Nesting Phenology and Clutch Characteristics of Captive Siamese Crocodiles (Crocodylus siamensis) in Cambodia

The Siamese crocodile (Crocodylus siamensis) is considered one of the least studied and most critically endangered crocodilians in the world. Although few wild populations remain, more than 700,000 C. siamensis are held on commercial crocodile farms in Southeast Asia. Despite conservation concerns, many aspects of C. siamensis life history remain poorly known, particularly with regards to its reproductive biology. We studied nesting phenology, clutch characteristics, and other aspects of C. siamensis reproductive biology on crocodile farms in Cambodia during 2000 and 2001. Oviposition among captive crocodiles began in February and continued into early June. The mean (±1 SD) oviposition date based on pooled data from 2000 and 2001 was 5 April ± 24 days. Mean oviposition date differed significantly between 2000 and 2001, possibly as a result of annual variability among nesting cues. The mean incubation period was 72 ± 3 days and eggs hatched from 5 May to 18 August. Mean clutch size (25.0 ± 8.8 eggs; n = 183) differed significantly between years, possibly resulting from the >2.5‐fold increase in sample size during 2001. There was no correlation between clutch size and oviposition date during either 2000 or 2001. A single female produced two clutches during 2001, complimenting previous reports of double‐clutching among C. siamensis. The mean length and width of 515 eggs were 78.2 ± 4.9 and 48.1 ± 2.5 mm, respectively; mean egg mass was 90.8 ± 16.5 g (n = 471). One unpipped egg contained a set of twins. Zoo Biol 31:534‐545, 2012. © 2011 Wiley Periodicals, Inc.     

Behavioural and body mass changes before egg laying in the Barn Owl: cues for clutch size determination?

To investigate laying decision and clutch size determination in indeterminate layers, we analysed in-nest activity (nest presence, and copulation, prey deliveries, and entrance frequencies) and female body mass change, as well as their relation to clutch size variation in five Barn Owl pairs (Tyto alba) nesting in eastern France. Body mass of the female and behaviour [copulation frequency, entrance frequency, and prey delivery to the nest by the male (in number and mass)] were monitored using an automated weighing system and a video camera. There was a consistent change of behaviour and foraging activity among pairs ca. 18 days before laying indicating that the females may be tied to the nest at this time. Barn Owls being indeterminate layers have their clutch size determined at the oviposition of the first egg of the clutch. Window correlation analyses between the clutch size and the female body mass gain indicate that the clutch size might be determined no later than a few days before the laying of the first egg. Our results suggest that female Barn Owls may use the pre-laying period to determine the clutch size using cues such as the male food deliveries (a proxy for male quality).     

Oviposition behavior and progeny allocation of the polyembryonic waspCopidosoma floridanum (Hymenoptera: Encyrtidae)

Oviposition behavior was used to determine the primary clutch size and sex ratio of the polyembryonic wasp Copidosoma floridanumAshmead (Hymenoptera: Encyrtidae) parasitizing Pseudoplusia includens(Walker) (Lepidoptera: Noctuidae). The laying of a female egg was associated with a pause in abdominal contractions during oviposition, while the laying of a male egg was associated with uninterrupted abdominal contractions. Although unmated females produced only male broods, they also displayed male and female egg oviposition movements. Wasps always laid a primary clutch of one or two eggs. For mated females if only one egg was laid, the emerging secondary clutch was all male or female, but if two eggs were laid a mixed brood of males and females was almost always produced. The secondary clutch of single sex broods was usually between 1000 and 1200 individuals, but the secondary clutch of mixed broods averaged 1143 females and 49 males. Thus, the primary sex ratio for mixed broods was 0.5 (frequency males), but the secondary sex ratio was 0.042. Manipulation of the sequence of male and female egg oviposition or of the primary clutch did not produce major alterations in the secondary clutch size or sex ratio.     

