THYSANOPTERA. 



689 



Order 13. THYSANOPTERA * (PHYSOPODA). 



Small insects ; the, mandibles are, reduced to stylets and the mouth- 

 parts are lent back under the prothorax ; wings either jour, long, 

 narrow and fringed with hairs, or absent ; tarsi of 1 or 2 seg- 

 ments. Young resemble adults, but there is a pupal instar. 



The usually minute insects, known as Thrips, which constitute 

 this order, are as to their mouth parts somewhat intermediate 

 between the preceding orders and the Hemiptera. As in the 

 last named order these appendages are folded back against the 

 prothorax and the mandibles are reduced to piercing stylets or 

 a single stylet for the right mandible seems to be suppressed 

 concealed in a beak composed of the upper lip and maxillae. 

 Both 1st and 2nd maxillae retain their palps. The antennae 

 are 6-9 segmented. Three ocelli are present in the winged 

 species but absent in the apterous forms. The abdomen has 

 ten segments with stigmata on the 2nd and 8th segments ; the 

 remaining two stigmata are meso- and meta-thoracic. Four 

 malpighian tubes are present. The larvae resemble in form the 

 adults, and eat the same food. Wings begin to appear after 

 the third moult, but the instar preceding the adult is usually 

 motionless and takes no food. The feet have a curious 

 bladder capable of being distended ; it protrudes between the 

 two terminal claws. 



Thrips are said to suck the juices of plants, and undoubtedly 

 some, e.g. the Corn-thrips in Europe and the Onion-thrips in 

 America, do much damage ; other observers think they live 

 on pollen, etc. They are usually found amongst the flowers of 

 plants and are common in green-houses. Some live under bark, 

 some amongst fungi and some cause the formation of vegetable 

 galls which they inhabit. Parthenogenesis occurs. 



The order comprises some 135 species of which 117 are Euro- 

 pean and some 50 British, but as the insects are small many more 

 probably remain to be described. It comprises three families : 



Fam. 1. Aeolothripidae. Antennae with 9 segments ; fore-wings 

 with a few nervures ; an ovipositor of four processes arises from the 

 8th and 9th segments of the abdomen and when extended is bent 

 backwards. Three pairs of stigmata. Aeoloihrips. 



Fam. 2. Thripidae. This family agrees with the preceding in the 



* Uzel., Monog. d. Ordnung Thysanoptero , Koniggratz, 1895. Halliday, 

 Ent. Mag., iii, 1836, p. 439, and iv, 1837, p. 144. 



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