VARIOUS DIPTERA i8i 



beak-like prolongation of the head in Syrphidae, which is correlated with an enlarge- 

 ment of the cavity for receiving the proboscis. 



' Among purely suctorial flies, the species of Empis carry their thin, straight 

 proboscis directed downwards, and prefer to use it in that position. They therefore 

 chiefly resort to erect flowers, into which they can plunge this organ vertically down- 

 wards. If the flower is tubular, and so much elongated as to make it necessary, they 

 thrust the whole head down into the tube, an action which its small size renders 

 possible, even when the tube is tolerably narrow. The chitinous piece formed by 

 coalescence of the mandibles is broadened (e.g. in Empis tesselaia) into a sharp, 

 lancet-shaped plate, which, guided by the elliptical end-flaps, is used for boring into 

 juicy tissue, such as the inner wall of the spur in species of Orchis. Any consider- 

 able increase in length in a downwardly-directed proboscis is clearly impossible 

 without the development of a joint. 



'In the Conopidae, when the proboscis, which is still carried downwards, is of 

 considerable length, it is bent like a knee at its base or in the middle. In the latter 

 case the distal part folds back into the proximal, like the blade of a pocket-knife, 

 thus enabling the proboscis still to be carried in a downward position. 



' The species of Bomhylius, on the other hand, carry their proboscis (which here 

 also is too long to be carried downwards without folding) directed straight forwards, 

 and permanently ready for action. They thus obviously save time, for, without 

 settling, they are able to insert the proboscis into nectar-yielding flower-tubes as they 

 hover in the air, flying rapidly from one blossom to another. In length of proboscis 

 they rival Rhingia, for in Bomhylius major this organ is lomm. long, and in B. 

 discolor ii-i2mm. They also approximate to Rhingia in their powers of detect- 

 ing deeply concealed nectar. The species of Bomhylius, like those of Empis, are 

 also able to bore into succulent tissues. For the labium and the labrum which it 

 encloses are gutter-shaped, and together form a tube in which the bristle-like 

 maxillae, with the broad, strong, and pointed mandibular piece, move backwards 

 and forwards. The labrum itself is drawn out into a stiff and extremely fine point. 

 All these piercing structures, held between the long, narrow end-flaps, can easily 

 penetrate soft tissues. I have often seen species of Bomhylius thrust their proboscis 

 into nectarless flowers (e. g. B. canescens Mik. into Hypericum perforatum), and 

 I imagine that here the boring-apparatus was being brought into action. 



'While, so far as I know, the species of Bomhylius and the Conopidae seek 

 only the juices of flowers, very many other anthophilous flies are in the habit at 

 times of sucking all kinds of other fluids and damp substances, these often being of 

 uncleanly nature. Species of Eristalis, for example, may often be seen feeding 

 eagerly in gutters, and species of Scatophaga and Lucilia on dung. Sarcopkaga 

 licks putrid flesh with relish, and even Volucella bombylans, so common on flowers, 

 I noticed (in May, i860) feeding on a floating carcase, returning repeatedly to it 

 when driven away.' 



To this account by Hermann MuUer, E. Loew (' Blumenbesuch,' II, pp. 1 1 1 

 et seq.) adds that the mode of life and the structure of the proboscis in the great 

 family of the Muscidae are extremely varied. This investigator, who has studied with 

 particular care the structtire of the insect proboscis, states that, in addition to 



