1. The investigation which forms the subject of this paper was commenced in 1936 and closed in 1939. Owing to the low returns from an acre of coconut land it was imperative that control measures should be cheap. Biological methods were therefore employed.

2. The soils on which coconuts are planted in Seychelles fall into three main types: (a) beds of coral sand, (b) various types of transported soils, (c) sedentary soils.

3. The robustness of the trees was found to be in direct proportion to the quality of the soil. The best trees are located on the deeper alluviums. The limiting factor on the coral sands is often drainage. On the hill-sides the trees deteriorate in proportion to the soil impoverishment and erosion.

4. A complex of scale species attack coconuts in Seychelles. None of these presents major problems in other countries, and the better known scales which are pests on this crop in other countries are not found in Seychelles. Four major species are mentioned, two of which are recent introductions to the islands. The life-history and particular requirements of each species are given and their incidence on coconut and their interspecific relationships are discussed.

5. In order to combat these scales four species of Coccinellidae were introduced from East Africa, two of which were predators on Diaspid and two on Lecaniid scales. The life-history, breeding technique and establishment of each is described.

The result of treating Tenebrio molitor L. pupae with synthetic juvenile hormone (JH) or a juvenile hormone analogue, methyl farnesoate dihydrochloride (DMF), is to arrest pupal development, producing pupal/adult intermediates. Both substances induced approximately 50% pupal/adult intermediates at a topically applied dose of 1 μg. The activity was greatly affected by the age of the pupa at the time of treatment, one- and two-day-old pupae being the most sensitive. Applied to four-day-old and older pupae complete metamorphosis to the adult was possible at a dose of 8 μg of synthetic JH and up to 200 μg for DMF. Doses above these levels merely increased toxicity without juvenilising activity.

With the new material received from the Imperial Bureau of Entomology through the courtesy of Dr. Guy A. K. Marshall, I am now able to complete my previous notes on the Ethiopian Trypaneidae.

Chitinases have an indispensable function in chitin metabolism and are well characterized in numerous insect species. Although the diamondback moth (DBM) Plutella xylostella, which has a high reproductive potential, short generation time, and characteristic adaptation to adverse environments, has become one of the most serious pests of cruciferous plants worldwide, the information on the chitinases of the moth is presently limited. In the present study, using degenerated polymerase chain reaction (PCR) and rapid amplification of cDNA ends-PCR strategies, four chitinase genes of P. xylostella were cloned, and an exhaustive search was conducted for chitinase-like sequences from the P. xylostella genome and transcriptomic database. Based on the domain analysis of the deduced amino acid sequences and the phylogenetic analysis of the catalytic domain sequences, we identified 15 chitinase genes from P. xylostella. Two of the gut-specific chitinases did not cluster with any of the known phylogenetic groups of chitinases and might be in a new group of the chitinase family. Moreover, in our study, group VIII chitinase was not identified. The structures, classifications and expression patterns of the chitinases of P. xylostella were further delineated, and with this information, further investigations on the functions of chitinase genes in DBM could be facilitated.

Digonogastra kimballi sp. n. and D. solitaria Wharton & Quicke sp. n. are described from Texas and Mexico. They attack stalk-boring pyralids in a variety of gramineous plants, including maize, sorghum and sugarcane. Known hosts are Eoreuma loftini (Dyar) and five species of Diatraea.

The taxonomy of species in the braconid subfamily Microgastrinae that parasitize the larvae of Diatraea in the New World is reviewed and a brief diagnosis of each species provided. Apanteles fredi sp. n. is described from Guatemala and its relationships discussed. Information on the distribution, host associations and range in variation of species is provided, along with a revised and illustrated key to facilitate their identification.

Like the preceding instalment, this part deals mainly with species bred on the West Coast of Africa. I have to thank Dr. L. Masi, of Genoa, for fig. 4, illustrating the wing base of Eusemion italicum, Masi.

The Rothamsted Insect Survey has kept records of aerial aphid activity using suction traps since 1965. Previous work has shown that, for certain species, there is a linear relationship between the date of first record in the trap each year and the mean temperature during the preceding winter. This paper describes and evaluates a more complex technique which relates the date of first record to a range of weather variables over 28 winter time periods. The technique uses principle components analysis to remove correlations between weather variables before these are regressed on the date of first record. Data from 1966 to 1988 inclusive are used to generate models to predict the date of first record of Myzus persicae (Sulzer) at Rothamsted, and the predictive values of models using both simple and multiple regression are assessed using data from 1989 to 1992. The accuracy of the multiple regression models was no greater than that of the simple regression models during these years. However, the multiple regression approach identified relationships with other variables for time periods when the correlation with mean temperature was weaker and may therefore be more widely applicable.