Geographical variation in reproductive traits and trade‐offs between size and number of eggs in the king ratsnake,Elaphe carinata

We collected gravid king ratsnakes (Elaphe carinata) from three geographically separated populations in Chenzhou (CZ), Lishui (LS) and Dinghai (DH) of China to study the geographical variation in female reproductive traits and trade‐offs between the size and number of eggs. Not all reproductive traits varied among the three populations. Of the traits examined, five (egg‐laying date, post‐oviposition body mass, clutch size, egg mass and egg width) differed among the three populations. The egg‐laying date, ranging from late June to early August, varied among populations in a geographically continuous trend, with females at the most northern latitude (DH) laying eggs latest, and females at the most southern latitude (CZ) laying eggs earliest. Such a trend was less evident or even absent in the other traits that differed among the three populations. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar to each other in most traits examined. LS females were distinguished from CZ and DH females by the fact that they laid a greater number of eggs, but these were smaller. The egg size–number trade‐off was evident in each of the three populations and, at a given level of relative fecundity, egg mass was significantly greater in the DH population than in the LS population. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 701–709.     

The use of ultrasonography to assess reproductive investment and output in pythons

Reproductive investment and output are integral fitness components, often incorporated into life‐history trade‐off models and important to population dynamics. The trade‐offs associated with reproduction can be dramatic in species such as snakes that make especially large investments into reproduction. Unfortunately, traditional methods used to determine reproductive investment and output are effective in many (but not all) situations. Thus, we used portable ultrasonography to serially estimate reproductive investment and reproductive output in three python species that exhibit significant variation in phylogeny, geographic range, body size, egg size, and clutch size: ball pythons (Python regius), Children's pythons (Antaresia childreni), and water pythons (Liasis fuscus). At each time point of measurement (range: 1–49 days pre‐oviposition), ultrasound estimates of viable clutch size were highly accurate in all three species. However, ultrasound estimates of mean viable egg mass, and thus viable clutch mass, significantly differed from the actual values (range: 23–73% error). Interestingly, this error was considerably smaller as females approached oviposition, suggesting that female pythons transfer a significant amount of water into their eggs during the week before oviposition. Thus, water balance during late‐stage egg development may be an integral part of reproductive success. The results obtained in the present study form the foundation for future assessments of reproductive investment, and also provide insight into the use of ultrasound technology to assist such efforts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 772–778.     

Effects of spatial autocorrelation,natal philopatry and phenotypic plasticity on the heritability of laying date

We investigated the effect of spatial autocorrelation on heritability (h²) estimates of laying date and clutch size in a population of great tits Parus major. We found that h² of laying date, but not clutch size, declined significantly with increasing distance between the nestbox of mothers and daughters. This decline was caused by a decreasing effect of spatial autocorrelation in laying date, rather than by the existence of genotype–environment interactions (GEI). After correcting for the effect of spatial autocorrelation, h² of laying date was low (0.16 ± 0.07), but significant, and surprisingly consistent with increasing distance between parental and offspring environments. The h² of clutch size was not much affected by spatial autocorrelation. Most previously published estimates of the heritability of laying date include various degrees of common environment effects, which can bias estimates both upwards and downwards. We suggest that using techniques that take spatial autocorrelation into account might be a fruitful approach to estimate h² of traits that show a high degree of plasticity.     

Effects of intraclutch variation in egg size and hatching asynchrony on nestling development and survival in semi‐precocial Herring Gulls

Intraclutch egg size variation may non‐adaptively result from nutritional/energetic constraints acting on laying females or may reflect adaptive differential investment in offspring in relation to laying/hatching order. This variation may contribute to size hierarchies among siblings already established due to hatching asynchrony, and resultant competitive asymmetries often lead to starvation of the weakest nestling within a brood. The costs in terms of chick mortality can be high. However, the extent to which this mortality is egg size‐mediated remains unclear, especially in relation to hatching asynchrony which may operate concomitantly. I assessed effects of egg size and hatching asynchrony on nestling development and survival of Herring Gulls (Larus argentatus), where the smaller size and later hatching of c‐eggs may represent a brood‐reduction strategy. To analyze variation in egg size, I recorded the laying order and laying date of 870 eggs in 290 three‐egg clutches over a 3‐yr period (2010–2012). I measured hatchlings and monitored growth and survival of 130 chicks from enclosed nests in 2011 and 2012. The negative effect of laying date (β = ?0.18 ± SE 0.06, P = 0.002) on c‐egg size possibly reflected the fact that late breeders were either low quality or inexperienced females. The mass, size, and condition of hatchling Herring Gulls were positively related to egg size (all P < 0.0001). C‐chicks suffered from increased mortality risk during the first 12 d, identified as the brood‐reduction period in my study population. Although intraclutch variation in egg size was not directly related to patterns of chick mortality, I found that smaller relative egg size interactively increased differences in relative body condition of nestlings, primarily brought about by the degree of hatching asynchrony during this brood‐reduction period. Thus, the value of relatively small c‐eggs in Herring Gulls may lie in reinforcing brood reduction through effects on nestling body condition. A reproductive strategy Herring Gulls might have adopted to maintain a three‐egg clutch, but that also enables them to adjust the number of chicks they rear relative to the prevailing environmental conditions and to their own condition during the nestling stage.     

