THE CANADIAN ENTOMOLOGIST 45 



correlated with antennal atrophy (atrophy practically only of the 

 third joint, and consequent loss of olfactory function). 



As correlated in importance with facial plate specialization 

 among external adult characters but of less value, it is interesting 

 to note that excessive macrochaetal development has taken place 

 in several stocks and probably by parallelism. The following 

 groups, arranged by families, exhibit spinose-macrochaetal speci- 

 alization: — Hystriciidae, the climax of all (Dejeanini, Saiindersiini 

 pt., Hystriciini, and Larvaevorini pt.) ; Masiceratidae {Blephari- 

 pezini, Belvosiini pt.) ; Exonstidae (Pyrrhosiinae pt. — Tropidopsis 

 and Paragymnomma); Dexiidae (G.-U. s. Echinodexii(E,Tropido- 

 dexiicB); Megaprosopida (G.-U. MegraprosopicB); Phasiidae (G.-U. 

 AmphiboliicB) . 



The wisdom of separating the MegaprosopidcE from the Dexii- 

 dcB and of maintaining them on a par with and more allied to the 

 Oestridae may be questioned. It may be argued that the presence 

 of macrochaetae allies them more with the Dexiidae. We know, 

 however, that their maggots are of peculiar structure, that of 

 Microphthalma at least being quite thickly clothed with long 

 bristly hairs and representing the extreme development of bristly 

 vestiture in the first-stage maggots so far as known, while its 

 cephalopharyngeal skeleton is of a distinct type from the dexiid. 

 Their uteri are of markedly different type from the form typical 

 of the DexiidcB, being known to be very long and irregularly coiled 

 in both Microphthalma and Megaprosopus. Their segregation is 

 thereby demanded since these characters strongly reinforce those of 

 the facial plate. The absence of macrochaetae in the oestrids is due 

 to their aerial life-habit, which is not shared by the Megaprosopids. 



It is possible, notwithstanding the facial and oral characters, 

 that the Trixodini may be found on investigation of their repro- 

 ductive system and first-stage maggots to belong with the Dexiidce 

 rather than with the Megaprosopidae. They almost certainly have 

 a uterus of the continuous-canal type and it is quite possibly 

 of the fat and shortened dexiid type, but the final test of family 

 position here will lie in the type of pharyngeal sclerite possessed 

 by the first-stage maggot. These flies are very rare, at least in 

 collections. The only known specimens are two collected by my- 

 self on tree-trunks in the mountains of the Rio Gila headwaters in. 



