Egg Cannibalism Research Articles

Ovoviviparity in Macrocheles glaber (Müller) (Acari: Macrochelidae), with notes on parental care and egg cannibalism

In Macrocheles glaber (Müller), oviposition can involve either oviparity or egg production followed by immediate hatching of the larva, a process that may be called ovoviviparity. We observed three phases in the process of ovoviviparity: preoviposition behaviour, oviposition followed by holding the egg under the gnathosoma and hatching of the larva assisted by the female. Two factors appear to favour the occurrence of ovoviviparity in this species: poor feeding and poor substrate quality. We witnessed egg cannibalism four times in two of the four females that we observed. We discuss the consequences of variable oviposition strategy, parental care and egg cannibalism in M. glaber in the context of maximization of reproductive success.

Ant larvae as players in social conflict: relatedness and individual identity mediate cannibalism intensity.

Conflict arises among social organisms when individuals differ in their inclusive-fitness interests. Ant societies are excellent models for understanding how genetic relatedness mediates conflict intensity. However, although conflicts within colonies typically arise over offspring production, the role of larvae as actors in social conflict has received little attention. We develop and empirically test kin-selection theory of larval egg cannibalism in ant societies. Specifically, we investigate how selection for cannibalism is mediated by nestmate relatedness and larval sex in a mathematical model and then test the model's predictions by measuring cannibalism levels in eight ant species with varying nestmate relatedness. In line with our theoretical predictions, cannibalism levels in larvae were significantly influenced by relatedness and sex. Increased relatedness was associated with reduced levels of cannibalism, indicating that larval behavior is mediated by inclusive-fitness considerations. Levels of cannibalism were significantly higher in male larvae, and our model suggests that this is due to sex differences in the benefits of cannibalism. By examining the selfish interests of larvae and the constraints they face in a social environment, our study presents a novel perspective on conflict in ants and on the evolution of selfish elements in social systems in general.

Do defensive chemicals facilitate intraguild predation and influence invasion success in ladybird beetles?

Egg predation and cannibalism are believed to be common phenomena among many species of aphidophagous predatory ladybird beetles despite the presence of alkaloid based defensive chemicals in all life stages. We identified defensive chemicals from eggs of three congeneric species, one introduced into North America (Coccinella septempunctata L.), and two native (C. transversoguttata richardsoni Brown, and C. novemnotata Herbst), and examined the effects of ingested defensive chemicals on first instars. Ingested congeneric alkaloids were not toxic to first instars, likely because the three congeners produce the same principal alkaloids, precoccinelline and coccinelline, in similar amounts. First instars of the three congeners accumulated alkaloids ingested through egg cannibalism and congeneric predation. Egg consumption doubled the amount of alkaloids in first instars when they fed on conspecific or congeneric eggs, in comparison to a pea aphid diet. No detrimental effects of ingested congeneric alkaloids on development or survival of first instars were observed among these congeners. Chemical defenses of eggs are therefore not likely to be important in favoring the invasive species, C. septempunctata, in interactions with these native congeneric species. Because the invasive species is the most aggressive predator, having the same types of alkaloids may facilitate disproportionate intraguild predation on native congeners by C. septempunctata thereby potentially enhancing the invasion success of this introduced species.

Egg Cannibalism inPomacea canaliculata(Caenogastropoda: Ampullariidae) from the Southern Pampas: An Alternative Trophic Strategy?

Pomacea canaliculata is a freshwater gastropod native to southern South America and is listed among the world's 100 worst invaders. Diverse food sources can be exploited by this apple snail, including snails with gelatinous and subaquatic egg masses. Records of ingestion of their own egg masses (egg cannibalism), which are aerial and calcareous, have only been anecdotal in P. canaliculata. Our aims were to study egg cannibalism in a natural population and also under laboratory conditions. In a stream population from the southern Pampas, we recorded P. canaliculata attacking their own fresh egg masses, which had been naturally submerged by an increase in water level. In addition, when we artificially submerged fresh and old egg masses in a field experiment, we observed several snails readily attacking both. In the laboratory, we also observed the capture by pedal surface collecting of floating remains of egg masses. In laboratory trials, juveniles fed on eggs reached larger sizes than starved snails but smaller than those fed on lettuce; adult snails also eat eggs, but their growth rates were not affected by the food regime. Pomacea canaliculata eggs present defensive and anti-nutritive compounds that apparently dissuade almost all potential predators, but this snail did not appear to be negatively affected when feeds on its own eggs. The ingestion of egg remains and submerged egg masses is probably more frequent than previously considered in P. canaliculata, which may take advantage of using these alternative food resources when others are scarce.

