ATTACHMENT OF THE ABDOMEN TO THE THORAX IN DIPTERA 275 
near the middle of the segment, if anything slightly cephalad from the 
center. Such an arrangement as that in Oncodes incultus (Plate XVI, 23), 
in which the first abdominal spiracle appears in the posterior part of the 
“segment, is very unusual, while examples of the shifting of all spiracles 
to the anterior end, as in Allognosta fuscitarsis (Plate XV, 19), is not 
at all uncommon. 
SPECIES OF ANTHOMYIDS 
Because of the uncertain systematic position of some genera within 
the family Anthomyiidae, species of twelve genera of this family were 
studied and figured (Plates X XII, 42, XXIII, and XXIV, inclusive). Con- 
siderable uniformity is shown in the structure of the region around the 
base of the abdomen. In each case were the episternum (es’) and the 
epimeron (em*), as well as the pleurotrochantin (ptn*), of the metathorax 
clearly defined. The fused condition of the first and second abdominal 
tergites, in contrast to the separate state of the corresponding sternites, 
held in each. Also, the adventitious suture of the first abdominal tergite 
was constant. The greatest variation found in these species, perhaps, 
was in the location of the abdominal spiracles. This can be seen by 
referring to the information concerning abdominal spiracles which ac- 
companies each species in the list on pages 258 to 261. 
SUMMARY? 
Points brought out in a summary of an investigation of this nature must 
of necessity be based upon a study of a rather limited amount of material, 
considering the number of genera and species in the entire order. How- 
ever, uniformities existing in single species of so wide a range of families 
as the writer has been permitted to examine, will at least suggest points 
to be tested in a wider range of species within certain families. Further- 
more, they cannot help adding their bit in the task of unraveling the phylog- 
eny of the order Diptera. 
One of the most interesting characteristics to appear in a large number 
of families is what has been termed an adventitious suture, or a suture 
running caudo-dorsad from the anterior margin of the first abdominal 
_tergite and one not to be confused with the suture dividing the first and 
the second tergite although the two are closely related to each other. 
2The chart from which this summary was deducted is inserted at the end of this paper. 
