Changes in nectar concentration: how quickly do whitebellied sunbirds (Cinnyris talatala) adjust feeding patterns and food intake?

Nectarivorous birds encounter varying nectar concentrations while foraging on different food plants and must adjust their consumption to maintain constant energy intake. We determined how rapidly captive whitebellied sunbirds (Cinnyris talatala) adjust their volumetric intake and feeding patterns after changes in diet concentration. On four consecutive days, birds were fed sucrose diets alternating between a standard diet of 16% w/w and test diets of 2.5, 8.5, 16 or 30% w/w, respectively, for 1.5 h periods. Feeding events were recorded with an infrared photo-detection system and food intake and body mass were monitored continuously by electronic balances interfaced to a computer. Generally, birds demonstrated a measurable increase in feeding frequency and food intake within 10 min after a decrease in sucrose concentration. However, individuals responded differently to the most dilute diet (2.5%): while most increased their food intake, others stopped feeding for a short while, appearing to dislike this diet. Furthermore, the number and duration of feeding events increased in the first 5 min after the switch from 2.5% back to 16%, as the birds attempted to compensate for previous reduced sugar intake. Daily sugar intake was lower when birds alternated between 2.5 and 16% diets than on other test days, but birds were able to maintain body mass, presumably through behavioural adjustments.     

Stearolyl-CoA desaturase: a control enzyme in hepatic lipogenesis.

1. Hepatocytes were isolated by perfusion of the liver with collagenase/salt solutions and incubated in culture after attachment to plastic culture dishes for periods up to 48 h. 2. The cells, when incubated in serum-free culture medium in the presence of insulin, showed enhanced stearolyl-CoA desaturase activity which was not observed when 50 muM cycloheximide was included. When insulin was omitted from the medium, the cells lost 80% of their original desaturase activity. 3. Cells isolated from animals fed 20% (w/w) sucrose for two weeks prior to sacrifice, showed high levels of fatty acid synthesis, stearolyl-CoA desaturase activity and triacylglycerol synthesis when compared with cells isolated from animals fed a corn oil supplemental diet. 4. The observations are discussed in terms of the influence of stearoyl-CoA desaturase activity on hepatic lipogenesis.     

Influence of experimental context on the development of anhedonia in male mice exposed to chronic social stress

Consumption of 1% sucrose solution supplemented with 0.2% vanillin was studied in two experimental contexts in male mice living under chronic social stress induced by daily experience of defeats in agonistic interactions and leading to development of depression. In the first experiment, vanillin sucrose solution was made available as an option along with water during 10 days for mice living in group home cages. Then the mice were subjected to repeated social defeat stress and during exposure to stress they were provided with both vanillin sucrose solution and water using a free two-bottle choice paradigm. In the other experiment, vanillin sucrose solution was first offered to mice after 8 days of exposure to social defeat stress. Males familiar with vanillin sucrose solution showed vanillin sucrose preference while experiencing defeat stress: consumption of vanillin sucrose solution was about 70% of total liquid consumption. However, the consumption of vanillin sucrose solution per gram of body weight in mice exposed to social stress during 20 days was significantly lower than in control males. In the second experiment, males after 8 days of social defeat stress were found to consume significantly less vanillin sucrose solution as compared to control males. On average, during two weeks of measurements, vanillin sucrose solution intake was less than 20% of total liquid consumption in males. Consumption per gram of body weight also appeared to be significantly lower than in control group. The influence of experimental context on the development of anhedonia measured as a reduction of sucrose solution intake by chronically stressed male mice is discussed.     

Effects of sequential feeding with low- and high-protein diets on growth performances and plasma metabolite levels in geese

This study was conducted by two trials to investigate effects of sequential feeding with low- and high-protein diets on growth traits and plasma metabolites in geese. In Trial I, the effect of sequential feeding under time-restricted feeding system was investigated. Seventy-two White Roman goslings were randomly allotted into either sequential feeding (S1) or control feeding (C1) group. All goslings were fed for 1 h at morning and at evening, respectively, from 2 to 8 weeks of age. S1 group was offered 13% CP diet at morning and 19% CP diet at evening. C1 group was offered the same diet (16% CP; mixed equally with the two diets mentioned above) at both morning and evening. Blood samples were hourly collected for 4 h after feeding at both morning and evening for the determination of the postprandial plasma levels of glucose, triacylglycerol and uric acid at the end of experiment. Results showed that BW, average daily gain (ADG), and daily feed intake (FI) were not different between groups, but the feed efficiency (FE) in S1 group was significantly higher than that in C1 group (P<0.05). The areas under curve (AUC) of plasma postprandial levels of glucose, triacylglycerol and uric acid were not affected by treatment, but the AUC of triacylglycerol and uric acid in morning were lower than those in evening (P<0.05). In Trial II, the effect of sequential feeding under ad libitum feeding system was investigated. Twenty-four goslings were randomly allotted into either sequential feeding (S2) or control feeding (C2) group. Diets were altered at 0600 and 1800 h, respectively, and geese were fed ad libitum from 4 to 8 weeks of age. S2 group was offered 14% CP diet at morning and 20% CP diet at evening. C2 group was supplied the same diet (mixed with the two diets according to the ratio of diets consumed by S2 group on the preceded day) at both morning and evening. Results showed that the ADG in S2 group was higher than those in C2 group (P<0.05). Summarized data from both trials showed that sequential feeding improves daily gain and FE in growing geese.     