This parasite approaches Neumann's Haematopinus (Polyplax) maniculatus, but is immediately recognised by the truncate proboscis, by the “ olecranon process ” of the hind pair of legs, and by the remarkable “ comb ” which terminates the abdomen of the ♀. Perhaps a new genus should be made to receive it.

Linear, abdomen about four times the length of the head and thorax together. Head very broad, proboscis truncate, its lateral margins diverging to as far as the antennae, behind which the head enlarges at right angles. Post-antennal area rectangular, broad ; the occipital margin a little convex. At each posterior angle a long hair ; on the under surface, at about the level of the antennae, two short bristles, one on each side. Antennae of five segments, the first being thick and stout, the second narrower and the longest, the third short, and the fourth broad with a sharp prominence at the post-axial distal corner. Adjoining the prominence a small circular sense-organ which crosses the joint and occupies part of the base of the terminal segment. The latter is longer than the third or fourth, and has several spines at the end. Thorax broader than the head and broader behind than in front. A large flattened spheroidal spiracle at each lateral margin.

Athalia lugens subsp. proximo (Klug) is a pest of cruciferous crops, and shows special preference for turnip. In the matter of selection of food, smell and taste of the food and the age of the plant are important factors. Epilachna vigintioctopunctata (F.) is a pest of solanaceous plants, particularly brinjal. In this insect only smell and taste are important factors in the selection of food.

The hydrogen-ion concentrations of the salivary gland, foregut, midgut and hindgut of the larva of Athalia are 6·4–6·6, 6·4–6·8, 6·6–6·8 and 7·0 and of the adults 6·2–6·4, 6·4–6·6, 6·4–6·6 and 6·6, respectively. The hydrogen-ion concentration of the salivary gland, foregut, midgut and hindgut of the larvae of Epilachna are 5·4, 6·4–6·8, 6·0 and 6·0 and of the adult 6·6–6·8, 6·2, 6·0 and 5·4–5·7, respectively.

The foregut and hindgut of the larvae and adults of Athalia and Epilachna do not secrete enzymes; the salivary glands of both larva and adult of Athalia secrete amylase, the midgut epithelium of both larva and adult of Athalia secretes amylase, maltase, invertase, lactase, lipase and protease. The salivary glands of the larva of Epilachna secrete amylase, but those of the adult do not, and the midgut epithelium of both larva and adult secretes amylase, maltase, invertase, lactase and protease. The midgut of both larva and adult of Epilachna secretes lipase also, although in the adult no more than traces are detectable. The proteases in both insects act in slightly acidic media.

Adults of Calandra granaria and C. oryzae have been fumigated with hydrogen cyanide by the methods of sustained pressure reduction and preliminary pressure reduction, the main criterion of response being death. Of the factors studied, starvation and sex of the insects are without influence. With pressure reduction, Haber's Rule relating mortality, concentration and period of exposure is not followed; for a given concentration-time product, the mortality is higher, the shorter the period of exposure.

Preliminary pressure reduction increases mortality much less than sustained pressure reduction. With the latter the mortality of C. oryzae is higher than that of C. granaria. The increases in susceptibility are largely accounted for by increases caused by pressure reduction alone in the absence of fumigant. The number of eggs laid by untreated females and by females surviving treatment was excessively variable and no discrimination between factors could be made.

Ochlerotatus albifasciatus is a vector of western equine encephalomyelitis in Argentina and a nuisance mosquito affecting beef and dairy production. The objective of this study was to analyze whether environmental proxy data derived from 1 km resolution NOAA-AVHRR images could be useful as a rapid tool for locating areas with higher potential for Oc. albifasciatus activity at a regional scale. Training sites for mosquito abundance categories were 3.3×3.3 km polygons over sampling sites. Abundance was classified into two categories according to a proposed threshold for economic losses. Data of channels 1, 2, 4 and 5 were used to calculate five biophysical variables: normalized differences vegetation index (NDVI), land surface temperature, total precipitable water, dew point and vapour saturation deficit. A discriminant analysis correctly classified 100% of the areas predicted to be above or below the economic threshold of 2500 mosquitoes per night of capture, respectively. Components of the NDVI, the total precipitable water and the dew point temperature contributed most to the function value. The results suggest that environmental data derived from AVHRR-NOAA could be useful for rapidly identifying adequate areas for mosquito development or activity.

In the Sudan Gezira, some 240,000 feddans of Egyptian-type cotton (Gossypium barbadense) are grown annually by gravity irrigation from the Sennar Dam, and this is sprayed with DDT, 6–10 weeks after sowing, in order to control the cotton jassid, Empoasca lybica (de Berg.), which is considered to reduce the yield. The seasonal yield response to DDT was estimated by comparing the yields of single sprayed and unsprayed 90-feddan fields, pairs of which were selected in each of the 40 (now 44) Blocks into which the cotton estate cropped by the Sudan Gezira Board is divided for administrative purposes. In order to establish that this estimate adequately represented that of the estate as a whole, it was necessary to show the validity of three assumptions: that the sample was representative; that the unsprayed plots, though surrounded by sprayed cotton, were sufficiently large to behave in respect of yield as if their environment had not been sprayed; and that the selection of the fields was effectively at random.