Preference for isolated host plants facilitates invasion ofDanaus chrysippus(Linnaeus, 1758) (Lepidoptera: Nymphalidae) by a bacterial male-killerSpiroplasma

Matrilinearly inherited endosymbiotic bacteria are estimated to occur in a third of all terrestrial arthropods. They include male killers, which are typically associated with organisms that lay their eggs in batches. Batch laying favours male-killing bacteria because infected female larvae can cannibalise dead brothers and do not have to compete with them for larval resources. This paper tackles the paradox of high male-killer infection rates in Danaus chrysippus (Linnaeus, 1758), a butterfly that lays its eggs singly rather than in batches, making the selective advantage of male killing for the bacterium hard to understand. The study was conducted in the Nairobi region of Kenya where two substantially allopatric but seasonally migratory semispecies of Danaus chrysippus overlap and hybridise. Within this hybrid zone, but apparently not outside it, D. chrysippus hosts the endosymbiotic male killer, Spiroplasma ixodetis. In Nairobi, this bacterium can infect up to 95% of females. Semispecies D. chrysippus chrysippus and its hybrid with D. chrysippus dorippus (form transiens) are heavily infected, unlike the parental pure D. chrysippus dorippus semispecies, which may be protected by a suppressor gene. We find that: (1) adult females oviposit preferentially on isolated host plants; (2) female larvae on isolated plants survive better than on plants growing in clumps; (3) female larvae survive in greater numbers on plants removed to the laboratory compared to plants left outside; (4) high Spiroplasma infection favours female survival; and (5) high egg/larval density adversely affects adult body size. We conclude that: (1) the butterflies' preference for isolated host plants creates high egg densities and hence enables invasion by Spiroplasma; (2) male killing favours female survival through cannibalism of male eggs and the extra food-plant resources so released; and (3) the butterfly's preference for isolated host plants may provide an enemy-free space that protects eggs and larvae from predators and parasitoids.

Filial cannibalism in a nest-guarding fish: females prefer to spawn in nests with few eggs over many

In fish, fecundity correlates with female body size and egg-tending males often eat small broods. Therefore, small females may prefer to spawn in nests that already contain many eggs, to ensure the brood is as large as possible. In contrast, large females may prefer nests with few eggs, if high egg number or density has a negative effect on egg survival, or if there are drawbacks of spawning last in a nest. To test the hypothesis that female body size affects nest (and male mate) choice, using the sand goby (Pomatoschistus minutus), we allowed small and large females to choose between two males that were matched in size — one guarding a small clutch and the other a large clutch, respectively. We recorded where females spawned (measure of female preference), the combined brood size, male courtship, egg care and nest building. We also quantified the effect of brood size and egg density on egg survival in a separate data set. Although the combined broods did not exceed the small brood sizes that are at risk of being eaten, both small and large females preferred to spawn in nests with smaller clutch sizes. This preference could not be explained by more courtship or male parental effort, nor by reduced survival of larger or denser broods. Instead, our result might be explained by females avoiding the danger of cannibalism of young eggs by males or the risk of reduced egg health associated with being near the nest periphery.

Does the Beach-Spawning Grunion Eat Its Own Eggs? Eighth Graders Use Inquiry-Based Investigation to Collect Real Data in a University Laboratory

A collaborative effort between a junior high school and a nearby university allowed 40 eighth-grade honors students to engage in a scientific investigation within a university laboratory. These students, with their science teachers and university researchers, gathered data on egg cannibalism in a beach-spawning fish and thereby contributed to an ongoing research project. Our objectives were to provide a scientific learning experience for the students and introduce them to a college setting. A survey, given 2.5 years after the investigation, found that most of the students had increased their interest in studying science in college.

