not extend far along the groove. 

 If it be raised the remaining mouth parts can be seen lying in 

 the groove. These consist of four chitinous setae capable of being 

 protruded beyond the end of the groove, and they form the 

 piercing organs of the insect. The outer stylets are usually 

 regarded as representing the mandibles and the inner the 1st 

 maxillae which like the 2nd are without palps. This view 

 however is combated by some authorities. The stylets un- 

 doubtedly act as piercing organs, and the juices of animals or 

 plants ascend the tube perhaps by capillarity or by the action 

 of a sucking pharynx (Fig. 375). 



The head varies greatly in shape and in some families is quite 



* Schiddte, Ann. Nat. Hist. (4), vi, 1870, p. 225. Ashmead, Entom. 

 Americana, iv, 1888. Saunders, Hemiptera Heteroptera of the British 

 Isles, 1892. Pascoe, Ann. Nat. Hist. (5), ix, 1882, p. 424. Stal, Hemiptera 

 Africana, 1866. Edwards, Hemiptera Homoptera of the British Islands, 1896. 



