Anatomy and histology of the alimentary tract of the female of the biting midge Culicoides nubeculosus Meigen (Diptera: Heleidae=Ceratopogonidae).

The adult blood-sucking females of a number of species of Culicoides are pests in many parts of the world. The irritation and annoyance caused by their attacks on man and his animals are often so great that they constitute a serious problem. The chief significance, however, of Culicoides spp. is that they may act as vectors of filarial and virus diseases to man and his animals (see Hill, 1947). C. nubeculosus, in particular, was found by Steward (1933) to be the vector of Onchocerca cervicalis, which infests the cervical hgament in horses and is the principal cause of nuchal disease (fistulous withers and poll-evil) in England. It is also incriminated by Moignoux (1952) asthe vector of 0. reticulata, which infests the suspensory hgament of the pastern joint of horses in the south of France. In view of the economic importance of Culicoides spp. as pests and as vectors of disease, much attention is being paid to their study in many parts of the world. Hitherto, however, no attention has been paid to the study of the alimentary tract, especially that of the female, in any species. To my knowledge, the references on this subject are confined to a figure of the alimentary tract of C kiefferi (plate XXII), an elementary account of the Malpighian tubules given by Patton & Cragg (1913), and some brief class-notes and figures of the alimentary tract and the salivary glands (pp. 135, 140, 149) of C. varius (?) (probably C. obsoletus Mg., syn. Ceratopogon varius Winnertz, 1852, Linn. Ent. 6, 35; see Edwards, 1939, p. 143) given by Patton & Evans (1929). Since the alimentary tract constitutes the environment of the ingested parasites, it has therefore a special importance and for this reason it has been studied in many blood-sucking flies. The present work attempts to extend our knowledge to the alimentary tract of Culicoides and to relate this to the previous studies on other biting flies. C. nubeculosus was chosen for this study because it is the only species which, hitherto, has been maintained as a laboratory culture, so that adults can be obtained at intervals throughout the year. As males are of no importance as vectors of diseases, the study was confined to the females.