. Bulletin. Natural history; Natural history. 170 therefore be considered as amphipneustic does not seem to have much • weight with those who follow this dichotomic arrangement. Perip- neustic larvae occur in Dolichopodidae and vestigial spiracles are pres- ent in some Strayiomyiidae—facts which point, not to the more primi- tive nature of the species possessing these organs but to the persistence of the latter because of their utility in the larval habitat. There must be a further division of the tribes in Diptera, but until we have data upon a larger number of species in the order any propos
. Bulletin. Natural history; Natural history. 170 therefore be considered as amphipneustic does not seem to have much • weight with those who follow this dichotomic arrangement. Perip- neustic larvae occur in Dolichopodidae and vestigial spiracles are pres- ent in some Strayiomyiidae—facts which point, not to the more primi- tive nature of the species possessing these organs but to the persistence of the latter because of their utility in the larval habitat. There must be a further division of the tribes in Diptera, but until we have data upon a larger number of species in the order any proposed subdivision, including that of the present paper, must neces- sarijy be merely tentative. I give a figure of a hypothetical genealog- ical tree of Orthorrhapha which illustrates my opinion of the re- lations of the various families (Fig. i). There are defects in the scheme that will probably be obvious to many, and it remains for some future worker to improve on the suggestion here given. The sequence of families in this paper is according to the author's ideas, differing somewhat from that in Williston's "Manual", but subject to amend- ment upon discovery of new data. Culicitlae CeraiopogoiiiUae Orphnephilidac. Chiroiioinitlae Platyiiridae Sciaridae Fig. 1. Hypothetical genealogical tree of Nematocera, illustratiug the grouping in this paper. The nervous system as a means of identification may be elimi- nated because of its limited applicability—in preserved material—but we may with little reserve accept as one of the primary indices to affinities the nature of the respiratory system. Insects normally breathe by means of thoracic and abdominal spiracles, and these are found in the adults and in a great majority of the pupae of the Diptera. It is the exception, however, to find them in the larvae, and as a means of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and app
Size: 2113px × 1183px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
