1924 ] Phylogeny and Piterrelationships N emaiocerous Diptera 241 
is retained in the family Bibionidse, then Hesperimis must be 
retained in the Bibionidse also. 
The Simuliidse are extremely closely related to the Chiro- 
nomoid family Ceratopogonidse, and apparently represent a 
connecting group annectant between the Chironomoidea and 
Bibionoidea, with some suggestions of affinities with the Culi- 
coidea. The Simuliidse apparently branched off at or near the 
base of the Bibionoid stem. 
The Chironomoidea include the Chironomidse and Cera- 
topogonidse, and possibly the Thaumaleidse (Orphnephilidse) 
also. The Ceratopogonidse branched off from the base of the 
Chironomoid stem, and have retained many characters sug- 
gestive of affinities with the Simuliidse and with the Culicoidea 
also. The Chironomoidea are so closely related to the Culicoidea 
that it might be preferable to include them in the superfamily 
Culicoidea, but for the sake of convenience, the Chironomoidea 
have been treated as a distinct superfamily in the phylogenetic 
tree shown in Fig. 1. 
The Culicoidea include the Dixidse, Culicidse, and Chaor- 
boridse, the latter being usually regarded as a Culicid subfamily, 
the Chaorborinse (Corethrinse). The Dixidse appear to be very 
close to the ancestral stock from which the Culicidse and Chaor- 
boridse were derived. The Culicoidea and their close relatives, 
the Chironomoidea, were apparently derived from ancestors 
very closely allied to the Anisopodid-like ancestors of the Bibio- 
noidea and Mycetophiloidea, so that these Anisopodid-like 
forms were the types from which the Mycetophiloids, Bibionoids, 
Chironomoids and Culicoids were derived. 
The Blepharoceroidea, containing the single family Blepha- 
roceridse, represent an extremely isolated ‘‘compact” group 
whose affinities are very difficult to determine. Of the three 
Blepharocerid subfamilies Edwardsininse, Blepharocerinse, and 
Deuterophlebinse, the Edwardsininse, represented by the genus 
Edwardsina, are the most primitive; but even with the help of 
Edwardsina, it is practically impossible to determine the closest 
affinities of the Blepharoceridse, for despite Edwardsina’ s prim- 
itiveness, it is extremely isolated, and is not approached at all 
closely by any Nematocera I have seen. I find in the Blepha- 
