Records of termites attacking growing crops in Saudi Arabia have so far referred to Microcerotermes diversus Silv., one of the subfamily Amitermitinae of the Termitidae (Ayoub, 1959). This termite is also known from the Yemen, the South Arabia Federation and Iraq.

The toxicity and persistence under natural field conditions of deposits of dieldrin and isobenzan, derived from dilutions of emulsion concentrates, on the leaves of riverine vegetation in the Northern Guinea Savannah vegetation zone of Nigeria were studied by a bioassay method, using teneral females of Glossina palpalis (R.-D.) as test insects. Although deposits of both insecticides were extremely toxic when first sprayed, neither product was found to have a long residual action, and isobenzan was found to be approximately half as efficient as dieldrin. It is suggested that because of its poor residual action isobenzan will be little used in tsetse control campaigns in areas similar to that in which the investigations were performed.

Crops of cowpea (Vigna unguiculata) in Northern Nigeria are normally subject to such heavy attack by insects that the potential yields are seldom realised. The most important pests are Maruca testulalis (Geyer), which damages flowers and pods, Piezotrachelus varium (Wagn.), which attacks seeds, and the Coreids Acanthomia brevirostris Stål, A. horrida (Germ.), Anoplocnemis curvipes (F.) and Mirperus jaculus (Thnb.), all of which destroy pods. Pests that attack the pre-flowering stages of the cowpea are economically less important. Field surveys showed that, in 1961, Maruca testulalis, P. varium and Coreids together destroyed 62, 92 and 19 per cent, of the potential crop of seed from sowings in June, July and August, respectively. The corresponding percentages for 1962 were 55, 75 and 29, respectively.

The effectiveness of insecticides in the control of the pests that attack after flowering has commenced was investigated in field trials at Samaru, Northern Nigeria, in 1961–63. The results showed that large increases in yield could be obtained by spray treatments starting at the first appearance of the flowers. The best of these, consisting of 1 lb. DDT with 0·1 lb. BHC per acre applied six times at weekly intervals, gave an average yield over the five trials of 1,623 lb. dry seed per acre, which is a substantial increase over the estimated national average of 158 lb. per acre. Three applications of DDT/BHC, and six or three applications of Sevin at 1 lb. per acre, gave poorer results on the whole. Insecticidal treatment reduced the incidence of all pests and led to a corresponding reduction in flower losses. It also compressed the flowering period, induced earlier flowering and pod production, and caused the bulk of the crop to mature at one time. Haulm production was also reduced, and crops grown for haulms rather than for seed should therefore not be treated with insecticides.

The insecticidal potencies of γ-BHC and a range of chlorinated cyclodiene compounds have been measured for normal and resistant strains of both Musca domestica L. and Lucilia cuprina (Wied.). Apart from minor discrepancies, the relative potencies presented similar pictures in the two species, and the resistance spectra were also similar.

Moderate to high insecticidal potency is shown by a variety of compounds with a chlorinated bicyclo-heptene nucleus in the molecule, including Diels-Alder condensation products and chlorinated camphenes. Various additions and sub-stituents on the nucleus affect the potency quantitatively but not qualitatively. In contrast, γ-BHC is almost unique among poly-halogenated cyclohexanes.

When resistance develops to any of the chlorinated cyclodiene compounds, it invariably extends to all others and to γ-BHC and chlorinated adamantane. The resistance level, in most cases, is proportional to the original potency of the compound; this is apparently because resistance is usually complete, so that the more toxic compounds have more to lose. There are, however, a few puzzling exceptions.

The consistency of the cross-resistance spectrum to all members of the group implies a common defence mechanism. This suggests a common mode of toxic action, resistance being due to insensitivity at the site. A common mode of action for the cyclodiene series is understandable; the anomalies are γ-BHC and chlorinated adamantane. Their conformity with the cyclodiene insecticides was investigated by the following observations with normal insects: (a) signs of poisoning; (b) relative potency to different species; (c) tests with mixtures. The general conclusions were not unfavourable to the hypothesis of a common mode of action, though secondary features of the intoxication process somewhat complicated the results.

A key is given for the separation of a group of allied species of Eulophidae comprising Elachertus nigritulus (Zett.), E. geniculatus (Eatz.), E. olivaceus (Thoms.), E. scobiciae Erdős, and a species here described as E. pallidus sp. n. Biological data for each species are given. E. nigritulus and E. geniculatus have previously been regarded as synonymous; the latter parasitises Laspeyresia strobilella (L.), a pest of conifers, whereas E. nigritulus, and also E. pallidus, attacks Lepidoptera associated with fruit trees.

