1. An analysis of rice-field and canal waters was made over a period of 1 year.

2. The incidence of Anopheles tarsimaculatus in these fields and canals was noted.

3. The chemical factors estimated were pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates, phosphates and ammonia nitrogen.

4. No correlation was found between the incidence of A. tarsimaculatus and the following factors: pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates and phosphates.

5. In nature the female A. tarsimaculatus seemed to prefer waters with a low ammonia nitrogen content, larvae being rarely found in water with a content greater than 0·04 parts per 100,000. In the laboratory the larvae of A. tarsimaculatus lived several days in waters with an ammonia nitrogen content as high as 0·12 parts per 100,000. Therefore it was concluded that ammonia nitrogen had some bearing upon the prevalence of this Anopheles, affecting the oviposition of the female rather than the growth of the larvae.

The biocontrol potential of a microsporidian pathogen, Vairimorpha sp., obtained from field collected diamondback moth, Plutella xylostella Linnaeus, was assessed in a laboratory colony of this insect. The pathogenicity was quantified using a standard bioassay procedure by infecting second instar larvae per os with variable dose levels of the pathogen. Vairimorpha sp. caused 100% mortality even at a dosage of 1.5 x 103 spores per larva. The median lethal dose (LD50) was 2.2 x 104 spores per larva on day 5 post-inoculation. The time taken to achieve 90–100% mortality was dose dependent and varied from 5 days with 1.5 x 106 spores per larva to 11 days with 1.5 x 103 spores per larva. The pathogen reduced the food consumption of P. xylostella larvae by 75%, 93% and 95% at doses 1.5 x 104, 1.5 x 105 and 1.5 x 106 spores per larva, respectively. Histological observations showed that the pathogen preferentially infected adipose tissue cells but spread to almost all tissues. The pathogen was transmitted transovarially as well as horizontally and had a marked influence on progeny performance. It was concluded that Vairimorpha sp. has sufficient potential to be tested in the field as a biocontrol agent for P. xylostella.

The seasonal population trends of the immature stages of Aedes africanus (Theo.), an important vector of yellow fever virus and other arboviruses, were studied in Zika Forest, Uganda, for two years during 1974–75. Data were collected from natural breeding places in tree holes and from bamboo pots placed 80 cm above the ground. Developing larvae and pupae were present at all times of year, and there were monthly, seasonal and annual fluctuations in density. These fluctuations followed the seasonal distribution of rainfall and were more marked in the natural breeding places, which were subject to irregular fluctuations in water level, than in the bamboo pots, which were constantly supplied with water. Thus, in addition to the drought-resistant eggs whose erratic hatching by instalments could ensure the presence of A. africanus throughout the year, there are probably also present at any given time females that are capable of ovipositing. As a measure of the seasonal population changes, it was found that both the percentage of positive containers index and the mean number per container index were almost equally sensitive.

The use of multiple species in biological control programmes is controversial when interactions among them are not fully understood. We determined the response of the pupal parasitoid Coptera haywardi (Oglobin) to different availability of Anastrepha ludens (Loew) pupae previously parasitized or not by larval–pupal Diachasmimorpha longicaudata (Ashmead). The two types of pupae were exposed at different ages and proportions to different numbers of C. haywardi females for 48 h. The performance of C. haywardi adults emerging from parasitized and unparasitized pupae was measured. Coptera haywardi prefers to attack unparasitized A. ludens pupae rather than pupae parasitized by D. longicaudata. However, when the availability of unparasitized pupae was low or the number of foraging females was high, C. haywardi competed against early immature stages of the D. longicaudata, or hyperparasitized, feeding directly on the advanced-immature developmental stages of the early acting species. Adults of C. haywardi emerging as hyperparasitoids were no different in size, fecundity and longevity from those emerging as primary parasitoids. Our data suggest that simultaneous use of these species in augmentative biological control projects may be feasible but should be carefully planned in order to avoid any detrimental effect of its interaction.

