1935 ] 
Structure of the Pretarsus 
3 
this structure ; de Meijere’s investigations are more exten- 
sive and cover all the important orders but his German 
terminology is not used at all in this country. A complete 
history of the terminology of the numerous parts of the 
claw-segment must be left for a later and more comprehen- 
sive study of this structure, therefore that system accepted 
by the more recent investigators is followed throughout. In 
some cases the same terms are used from order to order, 
even though true homology is not yet proved, instead of of- 
fering new names which in all probability would have to be 
discarded after further study supplied evidence to substan- 
tiate suspected homologies. However, all doubtful cases 
are indicated as such. 
The following is a list of the terms herein used with their 
definitions and equivalents. 
Apodeme (Unguitractor tendon, Sehne). — This is the 
tendon which runs from the unguitractor plate to the tibial 
musculature, the flexor of the claws. Supposedly the claws 
spring back into their normal position by natural resiliency 
when tension through the apodeme is released as there is 
no levator of the pretarsus in insects. (Crampton 1923) 
(Snodgrass 1929). 
Arolium. In general the term arolium is restricted to a 
median paired or unpaired, pad-like structure which is ar- 
ticulated to the unguifer or arises from a position midway 
between the claws. Whether the complicated median struc- 
ture of Hymenoptera, Lepidoptera and Trichoptera, the 
paired ribbon-like parts known as arolia in certain Hemip- 
tera (Miridae), and the single median pad of Diptera and 
orthopteroid insects are all strictly homologous is prob- 
lematical. However, the term arolium is here used to des- 
ignate these structures in every order in which they occur, 
according to the definition above. 
Basipulvilli. (auxillise). This term was first applied by 
Crampton (1923) to the small lateral sclerites at the bases 
of the pulvilli of Diptera and also to similar sclerites lat- 
erad of the unguitractor in Periplaneta although true pul- 
villi are not found in Orthopteroids. The auxillise (Hymen- 
optera), of MacGillivray, are evidently homologous with 
