Field studies on the biting habits of Culicoides furens (Poey) were made near Montego Bay, Jamaica, during 1959 and 1960. Details of the experimental design and analysis have been given in the preceding article of this series. C. furens was collected in eight experiments, six on Florida beach, one at East Florida and one at White Bay. Four of the experiments were conducted at sunset, three at dawn and one in the night.

This paper reports the results of a field experiment on Florida beach, Falmouth, Jamaica, in which continuous observations were made on the biting rates of Culicoides furens (Poey) (7 707 specimens) and C. barbosai Wirth & Blanton (3 793 specimens) over two 48-h sessions in January 1960. Catches were standardised by the use of correction factors previously calculated. The standardisation experiments also provided additional information on parts of the 24-h cycle, particularly sunrise and sunset.

The effects of DDT on the behaviour and mortality of Anopheles gambiae Giles, A. funestus Giles, Mansonia uniformis (Theo.) and Culex pipiens fatigans Wied., entering experimental huts, have been studied with the assistance of gas-chromatographic techniques.

Sixty to 70% of A. gambiae and 70–80% of M. uniformis were deterred from entering verandah-trap huts treated indoors with a nominal dosage of 200 μg/cm2 of DDT active ingredient. Gas chromatographic techniques indicate that the chemical basis of the deterrency was a steadily diminishing outflow of DDT from the hut, either as a dust or vapour, and the build-up of deposit on the untreated overhanging eaves to 0·02 to 0·27 μg/cm2 seven months after treatment. A. funestus was less deterred than A. gambiae and M. uniformis, but the behaviour of C. p. fatigans was almost unaffected by the DDT deposit.

Overall mortalities were highest in A. funestus and M. uniformis, lower in A. gambiae and extremely low in C. p. fatigans.

There was a marked irritant effect of the DDT deposit on recently blood-fed A. gambiae, some 50–70% being driven out of the treated huts. This behaviour occurred to a lesser degree in A. funestus but was absent in M. uniformis and C. p. fatigans. The chemical basis of the irritant effect was indicated to the extent that surviving mosquitoes, that left the treated hut, showed 1·5 ng/insect of DDT. Mosquitoes that died, whether indoors or after leaving the hut, picked up amounts ranging from 7 to 20 ng/insect.

Seasonal changes in two natural larval populations of Leptoconops becquaerti (Kieff.), a biting sandfly of economic importance in the Caribbean area, are described from studies in 1963–64 near Montego Bay. Aspects of the ecology arising from these observations are included. An attempt is made to relate the seasonal changes in the larval populations to the seasonal distribution of adults, and in addition, a separation is made between the autogenous and anautogenous forms of the insect.

Larvae of both autogenous and anautogenous forms lived together in the same breeding sites and did not appear to differ in their spatial distribution. The two populations studied consisted mainly of larvae associated with the small, autogenous form. Drastic reduction in both populations occurred following events such as wave action and heavy rain that had a mechanical action on the sand in which the larvae lived. The distribution of both forms of larvae was dependent upon the surface elevation with respect to the level of free soil water, since this to a large extent, owing to the upward capillary movement of water, governs moisture content of the surface sand. Elevations between about 9 and 17 in. appeared to be the most favourable. Permanent breeding probably does not occur in sand at elevations greater than about 21 in., though temporary breeding may occur at higher elevations if some other source of moisture (e.g., frequent rain) is available.

In the autogenous form, a prolonged period was spent in the third larval instar. This was probably induced by some factor associated with lack of moisture in the sand, and appears to be broken (causing completion of development) by an effect of increased moisture content after heavy rain. This phenomenon probably does not occur in the anautogenous form.

Earlier studies of crop loss following insect attack on cotton in the elephant-grass zone of Uganda were followed up for two more seasons (1965–67), using large plots and routine spray schedules with different insecticides. The spray schedules were four or six fortnightly applications of insecticide, beginning at week 8 from emergence in the 1965–66 season, and four fortnightly or eight weekly sprays in the 1966–67 season. The insecticides used were DDT, endrin and dicrotophos in the first season and DDT, endrin and endosulfan in the second.

Estimates of Taylorilygus vosseleri (Popp.), Heliothis armigera (Hb.), Earias biplaga Wlk., Cryptophlebia leucotreta (Meyr.), Pectinophora gossypiella (Saund.), Dysdercus spp., Aphis gossypii Glov., Tetranychus sp. and Eotetranychus sp. showed that, although one or other of the insecticides reduced the different pests to very low levels, yield increases were not obtained. In the 1966–67 trial, when the more important pests were present in very low numbers, DDT and endosulfan significantly reduced yields of clean seed cotton and it is suggested that these formulations are slightly phytotoxic to Uganda cottons.

The relationship between the shedding of fruiting bodies and the harvesting of the crop showed that sprays applied after week 14 did not affect the total crop in any way. Increased soil fertility caused the plants to form more fruiting bodies and, although many of these were shed, a higher proportion were retained with or without protection from pest damage.

It is concluded that the pest damage is too light to affect yields of early-sown cotton where varieties of indefinite growth habit can compensate for early loss of fruiting bodies in the extended growing season. Routine spraying gives no benefit and, in some seasons, can be harmful.

Two species of Lepidoptera reared from galls caused by a Thysanopteran, Vuilletia houardi (Vuillet), on the shrub Guiera senegalensis (Combretaceae) in Northern Nigeria are described as new. One is named Eublemma guiera sp. n. and belongs in the subfamily Eustrotiinae of the Noctuidae, and the other Anarsia guiera sp. n. and belongs in the Gelechiidae. The adults and male and female genitalia of both species are illustrated.