The influence of a deep river valley system on the distribution of dispersing Aedes mosquitos was studied during 1958–59 in the vicinity of Edmonton, Alberta, Canada. Mosquito breeding within an area extending two to three miles beyond the city limits was prevented by anti-larval measures, and almost the only remaining breeding places were situated on the plains several miles to the north-west and south-east, yet considerable numbers of mosquitos appeared every spring in that part of the city included in the valley-ravine system of the North Saskatchewan River. Previous work had suggested that mosquitos dispersing across the plains were collected by the valley-ravine system and entered the city by passing down the main valley. The present paper attempts to account for this directed dispersal in terms of the behaviour of Aedes mosquitos in response to certain physical factors in the environment. The species mainly concerned were Aedes cataphylla Dyar, A. fitchii (Felt & Young), A. excrucians (Wlk.) and A. stimulans (Wlk.).

The initiation of dispersal flight downwind across the plains at twilight was observed. This took place soon after emergence and was not prevented by moderate winds. It was shown experimentally that neither high wind speeds nor turbulence inhibited the flight of newly emerged Aedes mosquitos, but that individuals several days old were reluctant to take flight in turbulent conditions. Since wind speeds on the plains were generally higher than those in the valleys, these reactions would tend to confine older mosquitos to the valleys while not preventing dispersal of newly emerged mosquitos across the plains.

The direction of the initial dispersal flights from the breeding places was observed in mosquitos escaping from rearing cages. Take-off was characteristically into the wind, but re-orientation downwind took place when the mosquitos began to be blown backwards in flight. It was shown experimentally, by releasing mosquitos in the field when the wind was very light, that the preferred direction of flight uninfluenced by wind was towards the lowest part of the horizon, both on the plains and in the valley. This response would tend to cause mosquitos on the plain to fly into ravines and valleys, and thence down-stream within them. Dispersing mosquitos would thus tend to be held by any valleys or ravines in their path.

Swarming was never observed near the pools from which the mosquitos emerged, but was mainly seen in the valley or on the edge of the valley and ravines. Swarming of A. cataphylla took place during the evenings after the initial dispersal. The swarms were predominantly male but mating occurred during swarming. A cohesive factor seemed to be involved in the behaviour of the swarms, and further dispersal also seemed to occur gregariously; the movement of large male swarms down the river valley was observed.

By the application of optomotor theories of insect flight to previously published data on the flight speed and behaviour of A. aegypti (L.) and A. punctor (Kby.), the relationships between wind speed and permissible heights of flight of these species upwind and downwind were calculated. These relationships were consistent with the observations on dispersal of Aedes mosquitos in the Edmonton area, and could largely explain the mechanism by means of which deep valleys attracted and held dispersing mosquitos.

In contrast to the open plains, the wooded river valley provides a more favourable environment for adult mosquitos. The supply of nectar is greater, saturation deficiency and wind speeds are lower and less variable, and shaded resting sites are more abundant.

Observations on mosquitos in chambers with either vertical or horizontal humidity gradients suggested that the behaviour of Aedes mosquitos is not greatly influenced by humidity.

Two experiments on factors affecting the size and composition of catches of tsetse flies, principally Glossina pallidipes Aust., were carried out in 1963 in South Busoga, Uganda. Eight attractants were distributed between eight sites on eight successive days in a Latin square design for each experiment. The attractants comprised two black Zebu oxen and Morris traps covered with ordinary hessian (brown traps) or with hessian dyed black (black traps). Three of the sites were on the edge of a large thicket, two were close to isolated clumps of thicket in the midst of grassland and three were in the open grassland itself. Catching took place for 12 hours each day. The total numbers and sex ratio were recorded for each catch, and also, from dissections, the age composition and pregnancy states of the female portion of the catch. Examples of G. brevipalpis Newst., G. palpalis fuscipes Newst. and of 13 species of Tabanidae were also caught, but in smaller numbers, and were recorded in less detail.