Maturation increases early reproductive investment in Adélie Penguins Pygoscelis adeliae

Correlations between female investment in egg production and age, breeding experience and laying date have been reported in several seabird species. In general, clutch and egg sizes increase with female age and breeding experience but decrease with laying date. Positive correlations of clutch and egg size with age and breeding experience can be caused by an increase in reproductive investment with maturation or they may be an artefact of lower survival rates for individuals with poor-quality phenotypes. Negative correlations of clutch and egg size with laying date might signal an adaptive reduction in egg production or be due in part to variation among individuals. We examined the interactions of female age, breeding experience, laying date and clutch and egg size in Adélie Penguins Pygoscelis adeliae . Breeding experience strongly affected clutch size with 87.3% of all one-egg clutches laid by first-time breeders. In addition, increasing age had a positive influence on egg size and was associated with earlier laying dates. However, there was little evidence to suggest that either clutch or egg sizes are influenced by laying date. Laying dates and clutch and egg sizes did not affect a female's probability of returning to breed in the following year, indicating that increased investment is a product of maturation and not of the loss of poor-quality breeders from the population. Our results suggest that as female Adélie Penguins gain foraging and breeding experience they are able to initiate breeding earlier, to lay complete clutches of two eggs and to lay larger eggs.     

Determining Great Bittern Botaurus stellaris laying date from egg and chick biometrics

Capsule Great Bittern breeding phenology can be estimated from egg and chick biometrics.

Aims To estimate egg or chick ages in order to back-calculate egg-laying dates.

Methods Bittern nests were searched for in six French and three Belarussian sites between 1999 and 2004. Eggs and chicks were measured at each visit. By using a subsample of nests with known egg-laying (or hatching) dates, regression equations are determined using egg density and tarsus length in order to estimate, respectively, egg and chick ages. Additionally in Belarus, the ‘water test’ was used to estimate the incubation stage of the clutch.

Results A total of 141 Bittern nests were found. Egg density decreased linearly from 1.063 at laying to 0.915 the day before hatching. A regression equation therefore allows estimation of egg age from its density. A scale was also constructed to estimate egg age from its position in water, and the accuracy of the two methods is compared. Chick growth rates were similar between the two countries. Before the age of 25 days, chicks are best aged by tarsus length compared to other measurements (weight, bill length). No data were available after that age because chicks were no longer found on nests.

Conclusions Egg-laying date can be estimated to within ±3 days using egg density, and to within ±5 days, using the ‘water test’. Tarsus length can be used until the age of 25 days to age chicks to within ±2 days. These simple measurements provide efficient and accurate methods to record the breeding calendar of this endangered species.     

Breeding ecology of Red‐faced Cormorants in the Pribilof Islands,Alaska

ABSTRACT Red‐faced Cormorants (Phalacrocorax urile) are North Pacific endemics recognized as a vulnerable species, but little is known about their breeding ecology. We studied Red‐faced Cormorants on St. Paul Island, Alaska, from 1975 to 2009, with more detailed data collected in 2004 and 2005. Mean clutch sizes in 2004 (3.2 ± 0.8 [SD] eggs) and 2005 (3.1 ± 0.8 eggs) were similar to the long‐term average (2.9 ± 0.3 eggs from 1976 to 2009). The mean laying interval in 2004 and 2005 was 2.15 ± 0.80 d (N= 407), and the mean egg period (number of days between laying of an egg and hatching) was 31.1 ± 1.4 d (N= 158). Approximately 64 ± 17% of eggs hatched during the period from 1975 to 2009. The mean number of chicks per nest in 2004 and 2005 was 2.8 ± 0.8 (N= 232), and the mean number of fledglings per initiated nest in all years was 1.22 ± 0.52. Chicks fledged 46 to 66 d posthatching. In 2004 and 2005, the primary causes of egg loss were predation by Arctic foxes (Vulpes lagopus) and destruction of eggs and abandonment of nests due to storms. Starvation was the primary cause of nestling mortality in both years. Because chicks are dependent on parents to provide food for over 45 d, consistent near‐shore foraging opportunities must be available. From 1975 to 2009, Red‐faced Cormorants experienced only 1 yr of complete reproductive failure (1984). The consistent reproductive success of Red‐faced Cormorants suggests that conditions may be relatively stable for this species on St. Paul Island, or that the variability in their breeding ecology (e.g., phenology, clutch sizes, and incubation strategies) provides the flexibility needed to successfully fledge some chicks nearly every year.     