Examination of the yield history of the fields that were sprayed showed that there had been a slight bias towards the selection of fields that yielded better than the mean of the locality, and although this bias did not change from place to place or year to year, it did increase with level of yield. It is not, however, considered big enough to invalidate the first assumption.

The second assumption was tested by a special experiment reported elsewhere, which produced no evidence to suggest that a 90-feddan field would be affected in respect of yield and insect pests by proximity to a differently treated neighbouring field.

The third assumption cannot be proved, but during two seasons when fields were selected by a random procedure, the results did not differ seriously from those in years when the choice was not completely random. Moreover, when the yields of fields selected for treatment in one year were examined for the season when the fields were last cropped with cotton, and spray treatments were identical, they were found not to differ significantly, although the differences were increased and became significant in the year when sprayed and unsprayed treatments were applied.

Accordingly, the yield of the unsprayed sample is taken to indicate what the yield of the whole estate would have been had all the cotton been unsprayed.

The yield response to DDT spray of Gezira cotton, as thus estimated over the period 1949–50 to 1956–57, was shown to vary from season to season. A highly significant part of this variance was correlated with the amount of ram falling in July, some six weeks before the crop was sown, but the response was also significantly affected by both seasonal and site effects that were also correlated with this early rain. A series of experiments in 1956–57 showed that Domains Sakel cotton, which is grown in the drier, northern part of the Gezira, tended to give an increased response to DDT spray at higher levels of nitrogenous fertiliser, and that a very highly significant part of this response was due to the control of jassid, E. lybica, and thrips, (Caliothrips spp.). X1730A, grown in the wetter, southern part of the Gezira, gave no over-all response to spraying, nor was the response to nitrogenous fertiliser affected by spraying. When the yields of these varieties were examined separately over eight seasons, it was found that Domains Sakel gave a mean yield response to spraying of 1·11 kantars of seed cotton per feddan, which did not vary significantly from season to season, but that X1730A gave a yield response which was less when pre-sowing rains were good and nitrogenous fertiliser was applied. Although the regression on July rains and on fertiliser of the response of X1730A to spray failed to reach significance at P = 0·05, it is considered that further data should enable a prediction of yield response of X1730A to DDT spray to be made by examination of these two factors.

Since 1935–36, yields of cotton in the Sudan Gezira have been positively correlated with the amount of rain falling between 1st July and 15th August of the year of sowing. Comparison of the coefficient of regression of yield on this rainfall in the period (1935–36 to 1947–48) before sprays or fertiliser were applied, with that of a more extended period (1935–36 to 1954–55) including six seasons in which sprays and fertiliser were applied, shows that the latter is only about one half the former. After allowing for differences in varietal response to spraying and fertiliser, it can be shown that this decrease in the deleterious effect of a deficiency in pre-sowing rains, is almost exactly accounted for by the beneficial effect of DDT spray.

It is concluded that at least half of the deleterious effect of poor pre-sowing rains on Gezira yields is a pest effect which can be eliminated by DDT spray.

The study thus provides a means whereby DDT spray may be applied selectively to those areas of the Sudan Gezíra where its effect is likely to be most profitable and suggests, moreover, that such a policy would reduce the considerable seasonal fluctuations in cotton yields which in the past have characterised cropping in this area.

The genus Leptoconops was erected in 1890 by the Australian dipterist Skuse for a minute black Chironomid fly which he captured at Woronora, near Sydney, New South Wales. This genus he placed in the last of the three sections into which he divided the family Chironomidae, namely, the Ceratopogonina. The fly greatly resembled a small species of Simulium in general facies, and presented certain peculiar characters which rendered it strikingly distinct from other members of the section. Indeed, certain authors (Mik 1894, Johannsen 1905) have since drawn attention to the marked similarity in the wing venation of an American species (L. torrens, Twns.) and Corynoneura, a genus of the subfamily Chironominae. Later (1907) Noé suggested the formation of an additional subfamily—Leptoconopinae—for the Australian and allied species (at that time classified in three genera), and Malloch (1915), although acknowledging that the genus Tersesthes, Twns. (a synonym of Leptoconops), was unknown to him, associated it with the Chironominae rather than with the Ceratopogoninae. Apart from the wing venation, however, Leptoconops shows no affinities with Corynoneura, but rather agrees with the Ceratopogonine midges, particularly in regard to the structure of the thorax and mouth-parts. Several species of Leptoconops have now been described, but owing to differences in the interpretation of, or slight variations in, some of the generic characters given by Skuse, as well as to subsequent descriptive errors, they have, in greater part, been referred to the genera Tersesthes, Twns., and Mycterotypus, Noé. As was to be expected, however, the close agreement exhibited in the diagnoses of these genera and of Leptoconops has caused several authors to suggest their identity; but indefinite or partial conclusion* only were reached, since the genotype of Leptoconops (L. stygius, Sk.) was not re-examined.

