7 
ATTACHMENT OF THE ABDOMEN TO THE THORAX 
IN DIPTERA! 
BENJAMIN P. Young 
Many excellent studies have been made by various investigators on 
the morphology of the thoracic sclerites of different groups of insects. 
A number of these investigators have covered the entire class Insecta 
with the hope of determining the ground plan on which a typical thoracic 
segment is based. Such investigators have done much toward estab- 
lishing a uniform terminology for this particular part of insect anatomy. 
Other workers have limited themselves to the consideration of a smaller 
group, as the order or the family. But in no place in the literature has 
the writer been able to find a record of extensive studies on the order 
Diptera. Snodgrass (1909, a and b) and Crampton (1909) have each 
figured two species; others have made even briefer references to the 
group. As for comprehensive work on the relation of the anterior 
abdominal sclerites to those of the metathorax, nothing has been found, 
isolated text figures being the only contributions along this line. 
Through this study, which had as its primary aim the homologizing 
of the abdominal and thoracic sclerites in species of each available family 
of the Diptera, it was hoped that something might be added to the mor- 
phological literature of the group. Among the indices to phylogeny, 
wing venation has come to be regarded as one of the most valuable because 
it is the most evident; the morphology of the genitalia has not been used as 
much because of the difficulties attending such studies, but at present it 
is gaining favor because of the desirability of using all available means 
in throwing light on the above-mentioned problem. Vestiture has been 
made use of, especially by dipterologists, but mostly for generic and specific 
characters. If the external morphology of this particular part of the 
exoskeleton can contribute but its share toward the history of the descent 
of the group, the writer will feel that his efforts have not been in vain. 
Furthermore, systematists of the order are not in accord as to the 
1 This investigation was suggested by, and carried on under the direction and supervision of, Dr. O. A. 
Johannsen. The writer is indebted to him not only for many suggestions growing out of his experience 
pach the order Diptera as a whole, but also for his sincere interest shown throughout the progress of 
the work. 
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