Sublethal Exposure to Diatomaceous Earth Increases Net Fecundity of Flour Beetles (Tribolium confusum) by Inhibiting Egg Cannibalism

Population regulation results from an interplay of numerous intrinsic and external factors, and for many insects cannibalism is such a factor. This study confirms a previously-reported observation that sublethal exposure to the fossilized remains of diatoms (i.e. diatomaceous earth) increases net fecundity (eggs produced minus eggs destroyed/day) of flour beetles, Tribolium confusum. The aim was to experimentally test two non-mutually-exclusive ecological mechanisms potentially responsible for the increased net fecundity: higher egg production and lower egg cannibalism. Adult T. confusum were maintained at low or high density in medium containing sublethal (0–4%) diatomaceous earth. Net fecundity increased up to 2.1× control values during diatomaceous earth exposure, and returned to control levels following removal from diatomaceous earth. Cannibalism assays on adults showed that diatomaceous earth reduced the number of eggs produced to 0.7× control values at low density and to 0.8× controls at high density, and also reduced egg cannibalism rates of adults to as little as 0.4× control values, but at high density only. Diatomaceous earth also reduced cannibalism by larvae on eggs to 0.3× control values. So, while the presence of diatomaceous earth reduced egg production, net fecundity increased as a result of strong suppression of the normal egg cannibalism by adults and larvae that occurs at high beetle density. Undisturbed cultures containing sublethal diatomaceous earth concentrations reached higher population densities than diatomaceous earth-free controls. Cohort studies on survival from egg to adult indicated that this population increase was due largely to decreased egg cannibalism by adult females. This is the first report of inhibition of egg cannibalism by diatomaceous earth on larval or adult insects. The ability of diatomaceous earth to alter cannibalism behavior without causing mortality makes it an ideal investigative tool for cannibalism studies.

Egg cannibalism in a gull colony increases with sea surface temperature

Cannibalism occurs regularly across a broad range of taxa with a variety of ecological and evolutionary consequences. Rises in sea surface temperature (SST) have been linked to increased cannibalism in some species, including polar bears (Ursus maritimus), Peruvian anchovy (Engraulis ringens), and Peruvian hake (Merluccius gayi peruanus), and might be expected in birds that depend on marine food webs for sustenance. Increased SSTs are associated with lowered ocean thermoclines and weakened upwellings. These changes, in turn, lead to decreased productivity in surface water and movement of surviving forage fish to deeper water, thereby food-stressing surface feeders such as gulls, diminishing energy intake and lengthening foraging bouts. While controlling for a suite of other environmental factors, we tested whether egg cannibalism and hatching success were independent of rises in local SST at a colony of Glaucous-winged Gulls (Larus glaucescens) and Glaucous-winged × Western Gull (L. glaucescens × occidentalis) hybrids during 2006–2011 on Protection Island, Washington, USA. Cannibalism increased and hatching success decreased with rises in SST. It is unclear if rises in SST impact overall population trends. Gulls are multiyear breeders; if they experience reproductive failure during one or several El Niño-Southern Oscillation–related events, they typically have other opportunities to breed. With rising SSTs associated with climate change, however, increasing levels of cannibalism could lead to declining populations in the absence of compensatory adaptive modifications or range shifts.

Geographic Variation in Cannibalism in Colorado Potato Beetle (Coleoptera: Chrysomelidae) Populations

Cannibalism can have a large effect on population growth and survival in stressful environments, possibly including those created by insecticide use. In this study, we collected Colorado potato beetles from three isolated areas in the northeastern United States known for high levels of resistance to neonicotinoids. We measured resistance to imidacloprid in each of those populations, a laboratory susceptible population, and in hybrids between the three field populations and the laboratory susceptible population. We fed neonates eggs from resistant dams fed either imidacloprid-treated or untreated foliage to determine whether cannibals are exposed to toxins sequestered in eggs. We measured egg cannibalism by hatchlings within the clutch in each population and hybrids, and examined how fecundity and several variables associated with egg development varied among populations and with cannibalism, to see which traits might enhance or reduce cannibalism. Cannibalism varied significantly among populations, accounting for most of the variation in hatching success. Variability in egg development time and hatch rate in the absence of cannibalism in some populations affected rates of cannibalism. Resistance varied significantly among the field populations but was not related to cannibalism. Neonates fed eggs from dams on treated foliage showed signs of intoxication or death. Cannibalism appears to be part of a varying life history strategy in this species, with some populations laying larger and more cannibalistic clutches and the New York population laying smaller clutches with higher hatching success owing to reduced cannibalism.