The silk derived from the cocoon-masses woven by the larvæ of Anaphe infracta, Wlsm., A. venata, Butl., A. moloneyi, Druce, and others of the same or an allied genus of the family Eupterotidæ, is utilised in the Haussa and Yoruba countries of Northern and Southern Nigeria for the manufacture of yarns, used in the embroidery of Haussa gowns in the former country and, in conjunction with cotton in the latter locality, for the production of the “ sanyan ” cloths.

During the years 1925–7 an investigation was made of the Culicine mosquito fauna of Singapore, mainly with the object of learning which species were responsible for the local mosquito plague, and where they bred. In the course of this work numerous species were reared, the larvae of which have never been described, and descriptions of these are presented in this paper; these are supplementary to the descriptions published recently by Edwards (Bull. Ent. Res. xvii, pt. 2, 1926).

During the past 12 years, records of beetles of the family Ptinidae as pests of stored products in Britain have been increasing in frequency. Kloet & Hincks (1945) record 21 British species of Ptinids, but of these, three species, Ptinus palliatus, Perris, P. pilosus Mueller and P. latefasciatus Gorh., have not so far been recorded from warehouses or stored products and a furthertwo species, P. lichenum Marsh. and P. subpilosus Sturm have only rarely been recorded from such habitats. The importance of birds' nests as reservoirs of pests of stored products is being shown in a paper to be published shortly by Woodroffe and Southgate who carried out a survey of the fauna of the nests of birds associated with buildings. They found that the fauna of such a habitat was extraordinarily similar to that of warehouses in this country and that very large numbers of several species of Ptinids were present. The risk of this habitat being a possible source of many Ptinid infestations can be gleaned from the following list of species which they found:—

Ptinus tectus Boield., P. fur (L.), P. sexpunctatus Panz., P. pusillus Sturm, P. subpilosus Sturm, Eurostus hilleri (Reitt.), Niptus hololeucus (Fald.), Mezium affine Boield., Trigonogenius globulus Sol.

Sweet corn (Zea mays) is frequently attacked by Oscinella frit (L.) in southern England because the optimal sowing date (1st–20th May) determines the appearance of the seedlings at the peak of the spring flight (13th–30th May).

A Latin-square experiment including three Thimet treatments and controls showed that almost complete protection could be given by seed-furrow and surface placements along the rows of an 8 per cent, granular formulation at the rate of 2 lb. actual Thimet per acre.

The crop on the untreated control plots was more than halved by the naturally occurring infestation of 45 per cent, of the primary shoots.

Estimation of Thimet residues in cobs taken from the seed-furrow treatment showed that only a very minute trace of toxic material was present.

Tasting tests on cobs from treated plots revealed no detectable taint.

Drought is the only factor in the environment of the eggs of Austroicetes cruciata that is likely to cause a high mortality rate of the eggs in the field.

The eggs may be exposed to drought at various stages of their development. The probability of high mortality due to exposure to drought during the winter is considered to be negligible.

The probability of a high mortality rate due to drought when the nymphs are hatching is unimportant. From an analysis of the meteorological records for 50 years, it was estimated that high mortality rates from this cause may occur 12 times in a thousand years at Hawker and less frequently elsewhere in the grasshopper belt.

The eggs are exposed to the most severe hazards during the summer. An analysis of the meteorological records shows that severe mortality rates may have occurred as a result of drought in the summer from one to seven times during the 50 years 1891–1940, depending upon the district.

Five flavonoids from hops, two of their derivatives, along with naringenin used as a model compound, were tested for their antifeedant activity against three coleopteran stored product pests: Sitophilus granarius L., Tribolium confusum Duv. and Trogoderma granarium Everts. The introduction, into the tested flavonoid molecules, of additional structural fragments such as prenyl or dimethylpyran moiety, is proposed to significantly alter the deterrent activity of the compounds. The prenyl moiety in flavonoids increased the deterrent activity of these compounds in all three of the grain feeding species used in the tests. It is also concluded that the introduction of dimethylpyran moiety to the flavonoid structure increases its deterrent activity in S. granarius and T. confusum, but in one of the test insects, T. granarium, an increased feeding was observed in response to the introduction of dimethylpyran moiety to the flavonoid structure.