THRIPS 



529 



metathoracic, Srd on the second abdominal segment, 4th on the 

 eighth abdominal segment.^ There are four Malpighian tubes, 

 and two or three pairs of salivary glands. The dorsal vessel 

 is said to be a short sack placed in the 7th and 8th abdominal 

 segments. The abdominal ganglia of the ventral chain are con- 

 centrated in a single mass, placed in, or close to, the thorax ; the 

 thorax has two other approximated ganglia, as well as an anterior 

 one that appears to be the infra-oesophageal. 



The metamorphosis is also peculiar ; the larva does not differ 

 greatly in appearance from the adult, and has similar mouth- 

 organs and food-habits. The wings are developed outside the 

 body at the sides, and appear first, according to Heeger, after 

 the third moult. The nymph-condition is like that of a pupa 

 inasmuch as no nourishment is taken, and the parts of the body 

 are enclosed in a skin : ' in some species there is power of movement 

 to a slight degree, but other species are quite motionless. In 

 some cases the body is entirely bright red, though subsequently 

 there is no trace of this colour. Jordan distinguishes two 

 nymphal periods, the first of which he calls the pronymphal ; in 

 it the Insect appears to be in a condition intermediate between 

 that of the larva and that of the true nymph ; the old cuticle 

 being retained, though the hypodermis is detached from it 

 and forms a fresh cuticle beneath it. This condition, as Jordan 

 remarks, seems parallel to that of the male Coccid, and ap- 

 proaches closely to complete metamorphosis ; indeed the only 

 characters by which the two can be distinguished appear to 

 be (1) that the young has not a special form; (2) that the 

 wings are developed outside the body. 



Thrips take their food, it is believed, in the same manner 

 as Aphidae, by suction ; but the details of the process are not by 

 any means certain, and examination of the stomach is said to have 

 resulted in finding pollen therein. Walsh thought that Thy- 

 sanoptera pierce and suck Aphidae. An elaborate inquiry 

 by Osborn ' failed to elicit satisfactory confirmation of Walsh's 

 idea, though Kiley and Pergande support it to some extent ; 

 Osborn concludes that the ordinary food is not drawn directly 

 from sap, but. consists of exudation or pollen, the tissues 



1 Jordan in an interesting paper, Zeitschr. wiss. Zool. xlvii. 1888, p. 573, says 

 that in the division " Terebrantia " there are only three pairs of stigmata. 

 - Insect Life, i. 1888, p. 138. 

 VOL. VI 2 M 