Catches of G. pallidipes at sites close to the thicket edge were considerably greater than at sites away from the thicket, but, apart from an increased proportion of nulliparous females at the clump and grass sites, the composition of the female sample was unaffected by the type of site. The bait-oxen caught larger samples than the traps, but a smaller proportion of females, and these contained a higher proportion of young flies and of flies carrying an egg in the uterus. In comparison with brown traps, black traps caught smaller numbers of G. pallidipes, and a smaller portion of females, but a larger proportion of these were nulliparous. Although the two oxen had been selected for similarity of size and colour, they differed in the samples they attracted: one of them consistently attracted a larger sample of all the common species and, in the second experiment, a larger proportion of females in the samples of G. pallidipes. Most examples of G. palpalis fuscipes were caught at the three edge sites, and all but one example of G. brevipalpis were caught on the bait-oxen.

All examples of the 13 species of Tabanidae caught on the oxen or in the traps were females. Apart from Tabanus par Wlk. they were poorly represented in the trap-catches, and there was no obvious effect of site upon the size of the samples.

The effects of pockets of damp wheat upon the spatial structure (dispersion) of experimental populations of adults of Cryptolestes ferrugineus (Steph.) were investigated in the laboratory. Isolated pockets of non-mouldy wheat of 18 per cent, moisture content (85 per cent. R.H.) and of equally moist wheat supporting a mould flora (mainly Aspergillus candidus) were placed in a larger bulk of wheat of 14 per cent, moisture content (70 per cent. R.H.) at 25°C. One hundred beetles were released at the centre of the top surface of the bulk, and their dispersion within it was observed one week later. The method used allowed the entire bulk (25 kg.) to be quickly broken down so that the relative numbers of individuals in each of the 64 cubes of which it was composed could be recorded. Using other apparatus, the responses of single, isolated individuals to these physical conditions were analysed.

Insects reared at 25°C. and 70 per cent. R.H. accumulated to an equal extent in the pockets of damp wheat irrespective of whether it was mouldy or not. Insects in a preferendum arena went to the drier side, i.e., to 70 per cent, as opposed to 85 per cent. R.H., and the underlying mechanism was found to be a klinokinetic response to humidity. Maintaining insects at 40 or 85 per cent. R.H. for 14 days before testing did not alter their dispersion behaviour in bulks of grain; maintenance at 40 per cent. R.H. did not alter their response to humidity in a preferendum arena, but at 80 per cent. R.H. it was abolished.

A study of oviposition behaviour showed that when there was a choice between wheat of 18 and 14 per cent, moisture content, nearly all the eggs were laid in the damper grain, both when it was mouldy and when it was not. It is considered that oviposition requirements, and to some extent trophic behaviour patterns, over-ride the hygrokinetic response when wheat is damp or damaged, but that under field conditions, where the presence of dust and broken grain throughout the bulk provide conditions suited for oviposition and feeding, accumulations due solely to hygrokinesis may occur in the drier parts of a bulk.

The results are discussed in relation to the ecology of the species in grain and to its detection and control; and evidence from this and other studies is discussed in relation to the dynamic nature of spatial organisation of insect populations in grain.

The mode of inheritance of dieldrin-resistance in house-flies, Musca domestica L., was investigated by crossing experiments, using a selected, inbred resistant colony (R) and a normally susceptible one (N). Levels of susceptibility in both colonies and in various hybrids derived from them were determined by treating batches of flies with different concentrations of dieldrin by topical application.

Reciprocal crosses gave closely similar results, which were pooled. Results obtained with males and females were analogous, but were treated separately. The F1 hybrids were intermediate in resistance and the F2 generation segregated into susceptible, hybrid and resistant individuals in the ratio 1:2:1. The F1 generation back-crossed to either parental strain gave 1:1 segregation, corresponding to NN + NR or NR + RR. After killing the more dieldrin-susceptible forms in each case, the remaining males were back-crossed again. The second back-cross to normal gave a further 1:1 segregation of susceptibles and hybrids. The second back-cross to resistant now gave all homozygous resistant forms.

These results strongly indicate monofactorial inheritance.

Two highly dieldrin-resistant colonies of the sheep blowfly Lucilia cuprina (Wied.) had been colonised, one from Australia and one from South Africa. These were crossed and the progeny maintained to the F2 generation. Tests with dieldrin on the F1 and F2 generations gave results resembling those obtained with the parents. Since there was no appearance of susceptible or hybrid forms in the F2, it is concluded that the genes in the two colonies occur on the same chromosome and are either allelic (possibly identical) or very closely linked.

