38 TIIIC CANADIAN ICNTOMOLOGIST 



than is the farinl plate. Siihtrihal to subfamily shf)iild ho attributed 

 to the characU'is ol (he rcprochictive system, ('KK>' and lirst-sta^e 

 maj^JK"*^. with family values imder certain eireumslances. When 

 the true or in< iibatinjj uterus is present its main type is a character 

 of liii;h \ahic. The si incline ol I he e^^-chorion and certain 

 slriicliir.il delails ol llie rirst-sta}>e maggol are characters of still 

 hij^her value. When such cliaraclers as these are sui)porled by 

 others they may well be used in famil\- defniilions. rractically 

 all the early-stage, egg and reproductive - system charac- 

 ters are especially important and serviceable lo us as indicating 

 posili\'el\' I he naliiial limits of taxonomic" groups, whereby we can 

 with cerlainl\ diav\ a lixed line between those groui)s whose 

 individual forms often can not be separated on (he external adult 

 characters. 



A classilicalion ol ihe Muscoidea inio family divisions founded 

 on llie general characler ol (hei'gg, whel her elongate-subcylindrical 

 or 1 1. 1 1 (eiied ()\ ale, is (|iiile oul ol (he (pieslion considering the exter- 

 nal iharacters of (he Hies themselves; one founded on elongate 

 uteri, or (hi' absence of uterus, or on maggots developing in (he 

 uterus, would result similarly in an artificial and unnatural grouj)- 

 ing. This ma>' be realized b\' s(iid>'iiig the t.ibular summary a( the 

 end of (his |)aper. Iiu( (here are cerlain otlu-r characters ex- 

 hibid'd here (hat will ai)pl> to lainily divisions. l'^)r example 

 the old famil>' Sanol>h(i<!_id(ie may well be restored in a new sense 

 on the characters ol the cordate .ind V shaped uterus, both types 

 being .i double-sac speciali/alion ol the ii(ei"o\agiiia (|uile distinct 

 in character hom all the other lornis ol lUeiine si)i'riali/al ion in 

 the Muscoidea. This division is st reiigl lu'iied b\' the generalized 

 cliaractei- of the cephalopharNnge.d skeleton in the (irst-stage 

 maggot of most ol the lorms, .ind b>' (h(> deepb-sunki'ii anal- 

 stigmatic ca\il\ of all (he ni.iggol stages, hanploying the uti-rine 

 character it becomes now lor the liist (line possible (o derme posi- 

 tiveb and .icciiia(el\ (lie limits of this l.imily. 



It now seems i'(|nall\' di'sirable to restore the old l.nnily Prxi- 

 idac, bill in a new sense-, on a lombin.il ion ol lacial plate and ac- 

 cessory suppoiting chaiack'is, detiniteK limiled \>\ (he re|)ro(liu(i\-e 

 and especially by (he lirs( stage cephalophar\ngi'al characters. 

 This is a n.idiral groii]) intermediate in facial-plate exolution 