Egg cannibalism in Acartia tonsa: effects of stocking density, algal concentration, and egg availability

Cannibalism in copepod culture may limit its production yield and therefore affect the economic interests associated with the use of copepods as live feed in aquaculture. The effects of adult density, egg density, and algal availability were tested on the calanoid copepod Acartia tonsa to understand how these parameters affect cannibalism rates on eggs. The overall cannibalism within the range of adult densities tested (120–1,000 adult L−1) was solely influenced by the egg and algal density, and not by the adult density. The increased densities of eggs lead to higher occurrences of cannibalism. Increasing the availability of alternative diets (e.g., algae) significantly diminished the adults’ cannibalistic behavior. The highest cannibalistic rates per adult were observed at low densities of adults and high densities of eggs (120 ind L−1 and 20,000 eggs L−1, respectively) and resulted in consumption rates >20 eggs ind−1 h−1. In this experiment, cannibalistic behavior reached 20 % of adult weight ind−1 h−1 under the aforementioned parameters. Additionally, the present study suggests that at high adult copepod density, the interactions between adults result in a decreased “time to feed.” Finally, it is argued that the separations of eggs from adult copepods, as well as the continuous access to an alternative food source, are necessary for decreasing the effects of cannibalism in copepod cultures.

Breeding Dynamics, Diet, and Body Condition of the Hong Kong Newt (Paramesotriton hongkongensis)

Paramesotriton hongkongensis has a highly restricted distribution in southern China, and a comprehensive study of the species' basic ecology in aquatic and terrestrial habitats has not been previously undertaken. Using mark-recapture methods, we assessed seasonal patterns of breeding populations in four streams in Hong Kong every 3 wk over 18 mo (2007–2009). We examined diet and body condition of newts in the four focal and six additional streams. We surveyed transects radiating outward from breeding pools to determine the extent of terrestrial habitats used. In the four focal streams, we made 3436 captures of adult newts, comprising 1312 unique individuals. Breeding occurred primarily during the dry, cool season and extended over 8 mo. Individuals remained in breeding pools for an average of 45 days, suggesting that populations in pools were changing throughout the breeding season and that most individuals had a 10-mo terrestrial phase. Sex ratio changed across the breeding season, with males making up larger proportions of populations earlier in the season. Breeding site fidelity averaged 24% and was density-dependent. Among the 47 identified prey types identified in the diet of 406 newts, the most important prey were Brotia snails, Caridina shrimp, newt eggs, baetid mayflies, and calamoceratid caddisflies, in composite making up 63% of total prey volume and 82% of total prey abundance. Cannibalism of eggs and larvae, primarily by females, largely explained differences in diet between sexes. We documented no systematic difference in adult body condition (size-weight relationship) among streams. Fifteen individuals were found in forested habitats within 100 m of the nearest stream, except a single individual located 228 m away. Our work demonstrates that P. hongkongensis occurs at relatively high densities in stream pools during a protracted breeding season, in which individuals show site fidelity but probably do not breed every year. The species appears to be a generalist predator in most aquatic habitats. Although individuals spend most of the year on land, we still have little understanding of the spatial extent of terrestrial habitat use by the species. Future investigations should focus on the species' ecology in terrestrial habitats and on determining the amount of forest cover around breeding sites necessary to protect P. hongkongensis populations in Hong Kong.

A first step towards improving copepod cultivation using modelling: the effects of density, crowding, cannibalism, tank design and strain selection on copepod egg production yields

Copepods are the optimal live feed for hatcheries and improvement of cultivation techniques, to provide a constant food source, is crucial for the expansion of the industry. However, studies based on experimental work and real observations can be labour intensive and expensive. A simple model was developed based on the well-known life history traits of Acartia tonsa to describe batch cultures and their productivity. Model results were compared to observations from real cultures. For maximizing egg production yields, the optimal stocking density of copepods should be adapted to the design (depth) of the culture tanks. At high densities, stress due to encountering conspecifics, as well as cannibalism of eggs by adults, limits egg production yields. Using this model, the potential selection efficacy of copepod strains was also evaluated in order to increase production yields. Selecting larger copepods increases the egg production per litre of culture, but decreases the optimal stocking density and the range of densities at which egg production yield is high, and vice-versa. Selecting copepods that are less affected by stress due to conspecifics only affect production yields at very high adult densities. However, selecting copepods with a high Specific Growth Rate (SGR), or improving their SGR, was found to be an alternative which did not affect the optimal cultivation densities but improved egg production yields.

