Blood-sucking Diptera Research Articles

The ovarian cycle and egg stage in Leptoconops (Holoconops) becquaerti (Kieff.) (Diptera, Ceratopogonidae).

Leptoconops becquaerti (Kieff.) is one of the most troublesome species of biting midge in Jamaica. The gonotrophic cycle in this insect was studied and is described. In this species a single blood-meal is sufficient for the development of the ovaries and the maturation of eggs.The stages in follicle development and digestion of the blood-meal adopted for other blood-sucking Diptera have been applied to L. becquaerti with slight modifications. A high degree of gonotrophic harmony is present in this insect.Fully fed females were kept at five temperatures, 68, 77, 85, 91 and 98°F., to determine the time taken for the ovarian follicles to reach Stage V of development (egg mature, chorion present). The times were approximately 98, 64, 36, 30 and 27 hours, respectively.It was demonstrated that the number of ovarioles in L. becquaerti was proportional to the size of the individual (as measured by wing length). The average number of ovarioles in an insect of wing length 0.83 mm. (the mean wing length of the population sampled) was about 103.The number of eggs matured was also proportional to wing length, and was also dependent upon the temperature at which the flies were kept. Thus at the standard wing length of 0·83 mm., the average numbers of eggs matured at the five chosen temperatures (68 to 98°F.) were 78, 85, 65, 61 and 60, respectively. Females that had matured eggs were induced to oviposit by the decapitation technique.Females provided with a source of carbohydrate (honey) during egg maturation produced slightly more eggs on the average than those fed on blood alone. The comparable figures at 91°F. in the standard individual were 65 and 61, respectively. The probable rôle of supplementary carbohydrate feeding in nature is discussed.At the five experimental temperatures the greatest number of eggs hatched on days 11, 7, 5, 4 and 4, respectively, after laying. Egg-batches used in these experiments were deposited by decapitated females, and may therefore have been laid somewhat before the usual time in nature. The percentage fertility varied between individual batches at all temperatures, but the over-all fertility was consistently high (70–75%) at the lower four temperatures, and very low (4%) at 98°F. This difference almost certainly resulted from high temperature in the latter instance. Fertility in egg-batches deposited naturally (without decapitation) was of the same order as that in batches deposited by headless females.

Determination of physiological age for female Glossina morsitans.

RECENTLY, considerable attention has been paid to a method of determining the physiological age of female insects of economic importance by the appearance of the ovarioles after ovulation. This method, which was originally worked out by Soviet entomologists1,2 for Anopheles, and has since been extended to other blood-sucking Diptera, depends upon the recognition of the number of follicular relics (‘corpora lutea’) appearing as dilatations of the follicular tubes. Each dilatation represents the relic of a single egg follicle and is evidence of a gonotrophic cycle. If the duration of the cycle is known it is possible to calculate the calendar age of the female, a factor of great practical application in determining the epidemiological importance of populations of insect vectors or the degree of success of control programmes. In the laboratory, Bertram and Samarawickrema3 recognized Mansonioides uniformis which had completed five gonotrophic cycles by the presence of five dilatations in the follicular tubes. A study of the ovarioles of Glossina morsitans after ovulation has been made, and it is suggested that a similar method of determining the physiological age of female tsetse flies should be possible.

Influence of Black Fly Control on the Incidence of Leucocytozoon Disease in South Carolina Turkeys2

Experiments were conducted in Jasper County, S. C., to determine if the control of black flies ( Simulium ), vectors of Leucocytozoon smithi (Lavern & Lucet), would reduce or eradicate this disease in turkeys. Plots of approximately 11 and 4 square miles, each containing a turkey farm, were treated by aircraft with 5% DDT-oil solution at the rate of 0.033 pound of insecticide per acre to destroy black flies breeding in the streams. In the large plot good control of larvae and pupae was obtained for 4 weeks, and dry weather practically eliminated breeding during the following 8 weeks. Observations of turkey poults placed on pasture 4 weeks after treatment failed to reveal black flies, but Leucocytozoon infections were evident after 2 weeks’ exposure. Other blood-sucking Diptera collected from the turkeys included Culicoides spp., Aedes spp., Diachlorus ferrugatus (F.), and Chrysops univittata Macq. Good control of larvae was also obtained for 4 weeks in the small plot, and dry weather kept breeding at a low level thereafter. However, pupae of S. slossonae D. & S. and congareenarum (D. & S.) were collected nearly every week of the study, and a few adults may have been available to attack the turkeys. Leucocytozoonosis was evident after the turkeys were exposed 2 weeks on the pasture.

