Honeybees cannot synthesize arachidonic acid (ARA) themselves, only obtain it from food. Most pollen is deficient or contains a small amount of ARA. The necessity of supplementary ARA in bees’ diet has not been studied. The objective of this study was to investigate the effects of dietary ARA levels on the growth and immunity of Apis mellifera ligustica. A total of 25 honeybee colonies were randomly assigned to five dietary groups which were fed basic diets supplemented with 0, 2, 4, 6, and 8% of ARA. The diet with 4% ARA improved the body weight of newly emerged worker bees compared with the control group. Supplement of ARA in honeybee diets changed the fatty acid composition of honeybee body. SFA and MUFA contents of bees’ body declined, and PUFA content rised in the ARA group. Compared with the control group, the supplement of ARA in honeybee diets increased the contents of ARA, C22:6n-3 (DHA) and C18:3n-6 in bees’ body significantly, but decreased the contents of C16:1 and C18:3n-3. The diet supplied with 4% ARA reduced the mortality rate of honeybee infected with Escherichia coli. The activity of immune enzymes (phenoloxidase, antitrypsin, and lysozyme) and the mRNA expression levels of immune genes (defensin-2, toll, myd88, and dorsal) were improved by ARA diets to varying degrees depending on the ARA levels, especially 4% ARA. These results suggested that dietary ARA could improve the growth, survival, and immune functions of honeybees. Supplement of ARA in bees’ diet would be valuable for the fitness of honeybees.

Twenty-five species of Simuliids are listed with indications of their relative abundance, importance as pests of man, seasonal appearance, temperature requirements, and larval habitats in Labrador. Seven of these are undescribed species. The most important species are Simulium venustum Say and Prosimulium hirtipes (Fries).

A circular area of 200 square miles around Goose Bay airport was surveyed for important breeding sites. Of 163 streams and rivers investigated, 77 were suitable as larval habitats, and larvae were virtually eliminated from them in June, 1950, by applications of a 10 per cent, solution of DDT in fuel oil at the rate of 1–5 p.p.m.- minutes from a helicopter, conventional aircraft, or boats, or by hand application from the ground. Methods of application are discussed.

The repopulation of the area by black flies was studied, and deductions are made concerning the flight habits of the most important species. On the basis of averages throughout the season, a great reduction in numbers of black flies at the centre of the area was obtained, and a worth-while reduction to a distance of between 4 and 6 miles from the centre. Even near the centre of the area, however, black flies were sometimes troublesome late in the season.

It is suggested that, where P. hirtipes is the important species, relief for at least one season could be secured by eliminating larvae within a radius of 2 miles; for S. venustum, 6 miles is suggested as a suitable radius. No adverse effects on useful animals were recorded.

1. All polysaccharides fed to Melanoplus have been utilised incompletely or not at all.

2. Rupture of the starch granule renders it partly utilisable.

3. Glucose, galactose and xylose are completely absorbed.

The biology of Bubas bison (L.) was studied in southern France. It was active from September to the end of May. Adult emergence lasted from September to January; 8 % of the female population was parous and laying eggs in September, and 100% were parous from February to the end of June. Females exhibited extraovariolar egg resorption, which may have been a response to adverse conditions. Eggs laid in October, November, February and March hatched synchronously in May. Adults resulting from eggs laid in March emerged in early September. The rate of oviposition varied from 0–03 egg/day in January to 0·5 in March. Females stopped laying eggs for three weeks in January. The structure of the nests formed from buried dung brood-masses was studied. Each brood-mass contained two eggs, one at each pole. About 12 brood-masses were formed under each dung pad in October 1981. The mean length of each mass was 96 mm and the dry weight 10–5 g. The mean number of masses in a nest was 24, with a mean number of 4–9 nests under each dung pad. The dry weight of dung buried under a pad in October 1981 was 1239 g, 66–6%, of the mean dry weight of an experimental dung pad. B. bison has the potential for recycling large amounts of dung in climatic areas of Australia equivalent to southern France.

