A key is given to the larval instars, of which there may be nine or more, of Inopus rubriceps (Macq.) and I. flavus (James); the key is based on setal characters and development of the cranial lobes. Characters allowing recognition and sexing of the pupae are also described.

During the past few months the writer conducted observations to determine, first, if Aëdes aegypti preferred places of oviposition within habitations or those located outside with natural shelter near by, and, second, the distance from human habitations at which this species may breed. These investigations were carried out in, or near, the compound of the West African Yellow Fever Commission at Yaba, near Lagos, Nigeria.

Multilocus electrophoresis was used to study the genetic variation of field samples of Culex quinquefasciatus Say from Mali, Burkina Faso, Nigeria and Mozambique, and a laboratory strain from Senegal. Phallosome morphology (the DV/D ratio) was used for the taxonomic identification of the males. The proportion of individuals with a highly active esterase pattern, indicating resistance to organophosphorus insecticides, ranged from 0 to 0·75 in the field samples and was 1·00 in the Senegal strain. The following 17 loci were genetically analysed: α-Gpdh, Mdh-1, Mdh-2, Me-1, Me-2, Idh-1, Idh-2, 6Pgdh, G3pdh, Got-1, Got-2, Hk-1, Adk, Pgm, Aid, Tpi and Gpi. Comparisons made with published data for C. pipiens L. from the Old World and C. quinquefasciatus from the USA revealed similar levels of genetic variability in C. quinquefasciatus from Africa (H e = 0·06, P = 0·44, A = 1·47) and the USA, but considerably higher variability in C. pipiens (H e = 0·14, P = 0·52, A = 1·64). C. quinquefasciatus populations appeared genetically much more homogeneous than those of C. pipiens (average Nei's D = 0·004 within the former taxon, about ten times more within the latter) and the genetic divergence between African and USA samples of C. quinquefasciatus was very low (D = 0·003). Comparison between C. quinquefasciatus from Africa and C. pipiens showed that the former is genetically more related to C. pipiens s.s. from Italy (D = 0·145) than to C. pipiens form molestus Forskål from Italy (0·186) or Egypt (0·165). The average genetic distance found between C. quinquefasciatus and C. pipiens was 0·17, a value observed for some pairs of mosquito sibling species. Allele frequencies at some loci (Me-2 and Got-2) appeared to be remarkably differentiated between C. quinquefasciatus and C. pipiens, with fixed alternative allozymes at the Me-2 locus: 106 in C. quinquefasciatus, 100 and 108 in C. pipiens. These findings provide a basis for the investigation of gene flow between contiguous or overlapping populations of these two taxa in order to ascertain their relative taxonomic status.

Spatial and temporal dynamics of rapidly growing populations of tsetse flies at Nguruman, southwest Kenya during 1993–1995, were investigated, following six years of intensive population suppression with traps over a c. 100 km2area. The two tsetse species present were randomly distributed in the short rainy season, but were aggregated in the dry and long rainy seasons. Maximum temperature was the dominant weather factor associated with the degree of aggregation. Trends in catches at 20 fixed sites along an 18 km north–south axis were weakly correlated between locations, possibly representing population sub-structuring. In particular, trends in population change were poorly correlated between the area with a long history of trapping suppression in the south and the area with a more recent history of suppression in the north. On a micro-geographic scale, correlations among paired trap catches were clearly related to geographical proximity for Glossina pallidipes Austen (r2 = 0.55); whereas this relationship was quite weak for Glossina longipennis Corti (r2 = 0.12). Positive correlations among trap catches were significant for sites separated by less than c. 3.8 km (G. pallidipes) or 4.8 km (G. longipennis). These results suggest the existence of different population substructures in the two species on a relatively small geographic scale.

A previous paper in this Bulletin dealt with the economic entomology of the British Solomon Islands Protectorate up to the year 1932. The present article concerns research conducted after that date with special reference to the biological control of two insect pests.

