No. 374.] . THE WINGS OF INSECTS. 89 
the radial trachea tends to follow the base of the medial in its 
migration along the transverse basal trachea towards the cubito- 
anal group (Acrididz). 
We have found no indication that the formation of a trans- 
verse basal trachea and the subsequent migration along it of 
the base of the medial trachea is influenced at all by the flight 
function of the wing, as the arrangement of the wing-veins does 
not appear to be modified by it. It should be remembered that 
the transverse basal trachea and the bases of the wing tracheze 
are within the thorax of the adult insect, and are thus beyond 
the influence of the migrations of the wing-veins. 
It is probable that these changes have to do with improving 
the air supply of the wing; but we have not sufficient data, as 
yet, to warrant a definite statement on this point. The impor- 
tant thing for the purposes of the present discussion is that 
one must know of this tendency on the part of the medial 
trachea to migrate along the transverse basal trachea in order 
to be able to recognize it in its various positions. 
ENTOMOLOGICAL LABORATORY, 
CORNELL UNIVERSITY, December, 1897. 