Two generalist parasitoids, Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) and Therophilus unimaculatus (Turner) (Hymenoptera: Braconidae) attack early instars of tortricid moths, including the light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). The two parasitoids co-exist in natural habitats, while D. tasmanica is dominant in vineyards, whereas T. unimaculatus occurs mainly in adjacent native vegetation. This difference suggests possible competition between the two species, mediated by habitat. Here, we report on the extent of interspecific differences in host discrimination and the outcome of interspecific competition between the two parasitoids. The parasitoids did not show different behavioural responses to un-parasitized hosts or those that were parasitized by the other species. Larvae of D. tasmanica out-competed those of T. unimaculatus, irrespective of the order or interval between attacks by the two species. The host larvae that were attacked by two parasitoids died more frequently before a parasitoid completed its larval development than those that were attacked by a single parasitoid. Dissection of host larvae parasitized by both species indicated that first instars of D. tasmanica attacked and killed larval T. unimaculatus.

Female, adult. More or less circular or faintly pentagonal ; low convex ; pseudo-margin strongly rounded, giving the insect a markedly “crustliform” (Green) appearance ; margin very thin and shallow ; anterior stigmatic clefts well defined. Dorsum with a slightly subcentral depression, from which there arise strong radial striae extending to the pseudo-margin. Anal cleft fused. Anal lobes in the subcentral depression, so that they appear almost in the middle of the back. Colour of dorsum brownish black, with minute reddish-buff glandular spots. Venter coffee-brown. Detached scurfy particles of a somewhat glassy secretion within the pseudomargin, and six larger particles of similar material, each resting upon a minute tubercle, arranged in a parallelogram near the central depression. Derm cells closely packed together, very irregular in shape, many being markedly attenuated at one extremity; these are divided into more or less definite radial bands corresponding to the spaces between external striae; in the central area of the dorsum they are almost obscured by the dense chitin, so that only the minute central pores are traceable; in this same area are a number of larger and clearer pores varying considerably in size, the larger ones radiating from the anal lobes.

A description is given of the method used for the large-scale breeding of cotton stainers (Dysdercus spp.) at the Cotton Research Station in Uganda. The method entails the use of a standard cage unit, consisting of a shallow tin cylinder with detachable cloth top and bottom. The advantages of this type of unit are outlined, with particular reference to control of disease and to the other hazards of large-scale breeding.

It is important to understand how components of the agroecosystem interfere with the attack of a pest species and their seasonality in order to use these components in IPM programs. This study focused on the evaluation of the seasonality of natural control factors associated with the guava psyllid Triozoida limbata (Enderlein) in Brazil. Life-table data were collected from an experimental guava orchard during four periods that roughly represented four seasons. Natural mortality was monitored daily through the immature stages, and the relative importance of each natural mortality factor and its seasonality was determined. Significant statistical differences were observed in the mortality during the four periods (P < 0.05). Several factors contributed to the mortality of T. limbata, including rainfall, physiological disturbance, the parasitoid Psyllaephagus sp. (Hymenoptera: Encyrtidae) and specific predators: syrphids, predatory wasps and other generalist predators. Depending on the location of nymphs (exposed or inside galls), the relative importance of the different natural mortality factors changed. The principal component analysis (PCA) showed some trends in the relationship of natural control agents and weather conditions. For example, the occurrence of predatory wasps was positively correlated with temperature and occurrence of winds; the occurrence of syrphids and Psyllaephagus sp. were negatively correlated with temperature and winds; and the occurrence of other generalist predators were negatively correlated with the occurrence of rainfall and photoperiod. The results showed the importance of natural mortality factors for the management of T. limbata and their changes through the different seasons which should be considered when implementing IPM programs in guava orchards.