On the population dynamics, reproductive biology and growth of Succinea putris (Linnaeus, 1758) (Gastropoda: Pulmonata: Succineidae)

Selected life-cycle and population parameters of a common Euro-Siberian wetland snail – Succinea putris (L.) – were studied in the field and in the laboratory. In the field the snails reproduced at least from April till September, with April–May and August–September peaks; only one such peak (April) was observed in the laboratory, though the snails reproduced throughout the year. The changes in population size structure in the field and the laboratory results (life span 210–420 days, mean 309) indicated semelparity. Growth in the laboratory included two phases: slow (November–March) and fast (June–October); which phase came first during the life cycle depended on the date of hatching. The growth rate in the field corresponded closely with the fast-phase growth in the laboratory. The smallest reproducing individual was slightly over 2.8 whorls; snails of 3.0 whorls were regularly observed to produce eggs (maximum number of whorls in adults: 4.0). Sexual maturity was attained in ca. 160 days. The eggs (non-calcified, translucent, spherical, 1.7–2.0 mm in diameter) were laid in batches, 5–64 per batch; the eggs within a batch were glued together. The batch dimensions were 3.5–25.7×2.2–24.7 mm. The time to lay a batch was 20–35 minutes. Forty-eight snails produced 74 batches within 12 months. The duration of the egg phase was 11–28 days, which might indicate egg retention of varied duration; hatching was asynchronous, spanning 1–12 days within a batch. The hatchlings had shells of 1.1–1.2 whorls; hatching success was 95%. Neither uniparental reproduction, nor egg or juvenile cannibalism were observed. When compared to data in the literature, our results imply that Succinea putris displays substantial local variation in life-cycle traits. We also provide an overview table to discuss similarities and adaptive radiation in the European succineid species.

Kinship reduces alloparental care in cooperative cichlids where helpers pay-to-stay

Alloparental brood care, where individuals help raising the offspring of others, is generally believed to be favoured by high degrees of relatedness between helpers and recipients. Here we show that in cooperatively breeding cichlids, unrelated subordinate females provide more alloparental care than related ones when kinship between dominant and subordinate group members is experimentally manipulated. In addition, unrelated helpers increased alloparental care after we simulated egg cannibalism by helpers, an effect not shown by related helpers. By supporting predictions of pay-to-stay theory, these results suggest that in Neolamprologus pulcher, reciprocal commodity trading is important for the decision of subordinates to invest in care of the dominants' offspring.

Social conflict in ant larvae: egg cannibalism occurs mainly in males and larvae prefer alien eggs

In social organisms, cooperation is widespread. However, social groups also provide excellent opportunities for individuals to exploit the cooperative efforts of others, thus creating conflict. Social conflict is particularly common in ant societies but although much is known about conflicts between adult individuals, the selfish interests of developing offspring have been largely neglected. One taxonomically widespread way for offspring to engage in competition is through egg cannibalism. Here, we show that larvae of the ant Formica aquilonia compete by eating eggs, which increases their survival. Cannibalism behavior differs strongly between sexes, and males cannibalize 3 times as often as females. This points to sex-dependent benefits from cannibalism, for males possibly through removal of future competitors for mating opportunities. Larvae also preferentially eat eggs of distinct origin and odor profile, suggesting that they can detect and react to chemical cues. Thus, similar to adult ants, larvae possess the power to adjust their behavior to available information. We conclude that exploring the behavior of developing individuals can give new insight into social conflict in ants and social animals in general.

Presence of conspecific females motivates egg cannibalism owing to lower risk of filial cannibalism

A cannibal has to weigh the benefits of the consumption and removal of competing conspecifics against the potential loss of fitness through filial cannibalism. We examined the role of the presence of conspecific females in informing adaptive cannibalism decisions. Females of the hemipteran bug Geocoris pallens express low egg cannibalism when alone but become much more cannibalistic in the presence of conspecific females and do not discriminate between their own eggs and those of other females. Experimentation showed that females that could not commit filial cannibalism exhibited strong egg cannibalism that was not reduced by the presence of conspecific females, whereas females that could commit filial cannibalism were very cannibalistic only in the presence of conspecifics. An experiment also showed that the presence of conspecific females triggered a stronger egg cannibalism response in G. pallens than did a heterospecific egg predator. These results suggest that G. pallens females become cannibalistic in the presence of conspecifics because they interpret conspecific presence primarily as an indication of decreased likelihood of committing filial cannibalism, and less so as an indication of lower expected survival of eggs or future resource competition. Our study highlights the importance of informational cues, in this case the presence of conspecifics, in modulating the expression of cannibalism.