Populations of the leaf-miner Leucoptera meyricki Ghesq. and its parasites, of which Zagrammosoma variegatum (Masi), Achrysocharella ritchiei Ferriére and Parahormius leucopterae Nixon were the most abundant, were studied for 40 consecutive weeks during 1960–61 in Kenya, in four experimental blocks of coffee (Coffea arabica), two of which received several applications of parathion sprays and the other two none. Each week eight different trees within each block were covered with a tent, pyrethrum spray was atomised within, and the adult moths and parasites were recovered from the polyethylene sheeting used as a floor to the tent. Fortnightly, counts of leaves, mined and unmined, and collections of leaves with leaf-miner larvae and parasites within them were made. These intensive studies were supplemented with two special spray tests, in which different dosages of insecticides were used, and with collections of leaves made periodically over a rather extensive area in Kenya, from which adult leaf-miners and parasites were reared to gain information on the parasite/host relationships over a wide range of ecological conditions.

Parathion used at 1 lb. 20 per cent, wettable powder in either 65 or 80 gal. water per acre appeared to kill all adult leaf-miners and parasites present. Possibly between 50 and 75 per cent, of the leaf-miner larvae, and appreciably fewer of the immature stages of the parasites within the mines, were killed. The sprays apparently had even less effect on the leaf-miner prepupae and pupae and the parasites within the cocoons, which are usually formed in the litter and in crevices in the soil.

Leaf-miner populations within the sprayed blocks were somewhat lower than those in the unsprayed blocks, but the fluctuations were remarkably similar. In general, this was also true for the parasites.

Assessment of the effects of the sprays on the efficiency of the parasites was made on the basis of the ratios of adult parasites to moths obtained from tented trees and from infested leaf samples held for adult emergence, as well as in terms of percentages of larvae parasitised in the samples dissected. It was found that the sprays killed a greater proportion of the leaf-miner larvae than of parasites within the mines, and thus increased the ratios of living parasites to leaf-miners immediately following the spray applications. During the period from October to January, when the sprays in the Eukera plots were synchronised with the peak populations of the moth, parasitisation was significantly higher in the sprayed plots than in the unsprayed plots. Furthermore, in the special spray tests, where different dosages of parathion and diazinon were used, parasitisation within the surviving populations was higher in the plots that received the higher dosages. These findings suggest that with proper timing of spray applications the efficiency of leaf-miner parasites may be improved.

The number of eggs produced by females of Anobium punctatum (Deg.) (Col., Anobiidae) was determined at Auckland, New Zealand, during annual emergence in December 1957. The females were collected before mating and egg-laying occurred. Each female was weighed and then confined, with males, to an egg-laying block of sapwood of Podocarpus dacrydioides. The average number of eggs per female was 54·8, far higher than obtained from field-collected females, and additionally the egg-laying distribution was neither skewed nor censored. Following a short preoviposition period, eggs were laid rapidly, egg-laying being virtually finished by the 15th day after emergence. Females lived a few days after egg-laying had ceased, maximum length of life being between 24 and 31 days.

For about 60 per cent, of females the number of eggs laid was closely related to the initial weight of the female, but the remaining females laid fewer eggs in relation to their weight.

The extent of the dependence of the foreign grain beetle, Ahasverus advena (Waltl), upon moulds in its diet was investigated.

Using a simple technique, the insect was cultured axenically at controlled temperature and relative humidity on an autoclaved mixture of rolled oats, wheatfeed and dried yeast. After the mixture was sterilised by exposure to propylene oxide vapour, virtually no larvae completed development on it in the absence of living micro-organisms, and this effect was unchanged by the addition of a mixture of B-vitamins followed by autoclaving. However, when fungi were grown on the food previously sterilised with propylene oxide, it again permitted the complete development of the insect.

Autoelaved wheat germ was not a suitable diet for A. advena unless a small proportion of dried yeast was added before autoclaving. It is concluded that living fungi are not essential in the diet of the insect, but that they may supplement an otherwise inadequate diet.

The minimum development time from egg to adult on a complete food at 80 per cent. E.H. and 30°C. varied from 18 to 25 days.

The mode of inheritance of dieldrin-resistance in Cimex lectularius L. and Pediculus h. humanus L. was investigated. The method involved the determination of dosage/mortality regression lines by exposing batches of insects to a range of dieldrin concentrations. Reciprocal crosses were made between normal (N) and resistant (R) strains of each insect, and the F1 and F2 progeny were examined for susceptibility levels over a wide range of concentrations of dieldrin. Back-crosses were made from the F1 generation to N and R strains, and the progeny were examined in the same way. In some cases, further back-crosses were made after elimination of susceptible individuals from the progeny of the first back-cross.