The human helminth parasite burdens on cyclorrhaphan flies was studied in an aboriginal settlement in Malaysia in 1987–88. Chrysomya megacephala (F.), which formed 79.5% of total fly population trapped in this settlement, had eggs of the roundworm Ascaris lumbricoides, the pinworm Trichuris trichiura and hookworm (Necator americanus and/or Ancylostoma duodenale) on the external body surface and gut lumen. There was a close correlation between monthly rainfall and the mean numbers of C. megacephala caught per two trap-hours. Eggs (but no larvae) of the parasites were found on flies when the monthly rainfall and the C. megacephala population were relatively high, in April-June 1987, October-November 1987 and March 1988. Human helminth eggs were also isolated from C. rufifacies (Macquart) and Hemipyrellia tagaliana (Bigot), being recorded from the latter in Malaysia for the first time.

A computer model of a tsetse population was developed to determine whether insecticide resistance could evolve as a result of current tsetse control programmes. Chemical analyses were also carried out which showed that Glossina morsitans morsitans Westw. can metabolise DDT to DDE, indicating a potential for insecticide resistance in this species. The model showed that a completely isolated tsetse population stands little chance of surviving attacks with insecticides repeated at short intervals. However, when sufficient time is allowed between applications, such a population may survive and evolution of resistance take place. Given a small amount of immigration, the evolution of resistance is retarded, but population extinction is prevented. The degree of resistance developed by a population also depends on the dominance relationship of a resistant gene with its wild-type allele and on the reproductive fitness of the mutant. It is suggested that control strategies are adopted which would minimise the risk of insecticide resistance becoming a problem in tsetse and that susceptibility studies are carried out both before spraying operations and on any residual population post-spraying.

Cryptolestes capensis (Waltl) has been reared successfully upon wheatfeed at constant temperatures of 15 to 32·5°C., at intervals of 2·5°C., and 90 per cent. R.H., and at 30°C. and 10 to 70 per cent. R.H. Newly formed adult males were found to weigh more than females bred under the same conditions. Oviposition was investigated at 90 per cent. R.H. and 17·5, 20, 30 and 32·5°C.; the highest rate was at 30°C. It was concluded that 30°C., 90 per cent. R.H. were the optimal conditions of those observed. Comparison with C. turcicus (Grouv.) which occurs in the same habitat as C. capensis, shows that the temperature limits of the former are higher, but that at those temperatures at which both species can breed, there is little, if any, difference between the total duration of the immature stages. At the observed optimum for the two species, C. capensis has a higher innate capacity for increase than C. turcicus. These observations do not account for the rarity of C. capensis in comparison with C. turcicus, and it is postulated that C. capensis is, like C. ferrugineus (Steph.), more susceptible to the harmful effects of high larval density than is C. turcicus.

Development and reproductive success of the solitary egg parasitoid Uscana lariophaga Steffan were examined after development in eggs of the bruchid storage pest Callosobruchus maculatus Fabricius reared at either low or high densities on cowpea seeds and laid at day 1 and 4 of maternal life. Both bruchid larval competition and maternal age negatively affected egg size, but the latter more than the former. Uscana lariophaga reared in small hosts developed slower, were smaller and produced fewer eggs compared to parasitoids reared in large hosts. Fecundity of the parasitoid was heavily influenced by host egg size. This was reflected in the values for the intrinsic rate of increase of U. lariophaga, which differed for wasps that developed in host eggs laid by bruchid females of different age. Wasps allocated marginally more female offspring to larger hosts.

Ten insecticides were assayed for toxicity against an unselected and a resistant strain of Myzus persicae (Sulz.). Of the six topically applied insecticides parathion was the most effective, followed by diazoxon, diazinon, aldrin, dichlorvos and p, p′DDT in that order, while the resistance levels were, in descending order, parathion, dichlorvos, diazinon, diazoxon, p, p′DDT and aldrin. Of the four systemic insecticides, pirimicarb was most toxic, followed by dimethoate, phorate and demeton in that order, while resistance ratios were in descending order dimethoate, phorate, demeton and pirimicarb. The organophosphorus resistance spectrum for M. persicae indicated that more than one resistance mechanism is involved, and that resistance acts against diethoxy and dimethoxy compounds.

