250 THE AMERICAN NATURALIST. [VoL. XXXII. 
form will be found among the living representatives of this 
order. We have now to consider modifications of this type in 
representatives of the suborder Heteroptera. 
In our studies of Heteroptera we have examined nymphs of 
the following families: Notonectide, Nepidz, Belostomidz, 
Reduviidee, Nabidz, Capsida, and Pentatomidz. Of these 
_ there is no doubt that the most generalized condition of wing 
venation is found in the family last named, but further studies 
in other families may reveal a still more primitive type. 
Fig. 21 represents the tracheation of the fore wing of a 
Fic. 21.— A Pentatomid, fore wing, nymph. 
Pentatomid nymph. In this wing the costal trachea is well 
preserved. The subcostal and radial tracheæ are closely 
approximate in the basal half of the wing; in the distal half of 
the wing the subcostal trachea traverses that part of the wing 
which would be traversed by trachea Ri were it well developed 
and in its typical position; but it is reduced to a rudimentary 
condition. It is evident that a supplanting of Ri by the sub- 
costa takes place here, as in Cicada. The trachea that precedes 
the radial sector has its characteristic bend at the base, and is 
two-branched. The medial trachea is typical, that is, four- 
branched. The cubital trachea is six-branched; it is evident 
that a specialization by addition has taken place here. Only a 
single anal trachea has been preserved. | 
