1915] The Head and Mouth-Parts of Thysanoptera 49 
the mouth and continues dorsad of the pharynx as the oesopha- 
gus (oe.). Transverse sections of the pharynx show that it is 
firmly connected on its caudo-lateral aspects with the maxillary 
guides (mx. g.) and the mesal extensions (et. and 1. et.) from the 
lateral margins of the maxillary sclerites and the labium. 
Over the lateral extensions (et.) the maxillary sete (mx.) pass. 
The left mandible (1. md.) passes over an extension on the 
left lateral margin of the pharynx cephalad of the above 
extensions and the right, rudimentary mandible (r. md.) 
unites with the right margin of the pharynx. The above 
extensions and supports that connect with the pharynx serve 
to hold it in position while the large muscles are dilating its 
elastic membrane (e.). The above facts in regard to the 
pharynx hold for all thrips as far as observed. 
Heliothrips femoralis——Figures 38-46 and 58 give a much 
better idea of the general structure of the pharynx of Helio- 
thrips than a lengthy discussion, consequently only the im- 
portant and exceptional facts will be pointed out. The trans- 
verse sections (fig. 37-44) begin with a section thru the com- 
missures between the supraoesophageal and suboesophageal 
ganglia and end at the tip of the mouth-cone. Every second or 
third section, ten microns in thickness, has been figured. In 
this series the lumen (1.), lateral extensions (et. and 1. et.), 
piercing organs (mx., 1. md. and r. md.), elastic membrane 
(e.), and muscles (d. m.) are shown. The connection of the 
muscles along the meson of the elastic membrane is character- 
istic of the Terebrantia. The large nucleated and cross- 
striated muscles, the dilators of the pharynx (fig. 58, d. m.), 
extend cephalad into the cavity of the head-capsule and unite 
with the ventral and cephalic areas. Two or more of these large 
muscle bands unite with a more or less chitinous tendon 
(c. t.) which arises from the elastic membrane. Besides these 
long muscles a number of short muscles extend between the 
small ventral portion of the pharynx and the clypeus. 
The food of thrips is of a liquid nature and is sucked into the 
oesophagus in the following manner, judging from the structure 
of the parts. The muscles along the meson of the elastic 
membrane contract and dilate the lumen of the pharynx so 
that a partial vacuum is formed, and into this cavity is sucked 
the juice in which the tip of the mouth-cone is tmmersed. On 