Further observations and trials were conducted with insecticides against larvae of Culicoides impunctatus Goetgh. on Soutra Hill, Midlothian. The analysis of the data was complicated by a large natural reduction (76%) which occurred in the untreated plots. Nevertheless, it appears that the following dosages of insecticidal preparation were still active two years after application:—(a) 50 and 200 mg. p,p′DDT/sq. ft. applied as a dust, wettable powder or water-miscible concentrate (99% control), (b) 50 and 200 mg. γ BHC/sq. ft. as a wettable powder or 200 mg. γ BHC/sq. ft. as a water-miscible concentrate (95% control), (c) dieldrin at 25 mg./sq. ft., which gave 97 per cent, control and (d) chlordane at 50 mg./sq. ft., which gave 84 per cent. control.

The effect of spray volume on insecticidal effect was investigated by applying 25 mg. and 50 mg. p,p′DDT/sq. ft. in the following spray volumes:—5, 10, 15, 25, 50 and 80 gals./acre. The effect of 50 mg./sq. ft. at each volume was less marked than in the previous work, when only one concentration was used. Weather conditions in the present season were unusual, but there were indications that moderate spray volumes (15 and 25 gals./acre) give the best results at this dosage of insecticide. The combined results for 50 mg./sq. ft. at all volumes gave only 43 per cent, residual control, while those for the lower dosage showed no residual control.

The results are discussed with reference to the effect of rainfall on residual control. It is concluded that the volume of spray applied is unimportant provided the droplets of insecticide are closely and evenly distributed on the mossy vegetation that overlies the peat. Subsequent prolonged rain, of the order of 20 inches, is required to attain the most effective distribution of the insecticide, which is at the surface of the peat, where the eggs are laid and the newly hatched larvae will come in contact with the poison.

Adults of the cabbage root fly (Erioischia brassicae (Bch.)) fed on 0·1% tepa in 10% sucrose solution during the second and third days after emergence laid over 95% sterile eggs. Nearly complete sterility was also obtained from females fed on 0·l% tepa for two days between mating and oviposition. Tepa at 0·1% did not affect longevity of either sex or the competitiveness of treated males, although at higher concentrations longevity was reduced. When flies were enclosed in a large field cage and provided with food baits containing 0·1% tepa, sucrose and leucine along a hedgerow, 70% of the eggs laid were sterile.

To entomologists in India the three species of mango Jassids—Idiocerus niveosparsus, I. atkinsoni and I. clypealis—are fairly well known, both on account of their wide distribution and also on account of the serious damage they do to the mango crop. In the course of our studies on these important orchard pests we have within the past three years come across three natural enemies of the adult hopper and one of the nymph; These are (1) a Pipunculid fly; (2) a Stylopid—both internal parasites; (3) an Epipyropid moth—an external parasite of the adults: and (4) a Dryinid wasp—an external parasite of the nymphs.

A technique is described for counting the numbers of Pseudotheraptus wayi Brown on coconut palms, on which this Coreid is a serious pest in East Africa, Zanzibar and the neighbouring islands. The crown of each palm is systematically searched by an African assistant, the insects collected being classified by instars and then replaced. The adults can fly and very few are seen or captured.

Palms were examined by a team of searchers in five areas in a well-maintained plantation on Mafia Island, 3–4 separate samples, each of 61–138 palms, being taken in each area between mid-January and mid-February 1956. In all, 13 searchers participated, but not all were used on the same day; when they had become experienced their daily catches were of comparable size.

The total nymphal populations, and the proportions of them in the various stages, are sufficiently consistent to suggest that the searching technique may give reproducible results, and thus be of considerable value as a means of assessing the results of control measures.

The average catch was about one nymph for each palm that was searched, and recaptures from known numbers of bugs liberated indicated that about one quarter of the population present was being found. The nymphal population is not distributed at random among the palms.

Insecticidal aerosols dispersed from aircraft are used in control measures against Glossina spp., and the interpretation of spray monitoring data in terms of the likely effect on the flies requires some knowledge of variation of the collection efficiency of the flies under a range of appropriate conditions. A low speed wind tunnel was used to measure the collection efficiencies of the various component parts of an adult of G. morsitans Westwood when at rest on cylinders simulating the branches and twigs of the natural habitat. The wind speed range was from 0·25 to 1·5 m/s and monodisperse droplets 10, 15, 20 and 25 μm in diameter were used. Although certain body zones exhibited very high apparent collection efficiencies (primarily due to interception), the average overall efficiencies varied from as low as 0·8% for 10-μm droplets at 0·25 m/s up to 22% for 25-μm droplets at 1·5 m/s.