Testing the relationship between clutch size and brood size in the Coot (Fulica atra)

The time between egg laying and chick fledging is of crucial importance for the survival of young birds. I analyzed breeding output at consecutive phases of growth of young Coots (Fulica atra) relative to the clutch size and laying date. Considering the specific breeding biology of the Coot, I tested whether chick survival reveals clutch size-dependent variability. Clutch size did not affect hatching success; it only affected brood size, and that merely temporarily. During the first 20 days after hatching, i.e. during the time of the highest chick mortality, birds with larger clutches lost chicks at a higher rate. As a result, the number of fledged chicks was independent of the initial number of chicks, and pairs with different clutch sizes had a similar number of fledglings. The laying date had no effect. This pattern of age-related chick survival points to the greater role of the type of chick growth (semi-precocial) and behavior in their survival.     

Experimentally induced clutch size enlargements affect reproductive success in the Pied Flycatcher

We performed a food provisioning experiment in a population of Pied Flycatchers Ficedula hypoleuca breeding at high altitude in central Spain to test if food availability before and during laying determines clutch size. Food was provided to one of two pairs with the same date of initiation of nest-building (15 dyads of subsequently reproducing pairs were thus created). Food provisioning began on the day of initiation of nest-building and ended on the day after the last egg was laid. Although laying date was unaffected by the experiment, clutch size in the experimental treatment was significantly larger. This result could indicate that food availability at laying (1) proximately constrained clutch size or (2) that females evaluated future conditions for incubating eggs and feeding nestlings based on food availability at laying. Reproductive success (proportion of eggs that resulted in fledged young) was significantly reduced in the experimental treatment. This effect suggest that supplemented females were tricked by the experiment into laying more eggs than the number of eggs they were able to incubate with success and the number of nestlings they were able to feed, a source of error in clutch size adjustment which could be common in non-experimental situations.     

<Emphasis Type="Italic">Fopius arisanus</Emphasis> oviposition in four <Emphasis Type="Italic">Anastrepha</Emphasis> fruit fly species of economic importance in Mexico

We studied the oviposition performance of Fopius arisanus (Sonan) (Hymenoptera: Braconidae) attacking eggs of four fruit flies of the genus Anastrepha Schiner (Diptera: Tephritidae) under laboratory conditions. The complete process of oviposition on an individual egg of Anastrepha ludens (Loew) lasts in average 85.4 ± 2.9 s, including a tremor (25.8 ± 1.03 s) observed in the middle of this process related to the egg’s descent. The average parasitism of A. ludens egg was 60.9 ± 7.5%, with only 1.2% of superparasitized eggs. During individual acts of oviposition, we noted that F. arisanus possesses a highly flexible ovipositor that curves easily as it searches for additional suitable eggs, which may be of particular benefit when a female finds large clutches of eggs. The individual oviposition of F. arisanus in host fruits attacked by Anastrepha spp. varies with the egg clutch size of each fruit fly species: A. serpentina laid the biggest egg clutches (21.3 ± 1.4), followed by A. ludens (14.2 ± 0.9), and A. striata (1.0 ± 0.0) (=A. obliqua). The time spent by F. arisanus in individual ovipositions was parallel to these findings, reinforcing the idea that F. arisanus attacks several eggs in each individual insertion of its ovipositor. Neither formal oviposition acts, nor adult emergences of F. arisanus were registered in A. obliqua. We discuss the potential of F. arisanus as natural enemy of fruit flies of the genus Anastrepha, and explore the eventual developing of its mass rearing. Handling Editor: Torsten Meiners.     

