1915] The Head and Mouth-Parts of Thysanoptera 23 
later instars. The term semi-pupa is used in this paper for 
the semi-quiescent instar just before the adult stage and it is 
only referred to in the suborder Tubulifera. 
METHODS. 
For general purposes thrips should be killed in boiling water 
and preserved in 70 per cent. alcohol. When only the chitinized 
parts are desired, living or preserved specimens should be boiled 
for ten or fifteen minutes in a 10 per cent. solution of potassium 
hydroxide, then reboiled in water to remove the alkali, and 
finally preserved in 70 per cent. alcohol. Living material 
treated in the above manner is better than preserved material, 
for preservation in alcohol tends to make the specimens too 
brittle for careful dissection. 
The use of a Leitz binocular microscope made possible the 
dissection of the minute mouth-parts. A number of media 
were tried in which to make dissections; carbol-aniline oil 
proved to be the best. Its good qualities are that it evaporates 
slowly and will clear specimens from any grade of alcohol 
above 50 per cent. If it be desirable to stain with safranin 
or orange G the stain can be dissolved in 95 per cent. alcohol 
and will readily mix with the carbol-aniline oil. 
The staining of the material for dissection with safranin 
proved to be very useful in differentiating the almost colorless 
mouth-parts of some of the species. In using aniline oil in any 
form one precaution must be observed; as much as possible of the 
oil should be removed with a blotting paper or a dry rag or by 
replacing the carbol-aniline oil with carbol-xylene or xylene 
before mounting in balsam. If the oil be not removed the 
media in which the parts are immersed will eventually darken. 
Material for sections was fixed with hot (80° C.) corrosive 
sublimate (saturated corrosive sublimate in 35% alcohol 
plus 2% of glacial acetic acid) for 15 to 30 minutes, which was 
replaced by 70% alcohol containing a few drops of iodine 
for 24 or more hours. 
Paraffin having a melting point of 52-54 C. gave a suf- 
ficiently firm medium in which to cut sections as thin as five 
microns. Erhlich’s and Delafield’s haematoxylins were used 
for staining sections on slides and orange G. or safranin for 
counter-staining. The best results were obtained by staining 
punctured specimens in toto for 24 hours in Delafield’s 
haematoxylin or from 3 to 7 days in borax carmine. 