An account is given of the biology of the phytophagous Chalcidoid, Eurytoma sp. near howardi D.T., and of its bionomics in Mauritius. The insect was introduced into Mauritius from Trinidad to supplement the activity of the Galerucid beetle, Schematiza cordiae Barber, in the control of Cordia macrostachya, an introduced shrub, indigenous to Central America and the Caribbean Islands. The egg and larval stages are described and figured.

The entire development of Eurytoma takes place within the fruit of Cordia, which contains usually only one seed when mature and has a very hard and stony endocarp and a soft and fleshy mesocarp. Oviposition by Eurytoma takes place before the endocarp hardens; the egg is laid inside the seed and the larva feeds on the nucellus and endosperm and later on the developing cotyledons, until the entire seed, except for the seed coat, has been consumed. The attacked fruit continues to grow and its endocarp hardens, but final swelling of the mesocarp does not take place. Although more than one egg may be laid in a seed, only a small percentage of the many seeds dissected contained two mature larvae or two pupae. Pupation takes place within the seed, from which the adult escapes by boring a round hole through the endocarp.

Development from egg to adult occupies about 23 days in the hot season (November–April), but in the cooler months (June–September) the fully-grown larva enters a resting period, which may last several months.

Adults kept in jars, and provided with honey in water, at a mean temperature of 25°C, lived for an average of 11 days (males) or 20 days (females). A newly emerged female contains about 12 fully developed eggs. Virgin females oviposit readily, all the progeny being male.

Releases of adults from material received from Trinidad were made between October 1949 and May 1950; by the latter date it was evident that the insect had become established at the first liberation site and further colonies were established in various parts of the island from material collected there. Estimates of infestation of samples of fruit collected in October 1951 at or near 22 liberation points ranged from 16 to 81 per cent, (mean, 53·7). The latest island-wide estimates, in February, June and October 1953, showed averages of 64·7, 40·8 and 48·7 per cent, infestation, respectively.

Infestation of fruits is highest (70–80%) in the hot season, when fruit production is at its maximum, and lowest in the cooler months, when, although the rate of fruiting declines, the life-cycle of Eurytoma is prolonged.

Schematiza cordiae had achieved a high degree of control of Cordia before Eurytoma became widely established, and it is difficult to assess the contribution made by the latter, which has no known specific natural enemies in Mauritius; but the two unrelated insects acting jointly are likely to stabilise control more effectively than would one insect alone.

In an appendix, P. 0. Wiehe gives notes on the present ecological status of Cordia in Mauritius and contrasts it with that prevailing before the introduction of Schematiza and Eurytoma. He concludes that the secondary succession of vegetation has now reverted to its former course.

Numerous habitats were sampled for larvae of sheep headfly, Hydrotaea irritans (Fall.), in infested areas of Northumberland during the winters 1973–74 and 1974–75. Most of the larvae found came from near the surface of soil beneath pasture and long grass. The mean larval density in these sites was 1·93/m2; the greatest density in a single site was 3·87/m2 which compares well with unpublished estimates of adult fly density. Only two larvae were recovered from cow dung. One larva was found in bracken litter, and none in other types of litter, or in horse dung, peat, moss or rotten wood. Larvae were reared to the mid-third instar from eggs laid in the laboratory. Field-collected larvae fed readily on Musca and Calliphora larvae, and did not appear to diapause in December; their identity was confirmed by rearing them to the adult stage. The egg, second- and third-instar larvae, and puparium are described and figured. Descriptions are given of changes in the mouthparts during growth of the third-instar larva, and of the features by which field-collected larvae can be identified.