Harem size and oviposition behaviour in a polygynous bark beetle

Abstract. 1. Harem polygyny can have fitness benefits and costs on females. In bark beetles of the genus Ips the latter may include within‐harem competition between larvae. However, earlier competition between females for male care and mating opportunities may also influence oviposition behaviour. There has been relatively little investigation into the relationship between harem size and initial egg output. The present study investigated this relationship in the bark beetle Ips grandicollis. 2. The measure of egg output used was the number of eggs in the gallery with the most eggs in each harem. Mean (±SE) harem size of 242 observed harems was 3.25 ± 0.10. A curvilinear relationship was found between egg output and harem size, with females in smaller harems (one to four females) laying more eggs with increased harem size. However, females in larger harems (five to seven females) laid fewer eggs as harem size increased. The optimal harem size (in terms of number of eggs laid) was close to four females. 3. We found no evidence from a behavioural assay that females could preferentially choose unmated males over mated males with harems of two females. Additionally, the distribution of harem sizes suggests that females distribute themselves among males randomly. 4. The results suggest that harem size has effects on female reproduction that extend beyond larval competition and influence patterns of oviposition. The mechanism that determines why egg laying is greatest at intermediate levels is unknown. There is no evidence that smaller harems belong to lower quality males, but females may adjust egg‐laying behaviour in large harems as a result of reduced male attendance or anticipated larval competition.     

A model of clutch size determination in birds

Summary This paper tests the hypothesis that the timing and the size of bird clutches are determined by (1) a tendency to delay reproduction so that the female can store enough internal resources for laying a large clutch; (2) a tendency to breed early because survival of offspring late in the breeding season might be lower than early. These factors are approximated by linear functions in a model. The model predicts that there will be a correlation between early breeding females and those that have large clutches. This agrees with published data for several bird species. Predictions from the model are also made of clutch size and the impact on final clutch-size if one egg is removed or added during the laying. These predictions were compared with data from a crow (Corvus cornix) population and were supported if it is assumed that the formation of an egg is a relatively costly process. More precisely, the model is supported if the formation of an extra egg requires a delay of about four or five days before laying can begin.     

Geographic variation in reproductive traits and trade-offs between size and number of eggs of the Chinese cobra (Naja atra)

We collected gravid Chinese cobras (Naja atra) from one island (Dinghai) and three mainland (Yiwu, Lishui and Quanzhou) populations in south‐eastern China to study geographical variation in female reproductive traits and the trade‐off between the size and number of eggs. We then conducted an common experiment on cobras from two of the four populations to further identify factors contributing to the observed trade‐offs. The mean size (snout–vent length) of the smallest five reproductive females increased with increasing latitude. Oviposition occurred between late June and early August, with females from the warmer localities laying eggs earlier than those from the colder localities. Maternal size was a major determinant of the reproductive investment in all populations, with larger females producing not only more but also larger eggs. Clutch size was more variable than egg size within and among populations. The observed geographical variation in clutch size, egg size, clutch mass and post‐oviposition body condition was not a simple consequence of variation in maternal size among populations, because interpopulation differences in these traits were still evident when the influence of maternal size was removed. The upper limit to reproductive investment was more likely to be set by the space availability in the island population, but by the resource availability in the three mainland populations. Trade‐offs between size and number of eggs were detected in all populations, with females that had larger clutches for their size having smaller eggs. Egg size at any given level of relative fecundity differed among populations, primarily because of interpopulation differences in the resource availability rather than the space availability. Except for the timing date of oviposition and the mean size of the smallest five reproductive females, all other examined traits did not vary in a geographically continuous trend. The common garden experiment, which standardized environmental factors, synchronized the timing date of oviposition, but it did not modify the conclusion drawn from the gravid females collected from the field. The observed geographical variation in the female reproductive traits could be attributed to the consequence of the effects of either proximate or ultimate factors. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 27–40.     

吉林白城地区草原栗斑腹(巫鸟)窝卵数、营巢成功率和繁殖成功率的研究

对分布于吉林白城地区草原生境中栗斑腹巫鸟的窝卵数、营巢成功率和繁殖成功率的初步研究结果表明 ,繁殖期栗斑腹巫鸟种群的平均窝卵数为 5 .0 9± 0 .5 8枚 /巢 ;窝卵数与产卵期、出巢数与产卵期、窝卵数与卵大小之间呈负相关 ,产卵期与孵化率之间存在极显著的负相关关系 ,巢外径与窝卵数之间存在显著的正相关关系 ,巢的其余指标均与窝卵数呈正相关 ;平均孵化期为 12± 0 .4 9d ,孵化率为 36 .3% ,繁殖成功率为 11.11% ;7日龄以上的雏鸟群体大小为 2 .5 6± 1.5 3只 ,栗斑腹巫鸟的雏鸟存活率为 2 7.6 9% .     

