VESTIGIAL WINGS AMONG INSECTS. 185 



Megaspilus sp. indescr. (Proctotrupidae) (Fig. 3). 



In a small subapterous species of Megaspilus is seen the very 

 common phenomenon of a micropterous species closely resem- 

 bling'other fully winged forms. Many other cases of this could 

 be cited among this group of Hymenoptera. 



Apteropompilus (?) sp. indescr. (Fig. 4). 



In a most remarkable nearly wingless species of Pompilidae 

 which occurs in Texas, the venation is more complex than that of 

 Empyris, but much simpler than in other genera of Pompilidae. 

 In this case the wings are very small, being scarcely visible with- 

 out a strong lens and the thorax is narrower than usual, due 

 doubtless to the slight development of the wing muscles. In 

 this family no intermediate forms are known between this and 

 the fully winged species, all of which fly with great activity. 

 Running has taken the place of flight, a tendency which is seen 

 in many of these sand-wasps which are fully winged. 



SECOND CATEGORY. 



The following examples have been chosen to illustrate the 

 condition of wings which are much reduced in size, but still 

 retain very well-defined and distinctive characters. 



1. Mntilla grandiceps Blake, $ (Fig. i). 



This species of Mntilla is a rare exception among the males of 

 this genus of velvet ants, for like the females of all species, it is 

 incapable of flight. Among all the three or four hundred species 

 of this cosmopolitan group, the rule of wingless females and 

 perfectly winged males holds with only two or three exceptions. 

 From the figure it can be seen that the wings are well propor- 

 tioned and still retain the hooks upon the anterior margin of the 

 hind pair. The venation is much confused and not plainly 

 defined. The wings while very small in comparison to the size 

 of the insects (reaching scarcely to the tip of the thorax) recall 

 very strongly the normal wings of certain Proctotrupidae and Chal- 

 cididae where the venation is often completely lost. 



2. Henicopygus snbapterus Ashm. (Chalcididae) (Fig. 6). 



The wings of this insect are very small and evidently useless for 

 flight, but nevertheless have a very distinct venation properly pro- 