Screening of 38 selected juvenoids on Ceratitis capitata (Wied.) revealed that several aromatic compounds, mostly ethers of 6,7-epoxygeraniol and of 6,7-epoxycitronellol, inhibited hatching when administered to freshly laid eggs as 0·1% acetone solution. Application of juvenoids within 24 h before and after puparium formation caused disturbances in imaginal differentiation. Treated insects developed either into pupa-adult intermediates failing to emerge or into defective adults whose fecundity was severely decreased. Both earlier and later applications of juvenoids were less effective. The most active compound in topical assay on fully grown larvae was ethyl 10,11-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate, which inhibited emergence of 50% of treated insects at 0·01 μg/specimen and caused external deformities in 50% of emerged adults at 0·00001 μ/g/specimen. Four other aliphatic compounds (methyl 11-methoxy-3,7,11-trimethyl-2,6-dodecadienoate; ethyl 11-methoxy-3,7,11-trimethyl-2-dodecenoate; isopropyl 3,7,11-trimethyl-2,4-dodecadienoate; and isopropyl 11-methoxy-3,7,11-trimethyl-2, 4-dodecadienoate) and l-ethyl-4[(6,7-epoxy-3,7-dimethyloctyl)oxy] benzene were about five times less active. A concentration of 33 parts /106 of ethyl 10,ll-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate in larval food caused deformities in 60% of emerged adults.

Dung-colonizing beetles provide a range of ecosystem services in farmland pasture systems. However, such beetles are declining in Northern temperate regions. This may, in part, be due to the widespread use of macrocyclic lactones (MLs) and synthetic pyrethroids (SPs) in livestock farming. These chemicals are used to control pests and parasites of cattle; the residues of which are excreted in dung at concentrations toxic to insects. While the lethal effects of such residues are well known, sublethal effects are less understood. Any effects, however, may have important consequences for beetle populations, particularly if they affect reproduction. To investigate, the impact of ML and SP exposure on the reproductive output of Onthophagus similis (Scriba), a Northern temperate dung beetle species, was examined. In laboratory trials, field-collected adult O. similis exposed to the ML ivermectin at 1 ppm (wet weight) over a period of 3 weeks had smaller oocytes (p = 0.016), smaller fat bodies and reduced motility compared to the control. In a farm-level investigation, cattle dung-baited pitfall trapping was undertaken on 23 beef cattle farms in SW England, which either used MLs (n = 9), SPs (n = 7) or neither chemical (n = 7). On farms that used no MLs or SPs, 24.2% of females caught were gravid. However, on farms that used MLs no gravid females were caught, and only 1% of the beetles caught on farms using SPs were gravid (p < 0.001). The association between ML and SP use and impaired reproductive output suggests that the use of such chemicals is likely to be ecologically damaging.

The short-lived polygamous moth Grapholita molesta (Busck) is an important fruit pest worldwide. Trapping males by synthetic female sex pheromones is not an effective reproductive control strategy. It is important to improve this technology by understanding the mating system of G. molesta. This study investigated mating opportunities and fertile egg production by altering the operational sex ratio, mating age, and male mating history in repeated single mating and multiple mating in the two sexes. Our results showed that the mating and reproductive parameters of virgin males were affected by the number and age of virgin females. Males preferred a female number ≤three-fifths of the male number or ≤2-day-old females, while they discriminated against a female number ≥three times of the male number or ≥5-day-old females. On the other hand, the mating and reproductive parameters of virgin females were affected by repeated single mating and especially multiple mating under different male mating histories. Females preferred once-mated males and discriminated against virgin males. These results indicated that mating systems including more and older virgin females for virgin males and different virgin males for virgin females may be suitable for suppressing G. molesta populations. Hence, these results revealed that preventing mating of virgin adults by synthetic female sex pheromones should be most effective in controlling G. molesta.

Flower and leaf herbivory might cause relevant and negative impacts on plant fitness. While flower removal or damage by florivores produces direct negative effects on plant fitness, folivores affect plant fitness by reducing resource allocation to reproduction. In this study, we examine the effects of both flower and leaf herbivory by leaf-cutting ants on the reproductive success of the shrub species Miconia nervosa (Smith) Triana (Family Melastomataceae) in a fragment of Atlantic Forest in Northeast Brazil. We conducted a randomized block-designed field experiment with nine replicates (blocks), in which three plants per block were assigned to one of the three following treatments: undamaged plants (ant exclusion), leaf-damaged plants (ant exclusion from reproductive organs, but not from leaves), and flower + leaf-damaged plants (no exclusion of ants). We then measured flower production, fruit set, and fruit production. Our results showed that flower + leaf-damaged plants reduced flower production nearly twofold in relation to undamaged plants, while flower set in leaf-damaged plants remained constant. The number of flowers that turned into fruits (i.e., fruit set), however, increased by 15% in flower + leaf-damaged plants, while it slightly decreased in leaf-damaged compared to undamaged plants. Contrastingly, fruit production was similar between all treatments. Taken together, our results suggest a prominent role of ant floral herbivory across different stages of the reproductive cycle in M. nervosa, with no consequences on final fruit production. The tolerance of M. nervosa to leaf-cutting ant herbivory might explain its high abundance in human-modified landscapes where leaf-cutting ants are hyper-abundant.