A chemical sex attractant for the male grass grub beetle (Costelytra zealandica (White)) has been shown to be present in a commercially available adhesive preparation.

Oryctes rhinoceros (L.) breeds in the rotting stumps of oil palms and rubber trees, and is a potentially devastating pest of young oil palm replants, the unopened leaves of which are attacked by the adults. In view of the planters' belief that the pest is controlled by heavy ground vegetation, the effects of cover (natural, legume or grass) and bare ground on beetle populations in rotting logs and incidence of beetle attack on young palms were compared in a series of four experiments.

A new species of scale insect from coconut trees in Trinidad is described and named Parlagena bennetti. The generic assignment is tentative. A key to the four known species of Parlagena is provided.

A new species of Cataenococcus Ferris, C. larai, is described from material obtained from banana fruits in Costa Rica. A key is provided to the five known N. American species of Cataenococcus.

The identity of the Lymantria species in the north-western Himalayas is confirmed as L. obfuscata Wlk., and not as L. dispar (L.) with which it has commonly been confused in the past. The larval and imaginal characters separating the two species are described and illustrated.

Experiments were carried out to remove existing doubts about the toxicity (and therefore cost per unit killing power) of malathion to adults of Schistocerca gregaria (Forsk.) which have arisen from earlier field and laboratory tests. Malathion is shown to be almost as toxic to these insects as γ-BHC, but superior in speed of action. These observations are in agreement with the performance of these two compounds in the field.

Subdivision of a dose of malathion with simultaneous application at two loci increased its toxicity. This, as well as other factors, brings the value of LD50 determinations into question. Recommendations for large-scale use of new insectsicides, based only on laboratory data, may not always be reliable.

Despite strict standardisation of cultural and bioassay procedures, significant results were attained with difficulty because of great variation in mortalities of batches of adult Ptinus tectus Boield. exposed to insecticide deposits. In tests using lindane, the variation between weekly batches was reduced by selecting beetles within the weight range 1·8–2·4 mg, but variation between replicates in a batch was unaffected. This latter variation was found to stem both from the weights and from the sexes of the beetles; in general, heavier beetles were less susceptible than lighter ones and females were less susceptible than males at comparable weights.

A species of Dioryctria reared from Pinus kesiya (= khasya) at Shillong, Assam, where it is found in association with D. abietella (Schiff.) and D. sylvestrella (Ratz.), is described as new and is named D. castanea sp.n. The distinctive purplish or reddish chestnut brown coloration of the forewings is considered to distinguish this species from others in the genus. Illustrations are given of the adult and of the male and female genitalia.

Female Musca vetustissima Wlk. may be allocated to one of seventeen classes of development between emergence and the start of the fourth ovarian cycle, the criteria being the amount of pupal fat body, but chiefly the presence and size of the follicular relics (yellow bodies and beads in the ovaries) during successive ovarian cycles. The duration of these cycles was estimated under standard and differing environmental conditions. Withholding protein for up to two weeks merely delayed the first ovarian cycle, but longer deprivation caused reduced fertility. The initial phase of the first ovarian cycle was independent of protein feeding, but a protein feed was necessary to complete the cycle, and a further protein feed was needed to complete the second ovarian cycle. No development in the first cycle took place below 57°F, but between 58 and 78°F development was progressively faster. Unfertilised females developed and laid the first batch of eggs, but were unable to complete a second batch. Oviposition was delayed by lack of favourable sites, and after one week fertility was progressively reduced. It is shown that, because of these variables, valid estimates can be made only of the minimum age of female bushflies.

Observations were made on the bionomics of Spodoptera mauritia acronyctoides Gn. in Malaysian Borneo (Sarawak) during an outbreak in 1967. The outbreak was discontinuous over about 6 000 sq. miles, affecting 25 000 acres of lowland and upland rice. In the insectary the durations of the various stages were: egg 2·9 days, first- to seventh-instar larvae respectively 3·1, 1·8, 2·2, 2·1, 2·2, 2·3 and 4·9 days, and pupa 8·4 days. Larval instars could usually be distinguished on head width and the width of the faecal pellets. Food consumption of the larvae was greatest during the final instar. During the outbreak the larvae were found mainly on young rice, and also on young maize; wild host-plants included grasses and sedges, but dicotyledonous plants were not attacked.

Females generally mated on the night following emergence, and the pre-oviposition period averaged 2·9 days. Fertilised females laid an average of 1 749 eggs, 80% of the potential total. Virgin females laid only 22% of the potential, and resorbed some of their oocytes. The mean longevity of fertilised females was 5·5 days. Fecundity was directly correlated with pupal weight or length, and the weights of pupae produced in wet-rice fields were significantly heavier than those from dry hill-rice sites. There was a significant correlation between the weight of frass produced (hence food consumed) by the seventh-instar larva and the weight of the pupal stage. Pupae from larvae in crowded cultures were significantly lighter than those reared singly.

Ecological studies were undertaken from 1964 to 1966 on the mosquitoes that occurred in the Poole area of Dorset, southern England. The seasonal incidence was obtained of adults of Aedes cinereus Mg., Ae. punctor (Kby.), Ae. cantans (Mg.), Ae. detritus (Hal.), Culiseta annulata (Schr.), Mansonia richiardii (Fic.) and Anopheles plumbeus Steph. There were marked annual variations in their populations. With the exceptions of Ae. cinereus and Ae. cantans, their diel biting cycles were obtained. In most species maximum biting occurred around sunset and sunrise, with a reduction in biting at night. A comparison was made of the biting times of Ae. detritus and M. richiardii at sunset and sunrise in July and August. By dividing the catch into five-minute intervals peak biting times were related to crep values.