The tick, Ornithodoros moubata, was named by Murray in 1877 as Argas moubata; his specimens came from Angola (Portuguese West Africa), where twenty years earlier, Livingstone had noticed that such ticks were common in native huts; but Murray's description was “quite useless” (Nuttall & others, 1908) and it was Pocock (1900) who first published a recognizable description of the species and distinguished between 0. moubata and 0. savignyi (Audouin).

The water loss and mortality of Calandra granaria (L.) and C. oryzae (L.) have been studied at low pressures in controlled humidities. The mortality of both species is closely associated with the loss of water under these conditions, a loss which is prevented by a high humidity in the surrounding air. C. oryzae is consistently more susceptible than C. granaria. Substantially linear relations were observed between water loss and decreasing relative humidity (range 0–85%), increasing period of exposure (range 4–16 hr.), and decreasing pressure (range 2–8 cm. mercury). At lower pressures (3–4 mm. mercury), the Water loss and mortality of both species were greatly reduced, suggesting that some physical change had occurred in the insects. A covariance analysis of the mortality response, using the loss of water as a concomitant variate, showed that there was no significant part of the mortality that was not accounted for by the water loss from the insects.

Microsatellite markers were used to investigate the genetic structure among invasive L. decolor populations from Australia and a single international population from Kansas, USA to determine patterns of dispersal. Six variable microsatellites displayed an average of 2.5–4.2 alleles per locus per population. Observed (HO) heterozygosity ranged from 0.12–0.65 per locus within populations; but, in 13 of 36 tests, HO was less than expected. Despite low levels of allelic diversity, genetic structure estimated as θ was significant for all pairwise comparisons between populations (θ=0.05–0.23). Due to suspected null alleles at four loci, ENA (excluding null alleles) corrected FST estimates were calculated overall and for pairwise population comparisons. The ENA-corrected FST values (0.02–0.10) revealed significant overall genetic structure, but none of the pairwise values were significantly different from zero. A Mantel test of isolation by distance indicated no relationship between genetic structure and geographic distance among all populations (r2=0.12, P=0.18) and for Australian populations only (r2=0.19, P=0.44), suggesting that IBD does not describe the pattern of gene flow among populations. This study supports a hypothesis of long distance dispersal by L. decolor at moderate to potentially high levels.

A study on populations of Glossina morsitans morsitans Westwood on Antelope Island, Lake Kariba, Zimbabwe provided Jolly-Seber (J-S) mark–recapture estimates of adult survival and Moran curve estimates of the overall survival of all developmental stages. For females, Moran survival estimates derived using ox fly-round catches showed similar trends to, but were more variable than, those calculated from J-S population estimates. Regression of one set on the other removed only 26% of the variance. Undue emphasis should not be placed on small changes in Moran survival estimates based on sequences of catches. Catch data cannot provide Moran estimates of male survival probabilities and no comparison is thus possible with estimates from the J-S data. The J-S and the Moran approaches were combined to estimate survival probabilities of the immature stages of male and female tsetse. The overall survival per three-week period averaged 45% for males and 59% for females, comprising mature adult survivals of 27 and 46%, and pooled survivals of immature stages of 59 and 77%, respectively. The high survival of immature flies is due to the sheltered, inactive nature of pupal life. Adult and overall survival probabilities were highly correlated in males (r2 = 0.61) but less so in females (r2 = 0.24) where capture rates were lower and variance in the results greater. Immature and overall survival was more highly correlated for both sexes, with r2 = 0.77 and 0.53 for males and females respectively. When a fixed pupal mortality of 1% per day was assumed, estimates of the survival of young adult males suggested that these were even lower than the survival of mature flies at the harshest times of the year, but were not markedly different when overall survival was high. Assuming equal mortality in all adults enabled the estimation of pupal survival. These had high variances but there was no evidence of any difference between the survival probabilities of male and female pupae.