Ked-Flies

THE ked-flies are blood-sucking Diptera, ectoparasitic on certain of the ruminant artiodactyls. Since species occur on domesticated sheep and goats, they are of veterinary significance though not yet incriminated of acting as vectors of actual disease; occasionally they bite man. Information about these flies has been somewhat scattered, and a recent monograph1 of the group by Prof. J. Bequaert of Harvard is, accordingly, very welcome. Prof. Bequaert has already published many shorter papers on the Hippoboscidæ, of which the Melophaginæ or ked-flies are a sub-family; his monograph of the ked-flies is thus the outcome of prolonged study.

Structure of the Proboscis in Blood-sucking Diptera

WITH reference to Dr. B. Jobling's letter1, I wish to point out that, as already mentioned2, the hypothesis advanced by me concerning the feeding mechanism in blood-sucking diptera was of a tentative character, and that the object of my communication was not to generalise, but to report certain observations made by me on the feeding mechanism in one species of blood-sucking fly, namely, Stomoxys calcitrans. As a matter of fact, I have since carried out a large number of dissections upon specimens of several species of Culicines after feeding them on a strong solution of eosin sweetened with sugar, and while in a few instances no staining was found to have occurred in any part of the proboscis, in others it was the labrum-epipharynx that was found to have taken the stain along the whole of its length, indicating that the food-channel in insects of this class is probably formed by the apposition of the labrum-epipharynx and the hypopharynx.

A new Tsetse-fly of the Glossina palpalis Group occurring in Belgian Congo

In the autumn of 1928 Dr. J. Schwetz forwarded to the writer, from Stanleyville, a small collection of blood-sucking Diptera, the majority of which had been obtained by him in the region of the Lower Lomami River. The material sent included specimens of four species of Glossina, the determination of three of which (G. palpalis, Rob.-Desv., G. fusca, Walk., and G. tabaniformis, Westw.) presented no difficulty. The fourth species, however, which had evidently attracted the special attention of the sender, since specimens of it were received labelled “ ? G. pallicera,” proves to be new and is accordingly described below. Dr. Schwetz, who is already well known by reason of entomological investigations in Belgian Congo extending over a long series of years, is to be congratulated upon a discovery which brings the number of recognised species of Glossina up to twenty.

The Structure of the Head and Mouth Parts in Culicoides pulicaris, L. (Diptera Nematocera)

In view of the fact that many blood-sucking Diptera are carriers of pathogenic micro-organisms of animals and human beings, the study of the structure of their mouth-parts has attracted the attention not only of zoologists but of medical men as well.

A Contribution to Knowledge of the Blood-sucking Diptera of Palestine, other than Tabanidae

As in the case of the Tabanidae, which have already been described, the material upon which the following paper is based was collected by the author during the Palestine Campaign of 1917–18.

Advance in Economic Entomology

A NOTABLE feature of recent biological research is the attention paid by medical experts to the study of insects. Capt. F. W. Cragg, of the Indian Service, has lately published two Scientific Memoirs (Nos. 54 and 55) of the Medical and Sanitary Departments of the Government of India, which are of importance to students of the anatomy of Diptera. Both memoirs deal with blood-sucking species, No. 54 with Philaematomyia insignis, and No. 55 with Haematopota pluvialis. The excessively small number of males of the latter fly is believed by Capt. Cragg, after examination of the genitalia of the female insect, to be explained by heavy mortality as the result of pairing. We notice that the bibliography of this paper contains some remarkable misprints, of which “Verh. yool-bat. Gas. Wein” is worthy of record as a piece of unconscious humour! The last published part of the Bulletin of Entomological Research (vol. iii., part 4, December, 1912) contains valuable systematic papers on blood-sucking Diptera, by Mr. E. E. Austen and Prof. R. Newstead, and some very useful diagnoses of the larval stages of African mosquitoes, by Messrs. F. W. Edwards and A. T. Stanton.

XXVI.—Entomological notes from the London School of Tropical Medicine.—No. IV. Blood-sucking Diptera from Port Darwin, Australia

XXVI.—<i>Entomological notes from the London School of Tropical Medicine</i>.—No. IV. <i>Blood-sucking Diptera from Port Darwin, Australia</i>

Notes on the Blood-sucking Diptera met with in Eastern and South-Eastern Abyssinia

The highlands of Abyssinia are remarkably free from blood-sucking flies, if theCulicidæ,Stomoxys, andHippoboscidæare excepted.