The robber fly Mallophora ruficauda is one of the principal apicultural pests in the Pampas region of Argentina. As adults, the flies prey on honey bees and other insects; while, as larvae, they parasitize scarab beetle larvae. Females of M. ruficauda lay eggs away from the host in tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig in search of their hosts. It is known that second instar larvae of M. ruficauda exhibit active host searching behaviour towards its preferred host, third instar larva of Cyclocephala signaticollis, using host-related chemical cues. Furthermore, previous works show that these chemical cues are produced in the posterior body half of hosts. However, the precise anatomical origin of these cues and whether they mediate any behaviour of C. signaticollis larvae remains yet unknown. In order to determine the precise origin of the chemical cue, we carried out olfactometer assays with different stimuli of extracts of the posterior C. signaticollis body half. Additionally, we tested whether C. signaticollis is attracted to any of the same extracts as in the previous experiments. We found that both second instar of M. ruficauda and third instar of C. signaticollis are attracted to extracts of the fermentation chamber (proctodeum). This is the first report of attraction of conspecific larvae in scarab beetles. We discuss a possible case of system communication exploitation in an immature parasitoid-host system.

In 1964–65, breeding sites of the tsetse fly G. tachinoides Westw. near Nsukka in south-eastern Nigeria were found in peri-domestic situations (particularly beneath stacked coco-yam tubers and at the base of fences of pig enclosures) and in adjacent farmland (particularly beneath banana and coco-yam plants, under Lantana camara, at the base of farmland fences and around derelict farm buildings). Between them, these sites provide moisture conditions suitable for year-round breeding of G. tachinoides and are not exposed to unsuitably high temperatures (>90°F) for long periods. The night-time resting sites of G. tachinoides in three villages five miles east of Nsukka were sought between May and November 1966 using ordinary torchlight. The most popular resting-sites were dried fronds of oil and coconut palms used for fencing pig enclosures, but a few flies also rested on man-made objects in the villages and on vegetation nearby. Most flies were resting less than two feet above ground level. Day-time observations confirmed the night-time findings. G. tachinoides could probably be controlled, if not eradicated, in the Nsukka area by two applications, a fortnight apart, of DDT emulsion concentrate to pig enclosure fences and pig styes up to a height of 2–3 ft during March–May when the fly population is most concentrated around confined pigs.

Laboratory and field cage trials were made with male Glossina morsitans orientalis Vanderplank treated with tepa or gamma irradiation to assess the ability of the sterile males to compete with untreated males for normal females when the ratios of treated males to untreated males to untreated females ranged from 4:1:5 to 5:2:5. Irradiation of the pupal and adult stages with 8000 and 15000 rad or 8000 and 12000 rad, respectively, reduced reproduction by 87–100% (mean, 95%). Contact for 60 min on a glass surface coated with 10 mg tepa/ft2 or exposure to 0·25 ml of 5% tepa in a wind tunnel usually produced complete sterility (mean, 99%) in 0- or 2-day-old male flies. Trials in the laboratory and in a small field cage (288 ft2) with chemosterilised flies generally reduced reproduction to near the expected values. Similar results were obtained with male flies emerging from irradiated puparia, but males treated as adults produced somewhat smaller reductions than expected. Unreplicated competitive trials with chemosterilised and irradiated males in a large field cage (8100 ft2) produced considerably smaller reductions in reproduction than expected, suggesting that treated males released in nature might not compete for normal females as readily as untreated males.