All the results with C. lectularius were consistent with monofactorial inheritance of dieldrin-resistance through a gene of intermediate dominance. With P. h. humanus, the results were complicated by an apparent maternal effect which caused the F1 and F2 generations from a N ♀ × R ♂ cross to be less resistant than those from a R ♀ × N ♂ cross. In general, however, the results indicated genetic segregation consistent with the same type of monofactorial inheritance as that found in C. lectularius.

The egg production and development of Trogoderma anthrenoides (Sharp) has been studied over a range of temperatures from 17·5 to 37·5°C. and in relative humidities of 70 per cent, and near 0 per cent.

At 70 per cent. R.H., the minimal temperature for development was between 17·5 and 20°C. and the maximum between 35 and 37·5°C. Adult females, which apparently required no food, lived on average 18 days at 37·5°C., this period increasing with falling temperature to 146 days at 17·5°C. The greatest number of eggs, a mean of 54 per female present, were laid at 27·5°C. The quickest development occurred at 35°C., females taking a mean of 44.7 days (egg 6; larva 34·3; pupa 4·4). Male larvae developed slightly faster and male adults died a little earlier than females.

Near-zero humidity shortened adult life, reduced egg production and prevented the development of larvae.

Some larvae entered a condition that is probably a facultative diapause resembling that of T. parabile Beal. The diapause was terminated by an increase in volume of food combined with a change of temperature.

The biology of T. anthrcnoides resembles that of two minor pests, T. parabile and T. inclusum Lee., more than that of the important pest T. granarium Everts. The first two species show no signs of becoming serious pests. It is concluded that T. anthrcnoides probably has the potential only of a minor pest.

Detailed studies are described, and illustrated by photomicrographs, of the method by which the newly emerged pupae of Mansonia annulifera (Theo.) and M. uniformis (Theo.), which are important vectors of filariasis in Kerala State, India, attach themselves to the aquatic plant Pistia stratiotes. After emergence of the cephalothorax through the ruptured larval skin, the latter continues to support the pupal abdomen while this doubles over so that the respiratory trumpets of the cephalothorax are directed towards and eventually reach the point of insertion of the larval siphon into the Pistia root. The trumpets are then plunged into the hole occupied by the larval siphon, which is almost simultaneously yanked out of it by the straightening of the pupal abdomen, leaving the pupa attached by its trumpets. The pupa casts off the larval skin posteriorly and then curls round to assume the usual comma shape. The entire process occupies under one minute in M. annulifera and 3–6 minutes in M. uniformis.

Adults of Zonocerus variegatus (L.) collected in southern Nigeria in January to May 1963 were found to be parasitised by larvae of Blaesoxipha filipjevi Rohd. Of 1,691 adults of Z. variegatus dissected, 43 contained from one to six larvae of B. filipjevi, but none was found in 167 nymphs dissected mostly in January and February. No parasites were found in 155 examples of 11 other locally occurring species of Orthoptera. Full-grown larva left their hosts through the cervical membrane; they pupated within 48 hours, probably in the soil in natural conditions, and the adult Sarcophagid emerged 9–10 days later. No larva was observed to undergo diapause. The presence of the parasite restricted the ovarian development of the female host, but the species is considered to be of negligible importance in the control of Z. variegatus because of its low incidence.

Oviposition and the length of adult life in the Bruchid beetle Caryedon gonagra (F.), an important pest of unshelled groundnuts (Arachis) in West Africa, were studied in continuous darkness in incubators at 30 and 40°C. at relative humidities of 50, 70 and 90 per cent., and at 45°C. and 70 per cent., and also under conditions of diurnal alternation of periods of light and darkness in a constant-temperature room at about 27·5°C. and 75 per cent. R.H. Newly emerged beetles were placed, singly (unmated or after a single mating) or in pairs, in tubes with 1–5 unshelled groundnuts. In addition, the influence of the absence of groundnuts was investigated.

Length of life of the adults increased with decreasing temperature, increasing relative humidity, the absence of nuts (for females only) and the absence of mating (for females, and, in absence of nuts, for males). Adults survived for 3–4 days at 45°C. and 70 per cent. R.H. Optimum conditions are probably about 27·5—30°C. and 70—90 per cent. R.H., under which the adult length of life was about 21 days.