Field tests were conducted on Soutra Hill (1,100 ft. above M.S.L.) in the winters of 1953–4 and 1954–5 to find a suitable larvicide for controlling Culicoides impunctatus Goetgh. In one trial, four formulations (wettable powder, water-miscible concentrate, oil solution and dust) of DDT and γ BHC were applied to plots (10 × 10 yd.) at dosages of 3, 12, 50 and 200 mg. p.p′DDT or γ BHC/sq. ft., except for the γ BHC dust which was applied at 3, 6, 12 and 25 mg. γ BHC/sq. ft. In a second trial, the larvicidal properties of aldrin, dieldrin and malathion wettable powders, chlordane water-miscible concentrate and malathion emulsi-fiable liquid were investigated at three or four of the following dosages —3, 6, 12. 25 and 50 mg./sq. ft. The conclusions to be drawn from these trials were:—

1. DDT was superior to γ BHC at all dosages and in all formulations both in immediate and residual effects.

2. For immediate larval control, DDT and γ BHC wettable powders and DDT water-miscible concentrate were effective but γ BHC water-miscible concentrate was relatively ineffective.

3. Although all the DDT preparations were effective as residual larvicides, the wettable powder was the most successful.

4. For immediate larval control a dosage of 200 mg. p, p′DDT or γ BHC is required. The effect produced by 50 mg./sq. ft. is variable.

5. For residual larvicidal action a dosage of 50 mg./sq. ft. is required although 12 mg./sq. ft. may sometimes be effective.

6. Both preparations of malathion reduced the initial larval density by just over half but they had no residual effect.

7. Chlordane and aldrin achieved an immediate larval reduction of one third but whereas chlordane had a greater residual effect, aldrin was ineffective.

8. Dieldrin had very little immediate (20 per cent. control) but considerable residual effect (72 per cent. control).

9. Wettable powders are the most successful larvicidal preparations.

10. DDT and γ BHC wettable powders at 50 mg. p, p′DDT or γ BHC/sq. ft. are superior to chlordane at the same dosage and slightly better than dieldrin at 25 mg./sq. ft.

Experiments on the effect of changes in relative humidity on the toxicity of DDT- and DNC-films to adults of Tribolium castaneum and larvae of Plutella maculipennis are described. With T. castaneum adults the toxicity of both DDT and DNC films is increased at higher relative humidities, but with larvae of P. maculipennis the toxicity of DDT films decreases while that of DNC films increases at higher humidities. Like these experiments the perusal of the literature does not help in deducing any general principle. However, it is possible to collect instances showing that besides the insect and the insecticide, there may be various factors like the range of humidity tested, the strength of the insecticide used, the stage of the insect, etc., which can affect the result of humidity changes.

The sandflies of the two largest Italian foci of visceral leishmaniasis, Naples and Catania, were studied.

The following species were found : P. papatasii, P. perniciosus, P. sergenti, P. vesuvianus, sp. n., P. parroti var. italicus var. n.

P. papatasii and P. perniciosus are the commonest sandflies in the areas examined.

Out of 1,547 ♀♀ dissected none showed a natural infection with Leishmania.

P. papatasii was infected with Italian strains of L. infantum by feeding on cultures through membranes. The infection rate was low, but in contrast to Indian strains of L. donovani in the same sandfly, the infection once established did not die out.

(1) A. elutus females in Palestine show seasonal variations of fertility, but these do not appear to explain fully the distribution of adults throughout the year.

(2) Females of the overwintering generations show low fertility. This depends probably on conditions of larval life.

(3) The seasonal changes in the egg of A. elutus in Palestine are due to temperature variations. It is suggested that these changes are protective adaptations against cold in winter and excessive heat and irradiation in summer.

(4) The entering of the hibernation stage of A. elutus in Palestine cannot be considered as a pure consequence of the low temperature in autumn, since spring activity begins at a much lower temperature.

(5) During hibernation the females feed, but do not bring eggs to maturity ; the blood is used for fat accumulation.

(6) During the second half of the hibernation period the females lose their reserve materials.

(7) Full fat females starved in the laboratory lose their fat-body reserves, and simultaneously their ovaries develop to stage 2. Under the prevailing temperature the process requires about 3 weeks.