20-Hydroxyecdysone (20E) is a key hormone which regulates growth, development and reproduction in insects. Although cytochrome P450 enzymes (P450s) participating in the ecdysteroid biosynthesis of 20E have been characterized in a few model insects, no work has been published on the molecular entity of their orthologs in the cotton bollworm Helicoverpa armigera, a major pest insect in agriculture worldwide. In this study, four cytochrome P450 homologs, namely HarmCYP302A1, HarmCYP306A1, HarmCYP314A1 and HarmCYP315A1 from H. armigera, were identified and evolutional conservation of these Halloween genes were revealed among lepidopteran. Expression analyses showed that HarmCYP302A1 and HarmCYP315A1 were predominantly expressed in larval prothoracic glands, whereas this predominance was not always observed for HarmCYP306A1 and CYP314A1. The expression patterns of Halloween genes indicate that the fat bodies may play an important role in the conversion of ecdysone into 20E in larval–larval molt and in larval–pupal metamorphosis, and raise the possibility that HarmCYP315A1 plays a role in tissue-specific regulation in the steroid biosynthesis in H. armigera. These findings represent the first identification and expression characterization of four steriodogenic P450 genes and provide the groundwork for future functional and evolutionary study of steroid biosynthesis in this agriculturally important pest.

1. The paper describes work carried out to find the causes of certain discrepancies in the results of longevity experiments on rat-fleas.

2. The following factors were found to reduce significantly the survival period of unfed adult fleas:—

Rearing larvae together rather than in separate tubes; Parent fleas over 11 days old; Using very fine rather than coarse sand as a matrix for larval food; Drying the blood for larval food by baking rather than in a vacuum over sulphuric acid at room temperature.

3. The following factors were found to have no significant effect upon adult longevity:—

Contamination of larval food by mice and their droppings;

Presence or absence of adult flea faeces in larval food.

4. The effect upon the weight of larvae and the duration of the larval period of some of the above-mentioned factors is described. The female larval period is shown to be shorter than that of the male under all conditions used.

5. It is confirmed that there is no significant difference between the longevity of male and female adults which have fed once or not at all, and that females which have fed frequently before starvation live longer than males.

6. Well developed, unfed, laboratory-bred adult fleas live longer than those which have fed once before starvation, and the latter live longer than those which have fed several times.

7. There is some evidence that unfed wild-caught fleas live longer than wildcaught fleas which have fed, but this needs confirmation.

8. All the available information regarding factors affecting adult longevity is summarised in a table.

Mutualistic relationships between honeydew-producing insects and ants have been widely recognized for several decades. Iridomyrmex rufoniger (Lowne) is the commonest ant species associated with black scale, Saissetia oleae (Olivier), in the citrus orchards of the mid latitudes of coastal New South Wales. Citrus trees with high densities of both red and black scale and high ant activity were identified and the results of excluding ants from half of those trees (using a polybutene band on each trunk) were compared with the results of not excluding ants from the other half. Trees with a low incidence of black scale and ants were also studied. Exclusion of ants from trees was soon followed by collapse of black scale populations because most individuals were asphyxiated by their own honeydew. Also, parasitism of the red scale by Encarsia perniciosi (Tower) and Encarsia citrina Craw was significantly higher than in the control trees over the following year, as was the predation rate on red scale due to three coccinellid predators, Halmus chalybeus (Boisduval), Rhyzobius hirtellus Crotch and Rhyzobius lophanthae (Blaisdell). In contrast, another coccinellid, Orcus australasiae (Boisduval), and a noctuid moth larva, Mataeomera dubia Butler, were seen in low numbers on banded (ant exclusion) trees, probably because of the low availability of their black scale prey, but were significantly higher on control trees apparently because of their invulnerability to ants.

During the six-month period from December 1925 to June 1926, some observations were carried out on the mosquito breeding that occurred in a number of “ test ” water-containers placed in various locations in the compound of the headquarters of the West Africa Yellow Fever Commission at Yaba, near Lagos, Nigeria. The main purpose of these observations was an endeavour to obtain supplemental information on the bionomics of the yellow fever mosquito, Aëdes (Stegomyia) aegypti, Linn., in West Africa.