The Mediterranean fruit fly Ceratitis capitata is a globally invasive pest, often controlled with the sterile insect technique (SIT). For the SIT, mass-rearing of the target insect followed by irradiation are imperatives. Sterile males are often less able to inhibit female remating and transfer less number of sperm, and even irradiation could affect male reproductive organs, with consequences for their ability to inhibit female remating. On the other hand, male age could affect their ability to modulate female response after mating. Here, we evaluated the quality of the genetic sexing strain Vienna-8-tsl mass-reared in Bioplanta San Juan, Argentina, under laboratory conditions, with regard to: (i) the ability of sterile males irradiated at 100 or 140 Gy to inhibit female remating, in the same day and at 24 h of first copulation; (ii) the ability of 3, 4 or 5 day-old sterile males to inhibit female remating at 24 h of first copulation, and (iii) the effect of a reduction in irradiation doses on the number of sperm stored by females and reproductive organ size in virgin males. Sterile males were better able than wild males to inhibit female remating in the same day of first copulation and as able as wild males 1 day after first copulation. Male age did not affect their ability to inhibit female receptivity. Number of sperm stored by females, testes size and ectodermal accessory glands size were not affected by male identity, while sterile 100 Gy males had larger mesodermal accessory glands than control lab males. A reduction in irradiation dose does not impact any variable measured, except for percentage of sperm-depleted females: females mated with sterile 100 Gy males had lower probabilities to store sperm. The results showed here are very encouraging for tsl Vienna 8 strain reared in Argentina and are discussed in comparison with previous studies in C. capitata female remating with dissimilar results.

The discovery of a species of Phlebotomus in Australia is of considerable interest in view of the fact that the genus contains several exotic species known to be the vectors of specific fevers in man (verruga, pappataci fever, etc.).

The four components of the synthesised sex pheromone of Diparopsis castanea Hmps. are dodecan-1-yl acetate (I); trans-9-dodecen-1-yl acetate (IIA); 11-dodecen-l-yl acetate (IIB); and trans-9,ll-dodecadien-l-yl acetate (IV). Increasing the proportion of IIA in a I/IIA/IIB/IV mixture progressively decreased male excitation in a laboratory bioassay, whilst in the absence of I all concentrations of IIA tested were equally inhibitory. The synthetic combination of 80% IV (93% trans: 7% cis) and 20% IIB (=dicastalure), was 485 times more potent in eliciting male activity than a female sex pheromone gland extract. Reduction in male response to crude extract occurred through exposure of males to glandular IIA and through reduced pheromone volatility caused by extracted triglycerides. Maximum quantities of pheromone were detected in the female sex pheromone gland 6–12 h into scotophase and for at least 30 min into photophase. Significantly greater bioassay responses were elicited by the optimal field combination of 80% IV and 20% IIB than for other ratios tested. Excitation and clasper extension were observed in response to the non-attractive IIB moiety and this indicates a role in close-range mating behaviour for this component. The threshold level of male response was estimated to occur in response to sex pheromone at an aerial concentration of 9·2 molecules IV mm3/s−1. This suggests that aerial concentrations of 102–103 times the male threshold response level may be sufficient to cause successful communication disruption in the field. The problems of relating the non-oriented responses in an assay of this type to directional responses in traps are briefly discussed.

Following the introduction and establishment of Rhabdionvirus oryctes in Mauritius, seven adults of Oryctes rhinoceros (L.) were found with external malformations ranging from slight deviation at the base of the elytra to almost complete atrophy of the wings and elytra. Histological abnormalities of the midgut are described from a sample of 46 beetles of which 36 proved to be infected; infected epithelial cells are discharged into the gut lumen and so into larval and adult habitats.

Blosyrus aequalis, Har. 1879.

This species, originally described from Angola, has recently been bred from larvae found in tubers of sweet potatoes at Haut-Lepori, Belgian Congo, by Lieut. J. Ghesquière.