The adults were sexually mature on emergence from the cocoons, and mating took place within 24 hours of emergence. Under the conditions of the experiments, the preoviposition period was between 24 and 48 hours. At 27·5 and 30°C., the mean length of the oviposition period (9—13 days) was only slightly influenced by relative humidity, being slightly shorter at the lowest R.H. (50%); an increase in temperature from 30 to 40°C. caused a marked reduction in the period.

About 80 per cent, of the eggs were laid in crevices in the shell of the nut, where they are difficult to find. In the absence of nuts, the females laid readily between the cork and the glass and at the bottom of the tube.

At 40°C., oviposition was inhibited at 50 and 70 per cent. R.H., but at 90 per cent. R.H. many eggs (but significantly fewer than at lower temperatures) were laid; the largest mean numbers (106–115) were laid at 27·5–30°C. and 70–90 per cent. R.H.; absence of nuts did not influence the numbers of eggs laid, but caused some irregularity in the oviposition pattern. More than one copulation appeared to be necessary for the female to lay a full complement of eggs.

Under conditions of alternating periods of light and darkness, there was a daily rhythm of oviposition, with a strong correlation between numbers of eggs laid and the periods of darkness.

The results are compared with those recorded in the literature.

The cross-resistance characteristics of a dieldrin-resistant strain of Aedes aegypti (L.) from Puerto Rico were investigated by comparative tests on the adults of this and of a normal strain, using various insecticides. A resistance spectrum typical of that associated with resistance to BHC/dieldrin in other insects was revealed, characterised by slight or negligible cross-resistance to DDT, malathion and diazinon.

The mode of inheritance of dieldrin-resistance was studied by determining resistance levels in the progeny of direct crosses of the resistant and normal strains and of back-crosses. The F1 generation of the direct cross was of intermediate resistance, and the F1 generation showed 1:2:1 segregation into normal, intermediate and resistant individuals. Both back-crosses showed 1:1 segregation into susceptible and intermediate individuals when the back-cross was to the susceptible parent, or into intermediate and resistant individuals when it was to the resistant parent, and these results were confirmed when one genotype was eliminated and the back-cross was repeated. These results indicate monofactorial inheritance of an autosomal gene with intermediate dominance, which is typical of the BHC/dieldrin type of resistance.

The effect upon the three-dimensional dispersion of experimental populations of Tribolium castaneum (Hbst.) of internal pockets of grain at 18 per cent, moisture content, either mouldy or free from mould, and superficial ones of 25 per cent, moisture content, in a larger bulk of 14 per cent, moisture content, was investigated at 25°C. The behaviour under these circumstances of insects reared and maintained at 70 per cent, relative humidity was compared with those conditioned at 40 per cent. R.H. for 14 days. It was found that insects reared at 70 per cent. E.H. did not accumulate in the damp grain whereas conditioned ones did. The underlying response was shown to be hygrokinetic and the mechanism an orthokinetic one. The rate of movement of unconditioned adults in grain of 18 per cent, moisture content was approximately twice that in grain of 14 per cent, moisture content. Conditioned adults moved very slowly in the damper grain. There were no significant variations in irregularity of pathway (klinokinesis) under any of these circumstances. When grain of 18 per cent, moisture content supporting a mould growth was used, unconditioned adults did, however, accumulate in it due to trophic behaviour.

While there is considerable plasticity of behaviour in this species a synthesis is attempted of the causal behavioural mechanisms underlying the spatial structure of populations in ecological situations involving humidity gradients; the results are also discussed in relation to grain storage conditions, and the detection and control of the species.

Two types of population history shown by Lasioderma serricorne (F.) are described, one when the food was renewed at regular intervals, the other when there was no food renewal. Initially, both of these populations increased together to a high level, the former continuing at this level until the observations were discontinued, the latter declining and eventually becoming extinct. Stage-specific properties, which relate the numbers in each stage to those a unit of time previously and which are functions of the survival, developmental and fecundity rates, were estimated for each type of population; they are compared as between the two types and with the corresponding properties of a population given effectively unlimited space and food. It is shown that the effect of the limiting conditions produced a decrease in survival, developmental and fecundity rates. From this, together with other evidence, it appears that food shortage, not space shortage, was the primary cause. After the initial increase in numbers, the stage-specific properties shown by the species in both populations imply that there was a regular oscillation in the developmental, survival or fecundity rates, which would result in corresponding fluctuations in numbers.