Fitness consequences of sibling egg cannibalism by neonates of the Colorado potato beetle, Leptinotarsa decemlineata

Egg cannibalism is a widely observed behaviour in nature that provides nutritional benefits without the costs of subduing prey. However, when egg cannibalism involves sibling eggs, the benefits obtained must balance inclusive fitness losses. Neonates of the Colorado potato beetle, Leptinotarsa decemlineata , readily consume other eggs within their natal clutch. To explore the fitness consequences of this behaviour, neonates were fed no, one, or two eggs upon hatching, along with their normal diet of potato foliage. Daily mass, the time to each moult, adult volume and mass, and fecundity were measured for each individual, along with mortality rates. Cannibals gained mass more quickly and reached each developmental stage 1 day earlier than noncannibals. No benefits at the adult stage (other than earlier emergence) were observed, and there were no sex differences in the benefits of cannibalism. Mortality was not reduced by cannibalism under laboratory conditions. A simulation demonstrated that when the mortality risk is high, decreased development time due to cannibalism can reduce this risk sufficiently to balance the inclusive fitness loss of eating a single half-sibling. Additional benefits of cannibalism, such as reduced competition, need to be investigated to fully explain cannibalism of multiple sibling eggs. ► Beetle neonates fed eggs gained mass more quickly than those fed only foliage. ► Cannibals reached each developmental stage at least 1 day faster than noncannibals. ► No sex differences were observed in the benefits of cannibalism. ► The observed development-time benefits compensate for the death of a half-sibling.

Effects of Flour Conditioning on Cannibalism of <I>T. castaneum</I> Eggs and Pupae

Cannibalism is a very important factor regulating population dynamics of the red flour beetle. After several days of feeding, the flour becomes conditioned by the beetles, which can affect rates of cannibalism. Flour conditioning is caused by an accumulation of feces, pheromones, and ethylquinone, which is a repellent produced by the beetles. We determined the effect of five different levels of flour conditioning on cannibalism of red flour beetle eggs and pupae by adult and larval stages. Larvae had the highest rates of egg cannibalism (12 eggs eaten over the 4-d period) followed by female adults (seven eggs consumed). Adult males had the lowest rates of cannibalism with only two eggs consumed. Cannibalism of eggs by females was correlated negatively with the level of flour conditioning. There was no effect of flour conditioning on egg or pupal cannibalism by larvae or adult males. Cannibalism by adult females may decrease as the level of flour conditioning increases because females may spend less time tunneling in highly conditioned flour and more time trying to disperse to other areas that are better for oviposition.

Parental care trade-offs and the role of filial cannibalism in the maritime earwig, Anisolabis maritima

Animals that provide parental care are expected to weigh the value of current offspring against the value of future offspring, such that total investment across all offspring is allocated to maximize lifetime fitness. In this study, we characterize the trade-offs associated with maternal care in the maritime earwig, Anisolabis maritima (Dermaptera: Anisolabididae). We measured the benefits of care in terms of hatching success through removal experiments and the costs of care by comparing the future fecundity of caring females to that of removals. We show that the benefits of care greatly outweigh the costs, providing a seven-fold increase in hatching success. Artificially removed females had larger subsequent clutches and shorter internest intervals, but very low hatching success. Naturally abandoning females always cannibalize all their eggs. Partial clutch cannibalism was a ubiquitous feature of maternal care, although rates were variable among individuals. In post hoc tests, we first addressed the ultimate explanation that filial cannibalism is a way for females to facultatively adjust their investment per clutch in order to maximize future reproduction. We then tested two proximate explanations for filial cannibalism: (1) females that lay more eggs for their given body size tend to consume more eggs, reflecting a nutritional deficiency; (2) females prefer to cannibalize the youngest eggs to reduce the overall duration of egg care. In addition, we consider the alternative explanation that females eat unviable eggs for hygienic reasons. Our results provide support for both energy limitation and hygienic maintenance. Higher rates of egg cannibalism near the very end of nesting were also suggestive of nymphal cannibalism, a phenomenon that will be examined in future work.