June, '15] BORDEN: IMOUTHPARTS OF THE THYSA^^OPTERA 



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The segments may be short and stout, as in the genus Orothrips, or 

 they may be long and cyHndrical as in many of the genera of the 

 Thripidse. 



Labium. — The labium (PI. 16, figs. 1, a, 7 and 7, a) forms the hind 

 wall of the mouth cone. Where the mouth cone is blunt, the labium 

 is usually ver}^ broad and heavy, and where the mouth cone is sharp, 

 the labium is narrowed. The labial palpi (PI. 16, figs. 1, k and 7, k) 

 are borne near the tip, and the very tip of the labium is lobed and bears 

 a tactile hair on each tiny lobe. There is a strong chitinous bar (PI. 16, 

 figs. 7, a-n) extending down near the median line of the labium which 

 divides near its base and ends in two peculiar, spear-shaped parts. 

 This bar is undoubtedly a strengthening device for the fleshy labium. 

 The labial palpi differ as greatly as do the maxillary palpi within the 

 different families. In the Phlceothripidse they, are usually described 

 as having but one segment and in the Thripidse usually two, while in 

 the famil}" Oelothripidse the genus Orothrips bears five segments and 

 the others but four. In most Thripidse that I have examined there 

 seems to be but a single segment composing the labial palpus. 



Within the hollow^ of this mouth cone we find the maxillary stydets 

 already described, the single mandible on the left side, and an organ 

 which I have taken to be the hypopharynx. 



Mandible. — This is a large, strongly chitinized, styliform organ 

 on the left side (PI. 16, fig. 1, /) and joined by its broad base to the 

 chitinous band in the frons just where the connection is made with the 

 bar running to the left eye. The mandible is peculiarly fitted to this 

 side of the head, and I have been unable to find anything corre- 

 sponding to it on the right side, though several authors have described 

 a rudimentary part. Although the mandible may differ slightly in 

 shape in the different groups, the structure is essentially the same 

 throughout. It is made up of a bulbous chitinous base with a strong 

 muscular attachment and a long sharp stylet slightly angled at its 

 base. 



Hypopharynx. — Just below the mandible and on the base of the 

 mouth opening, viewing the mouthparts from the front, is a large styli- 

 form organ passing through a groove or socket (which is attached to 

 the floor of the mouth opening) and with a strong muscular attachment 

 reaching well up under the frons of the head. This I take to be a 

 hypopharynx. It has been only partially described before. Jordan 

 describes the upper section and suggests that it is a hypopharynx; 

 Buff a describes it in part and also figures an epiglottis; Hinds simply 

 mentions it but does not attempt to describe it. In none of the accounts 

 has it been described as styliform as I have found it in my preparations. 

 This I take to be used much as is the mandible in feeding. 



