British blood-sucking flies / by F.W. Edwards, H. Oldroyd, and J. Smart.

  • Edwards, F. W. (Frederick Wallace), 1888-1940.
Date:
1939
Catalogue details

Licence: In copyright

Credit: British blood-sucking flies / by F.W. Edwards, H. Oldroyd, and J. Smart. Source: Wellcome Collection.

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    In a generalised insect the mouth parts consist ol the lahium, a pair of maxillae, a pair of mandibles and the labruin. I he hypopharvnx is a tongue- like projection on the floor of the mouth on which is situated the opening of the salivary duct. In blood-sucking Diptera the hypopharvnx and the labruin are produced into awl-like structures which together form a tube up which the blood is sucked when they are inserted into llu1 skin of the victim. Coagulation of the blood and consequent blocking of the mouth parts is apparently prevented bv the salivary secretion which is poured into the wound. In the Xematoccra and the Braehycera the wound is cut by the mandibles and the maxillae, both of which are usually furnished with serrate cutting edges, and are inserted into the wound together with the labium and hypo- pharynx. The labium is soft and fleshy and is not inserted into the wound ; its function is to protect the cutting and sucking parts and to guide and support them when they are brought into use. The size and delicacy of the various parts varies ; in the Culicidae they are very elongate and extremely delicate while in the I abanidae they are short and quite stout. In the males the mouth- parts are constructed on the same lines but the degree to which they are developed as cutting appliances is much less than in the females, as would be expected from their non blood-sucking habits. In the Cyclorrhapha the mandibles and the maxillae are completely atro- phied, no trace of them can be seen, and the actual cutting of the wound is performed by the labium. In the blood-sucking Cyclorrhapha the labium is in the form of a horny stylet and it is actually inserted into the wound. The tip of the labium is rasp like and it is grooved above to accommodate the elongated labruin and hypopharvnx. The males of the cyclorrhaphous blood-sucking species take blood as well as the females. It is possible amongst them to trace the development of the blood-sucking habit and the correlated evolution of piercing mouth parts. Starting with species having normal mouth parts, which are attracted to wounds and suck up the blood oozing from them, the chain leads through species (not found in the British Isles , which are able to scratch the skin with their labium till the blood oozes and can be sucked up, to the species (mentioned in this book : which actually bite and penetrate the skin in their quest for blood. Blood-sucking Hies take more than one blood meal in the course of their lives, and are thus liable to transmit disease from one person or animal to another. The subject is a complex one that cannot be entered into here but it gives these insects a tremendous importance in the Tropics and some other parts of the globe. Certain diseases, such as malaria and sleeping sickness, cannot be transmitted naturally in any other way than through the agency of a blood-sucking fly, a mosquito in the case of malaria and the Tse-tse fly in the case of sleeping sickness. So far as is known they are of relatively little importance in this respect in the British Isles but notes on their status will be found in the sections of this book dealing with the separate families. In the introduction to the first edition of this work it was stated that of the eight (or nine groups of Diptera, of which some members have developed the blood-sucking habit, seven occur in Britain, and that of the total of about 2,700