Western corn rootworm (Diabrotica virgifera virgifera LeConte) (Coleoptera: Chrysomelidae) oviposition can be released by decapitation

Nervous system control of western corn rootworm (Diabrotica virgifera virgifera LeConte, WCR) (Coleoptera: Chrysomelidae) oviposition was studied using decapitation. Gravid females (n = 364) were decapitated with scissors and floated in water-filled Petri dishes. Oviposition by individuals was observed at 30 min intervals for 4 hr after decapitation; cumulative oviposition was tallied at 48 hr post-treatment. Overall, 82.7% of females laid eggs within 48 hr. Oviposition commenced quickly; 78.4% of females laid eggs during the observation period, 81.8% of these began egg laying within 30 min of decapitation. Egg-laying females deposited a total of 66.8 ± 2.1 eggs (mean ± SEM); this was 85.1% of the total mature egg load. Dissection revealed that 31.9% of n = 301 laying females and 14.3% of 63 non-laying females had a rupture of the common oviduct, manifest as an egg-filled hernia containing a mean of 8.17 ± 1.3 eggs (range: 1–83). Among n = 237 females that laid eggs during observations, females with hernias laid significantly fewer eggs (35.8 ± 4.2) than intact females (48.0 ± 2.7) during the 4-hr interval. There was no difference in the mean proportion of hatch for eggs collected from the same n = 10 females before (0.88 ± 0.03) or after decapitation (0.84 ± 0.04). Rapid oviposition following decapitation suggests that WCR egg laying is under constant descending neural inhibition; the motor programme controlling egg laying must reside posterior to the head. Decapitation can be used to quickly collect mature, fertilized WCR eggs.     

Population Irruptions of Northern Bobwhite: Testing an Age-Specific Reproduction Hypothesis

Abstract: Age-specific reproduction has been suggested for northern bobwhite (Colinus virginianus) and has been hypothesized as a factor contributing to population irruptions. However, little research has been conducted on the subject. We conducted a laboratory and field study to determine if age-specific reproduction occurred in northern bobwhites. Our objectives were to compare 7 reproductive measures (% F nesting, date of first incubated nest, egg-laying rate, nesting rate, clutch size, egg mass, and egg hatchability) between first- and second-year breeders and determine if differential reproduction was impacted by diet quality. The laboratory study consisted of a 2 × 2 factorial experiment with age and diet quality (low protein [12%] and high protein [24%]) as the factors. Data for the field study represented a 6-year data set of bobwhite reproduction (May-Sep 2000-2005) obtained from an ongoing radiotelemetry study in southern Texas, USA. We documented similar productivity (i.e., % F laying, egg-laying rate, and egg mass) and timing of laying (i.e., date of first egg) between juvenile (n = 33) and adult bobwhites (n = 27) in our laboratory study. However, females on the high-protein diet exhibited a greater egg-laying rate than females on the low-protein diet. Under field conditions, we also documented no difference in productivity (% F nesting, nesting rate, clutch size, egg hatchability) and timing of nesting (date of first incubated nest) between age classes (n = 59 juv and 32 ad). Our findings do not support early suppositions of age-specific reproduction in quail. Quail irruptions should not be influenced by population age structure as it relates to age-specific reproduction.     

Effect of laboratory culture conditions on population growth of Proisotoma minuta (Tullberg) (Collembola: Isotomidae)

The collembolan Proisotoma minuta (Tullberg) was successfully maintained in a laboratory culture that could be used to produce large numbers of P. minuta of standard size and physiological condition. The general life history of P. minuta was studied using a substrate comprising a mixture of plaster of Paris and charcoal with baker's yeast as food. The mean time taken for eggs to hatch following oviposition was 10.6 ± 1.3 days at 17.5°C and 6 ± 0.5 days at 23°C. Conditions in the culture were very important for the production of large insect populations. Growth of the cultures was limited by the increasing population size and was probably affected by contamination of the habitat by the deposition of excretory materials. Proisotoma minuta from a population that had ceased egg production started oviposition after individuals were transferred to a fresh plaster of Paris and charcoal habitat.