MORPHOLOGICAL STUDIES ON THE HEAD AND 
MOUTH-PARTS OF THE THYSANOPTERA.* 
By ALVAH PETERSON. 
TABLE OF CONTENTS. 
PAGE 
Te | Introdtuc tion wks 0 te1 citar erates ald pei eae ese eee 20 
LE. Methods cas acierts cosink cate sc oak oe Oat eC eee eee 23 
IIs Acknowledgements 5. site ccc seticier ee erate saree ometas ae ener er eereene 24 
IV. Pixed ‘Parts of the’ Heads. ..8 aaa seitacieeinae Cane tere Re eee 24 
Head-capsulle ois \.cracsxd mecewic ies Somme ttn ore sikelele Siekteeie eee eae 24 
Clypeusiand Labriaim. Jy: ar aie etna = cos alee ote eo ee eee 27 
Compounds Byess snared horas ne ee Ree nee ne eee ae 28 
Ocelli ss shore A OC eee EE REGO EEE Le eee Ree 29 
‘Tentorium: or Internal Head-Skeleton=-. nin. 22s05 soe oe oe dee 29 
V.-Movable:partsiof the Head):a.22 thes, moti Sern ree ee eco ea 34 
ANGENTAC Sc cic wae olove # tae oe Pee ch epee re a nae een TORE rene Cree 35 
I eyheba Aeron ares rman MAREN RA Wii ng i er ainn Sabin cringed Gin Goo ot & 35 
Maxi llaes 508 Find tc ae eed seems Coe Sek ermine a Gare eae amin ra ee eee 36 
Mian dibless ss aciciate etivns Seater eae oes Sea eS NS ON ia cae te eon Ree ee 43 
WI |< Phtaryaixens0 saeco aie he ad 2 ie cette CRE ore ECO ae oe a 48 
Wil. Salivary Glandsisi eats) seein wee ett ot eee a eee eee 51 
VITIES sblead=olands 2c: sia eo ie ces eka ete oes ore ee IE 54 
DX Summary: ve sf Macs h Sis eee ea sue efor ene ee ae el feta a ated eae aoe 59 
Mo Biblographyaaec cous temo re Cio ee rata oe oe mes SER eT Pree 57 
INTRODUCTION. 
The small insects of the order Thysanoptera have four 
long, narrow, membranous, flat, fringed wings. Only a few 
veins are present in the wings and when at rest they are laid 
horizontally along the back. The sucking mouth-parts form a 
cone at the caudo-ventral margin of the head-capsule. The 
maxillae, in part, and the left mandible are modified into 
piercing organs and enclosed within the mouth-cone. The 
mandibles, clypeus and maxillary sclerites are asymmetrical. 
The tarsi are two-jointed, bladder-like at the distal end and 
without claws. The metamorphosis is incomplete. 
The order is divided into two suborders, Terebrantia and 
Tubulifera. The more important distinguishing characters 
of these are as follows: The female of the Terebrantia has a 
saw-like ovipositor. This is wanting in the female of the 
Tubulifera. In the Terebrantia the terminal segment of the 
abdomen of the female is conical, while that of the male is 
rounded. In the Tubulifera the distal segment of the abdomen 
is tubular in both sexes. One or more longitudinal veins 
* Contribution from the Entomological Laboratories of the University of 
Illinois, No. 42. 
20 
