182 INTRODUCTION 
numerous groups with a thick membranous proboscis and broad end-flaps, there 
are forms with a long proboscis projecting far forwards and pointed end-flaps. 
Muscidae of this sort are sometimes voracious blood-suckers, as for example 
Stomoxys calcttrans; others, such as the species of Scafophaga, which possess a 
similar proboscis, live upon excrement, but also suck flowers and kill other insects. 
The proboscis of flies is at least as complicated and efficient an apparatus as the 
suctorial tube of bees. Since the large majority of Muscidae possess a membranous, 
more or less thick and long proboscis provided with broad end-flaps, and adapted 
for feeding upon moist substances, whether of vegetable or animal nature, we can by 
no means regard the family as mainly anthophilous. The more regular flower 
visitors belong more or less exclusively to the following sub-families only:—Phaszneae, 
Ocypterineae, Gymnosomineae, Phanineae, Tachinineae, Dextneae, some Sarcophagineae 
(Onesia, Sarcophaga), Musczneae (Graphomyia, Calliphora, Lucilia, Cyrtoneura), U/z- 
dineae (Ulidia), Anthomyzae (Aricia, Spilogaster, Anthomyia), Sca/ophagineae, Trypetineae 
(Acidia, Trypeta, Urophora, Myopites, Oxyphera, Tephritis), Sepsineae, Chloropineae 
(Chlorops), and some Drosophilineae; the visits to flowers that are paid by species 
belonging to the remaining twenty sub-families are scarcely worth mentioning. 
In the mouth-parts of individual flower-visiting species belonging to the great 
family of Muscidae indications are found of increased specialization in the selection 
of flowers (e.g. in Prosena, Myopites, Ensina, and some species of Tephritis), but 
such cases are exceptional and by no means the rule. Taking the behaviour of the 
Muscidae in general, it appears that ability to pollinate with correlated bodily 
structure occurs quite irregularly in the individual sub-families, so that these insects 
must be regarded as allotropous flower visitors. 
The same holds true for the Lmpzdae (op. cit., p. 113), which in their mode of 
life show a relationship to other predaceous flies (Asz/édae, Therevidae, Lepitdae). 
The proboscis is sometimes short, sometimes elongated. It projects horizontally 
forwards (Hybos), or is curved back (Rhamphomyia), or is directed perpendicularly 
downwards (species of Empis). Species of Rhamphomyia and Empis appear 
as visitors of flowers that only suck and do not eat pollen, and the males of species 
of the latter genus suck nectar, while the females in addition feed by sucking 
other flies. 
The bloodthirsty Zadéanddae possess a thick proboscis, often extended forwards, 
and distinguished from that of other blood-suckers by its broad end-flaps. In 
Tabanus it is once more the males which specially devote themselves to sucking 
flowers, while the females as a rule draw blood from horses and cattle. Here too 
there are in addition to forms that are exclusively blood-suckers (Chrysops, and 
others), individual genera (Silvius, Pangonia) of which the species (at least the males) 
are exclusively anthophilous. 
The Conopidae only suck nectar. The proboscis may be of considerable length 
(in Occemyia), enabling nectar-yielding Papilionaceae (such as Trifolium) to be 
plundered. They confine themselves almost exclusively to flowers with completely 
concealed nectar. As they suck while holding firmly with their feet, social flowers - 
are visited with marked preference. 
Although the family of the Bee-fiies (Bombylitdae) includes short-tongued forms 
(Lomatia, Anthrax, Argyromoeba) with a decided preference for flowers with exposed 