(8) A slow development of the ovary is going on during hibernation, but never proceeds beyond the second stage. The ovaries in a large percentage of females reach this stage at all times when reactivity occurs at the end of the hibernation period.

The new material received from the Imperial Bureau of Entomology through the kindness of the Director, Dr. G. A. K. Marshall, enables me to prepare this third paper on the Ethiopian fruit-flies. It is a proof of the great richness of the African Trypaneid fauna that of over 41 species received only 10 were referable to previously described species, and that no less than 8 new genera have been erected, most of them for very strikingly characterised forms.

At the present moment our knowledge of the Dipterous fauna, including the Tabanidae, of Palestine is little better than complete ignorance, consisting as it does solely of a few isolated records of species—chiefly mosquitos. The following paper, which it is intended shall be succeeded by others dealing with other families of Diptera, based upon material collected by the author in Palestine during the recent campaign against the Turks, is a modest attempt to lift one small corner of the veil of obscurity.

Observations made in Uganda on eight individuals of the mosquito Toxorhynchites brevipalpis conradti Grünb. reared in captivity from egg to adult are recorded. Larvae of this species are predatory and coexist in tree holes with those of mosquitos of medical importance.

The identification of larvae and pupae is discussed, and information provided on the following subjects: the amount of food (living larvae of Aedcs acgypti (L.)) needed for larvae to complete development; the feeding and killing behaviour of fourth-instar larvae; duration of the pupal stage; and the rate of autogenous ovarian development in the unfed female adult.

The compulsive killing behaviour shown by a fourth-instar larva about two days before it pupates could be expected to cause the death of all the other mosquito larvae in a tree hole of average size. This species is unusual among mosquitos in that pupae of females developed more rapidly than those of males.

From the above it will be seen that in the writers' opinion, based it must be admitted on but a single year's observations, the three species of Dysdercus (D. fasciatus, D. nigrofasciatus and D. superstitiosus) occurring in the northern rain-cotton belt of the Sudan are essentially associates of the tebeldi and are not as yet other than accidental pests of cotton. By this is meant that there is no definite migration from the tebeldi to cotton, nor are wandering adults greatly attracted by cotton. The dispersal of a proportion of the adults composing a colony on a tebeldi is the natural effort on the part of the species to establish itself on other tebeldis. Emigrants from a colony that in the course of their wanderings chance on cotton may remain to breed. It is possible that when cotton has been grown in the district on a large scale for some years, the bugs, unless they are kept in check, may develop the habit of migrating definitely from the tebeldis to the cotton and, later in the season, from the cotton back to the tebeldis.

The most promising line of attack appears to be that of destroying, so far as possible, the colonies on the tebeldis during the active breeding season.

The writers' thanks are due in particular to Mr. G. F. March, Inspector of Agriculture, who in a variety of ways has rendered them the greatest assistance in their work.

Rainfall records for 23 years at 21 selected stations in Kenya were summarized and compared with the numbers of outbreaks of armyworm Spodoptera exempta (Walker) reported in the following season. The numbers of outbreaks were found to be negatively correlated with the rainfall of the 6–8 months preceding the start of the season. Stations in south-eastern Kenya, including the coastal belt which harbours the most extensive off-season source populations of S. exempta, were identified as key stations for forecasting whether to anticipate local or countrywide armyworm outbreaks next season. A scheme is suggested that would enable a provisional forecast to be made as soon as the long rains (April–May) rainfall records were available, and confirmed or revised subsequently in the light of the June–October rainfall at stations in south-eastern Kenya.

A study was made of the seasonal variation in population density of larvae of Boophilus microplus (Can.) in four locations in Jamaican pastures where the mean annual precipitation ranged from 59 to 222 cm. Variations in population density were related to rainfall. Generally, four months of heavy rains in August to November preceded significant increases in B. microplus populations in December to February. This was followed by a reduction then another slight increase, resulting in a bimodal pattern of activity. Although populations fell to very low levels by the end of the dry season, only in one focus were they depleted to undetectable levels.