Arginine metabolism by the corn stunt spiroplasma

When corn stunt spiroplasma (CSS) was grown in spiroplasma medium A (SMA) containing 5% horse serum, 16% sucrose, 1.5% PPLO broth, and 0.002% phenol red indicator, color and pH of the medium changed from red (pH 7.5) to yellow (pH 5.8) by 4 days after inoculation with CSS. In spiroplasma medium B (SMB), identical to SMA except for supplementation with 47 mM arginine-HCl, color and pH changed within 4 days but reverted to red (pH 7.5) 6 days later, suggesting that arginine was metabolized. Growth of CSS in both SMA and SMB was a characteristic sigmoid pattern; maximum titers were reached the fifth day after inoculation and were 2.3 × 10⁸ cells/ml in SMA and 4.5×10⁸ cells/ml in SMB. Helicity and motility of CSS were lost after 8 days in SMA, while in SMB some cells were still helical and motile up to 15 days. Daily analyses of CSS cultures by photometric methods showed that arginine was depleted from SMB and production of ammonia and ornithine was higher in SMB than in SMA; citrulline was detected in SMB but urea was not found in either medium. Results from additional tests using an amino acid analyzer and thin-layer chromatography further substantiated arginine metabolism and indicated that an arginine deiminase pathway was operative in CSS.     

Induction of salivary gurmarin-binding proteins in rats fed gymnema-containing diets.

Gymnema sylvestre, a tropical plant, contains gurmarin that selectively suppresses sucrose responses of the chorda tympani nerve in rats and mice. We investigated preference for taste solutions and saliva composition in rats fed a diet containing this plant (gymnema diet). Preference for 0.01 M sucrose and a mixture of 0.03 M sucrose and 0.03 mM quinine-HCl significantly decreased at 1-2 days after the start of the gymnema diet and subsequently returned closely to the control levels within about a week. There was no significant change in preference for NaCl, monosodium glutamate and quinine-HCl during feeding trials. Submandibular saliva of rats fed the gymnema diet for 4 and 14 days showed an inhibitory effect on immunoreaction between gurmarin and antigurmarin serum. Analyses using electrophoresis and affinity chromatography indicated that the saliva contains gurmarin binding proteins with molecular weights of 15, 16, 45, 60 and 66 kDa. These results suggest that reduction of preference for sucrose was probably caused by gurmarin contained in the gymnema diet and subsequent restoration of the preference may be due to suppression of the effect of gurmarin by salivary gurmarin-binding proteins induced by the gymnema diet.     

Dietary fish oil normalize dyslipidemia and glucose intolerance with unchanged insulin levels in rats fed a high sucrose diet

The aim of this study was to investigate the relationship between the lipid-lowering effects of fish oils and concomitant consequences on glucose tolerance and insulin sensitivity in an experimental animal model of hypertriglyceridemia induced by high sucrose intake. To achieve this goal, male Wistar rats were fed a semi-synthetic sucrose rich diet (SRD) (w/w: 62.3% sucrose, 8% corn oil, 17% protein) for 90 days. At the time, a well established and permanent hypertriglyceridemia accompanied by glucose intolerance was present. After that, one half of the animals continued on the SRD up to 120 days. The other half received an SRD in which the source of fat was substituted by cod liver oil (w/w 7% CLO plus 1% corn oil) from day 90 to 120 (SRD + CLO). Control rats were fed a semi-synthetic diet (CD) (w/w: 62.5% corn starch, 8% corn oil, 17% protein) throughout the 120 days experimental period. Results obtained after the experimental period show that the hypertriglyceridemia and glucose intolerance ensuing long term feeding normal rats with a sucrose-rich diet could be completely reversed mediating no change in circulating insulin levels by shifting the source of fat in the diet from corn oil to cod liver oil. These findings suggest that manipulation of dietary fats may play a role in the management of the lipid disorders associated with glucose intolerance and insulin resistance.     

Sucrose hydrolysis does not limit food intake by Pallas's long-tongued bats

Nectarivorous bats include very dilute nectar in their natural diet, and recent work with Pallas's long-tongued bat Glossophaga soricina showed that sugar (energy) intake rate decreased at dilute sucrose solutions. However, chiropterophillous nectar is composed mainly of the hexoses glucose and fructose. Because bats fed hexose nectar would save the delay of hydrolyzing sucrose, we hypothesized that sugar intake rate should be higher on this diet than on sucrose nectar. We compared intake response in Pallas's long-tongued bats offered 1 : 1 glucose-fructose (hexose) and sucrose diets at 5%, 10%, 20%, 30%, and 40% (mass/volume) sugar solutions. We also tested the hypothesis that sucrose hydrolysis limits food intake in bats. Intake response was the same in bats fed both types of diet: sugar intake rate was lower in dilute solutions and then increased with sugar concentration. Similar intake responses in both diets indicate that sucrose hydrolysis alone does not limit food intake and support the idea that the burden of processing excess water in dilute solutions plays a major role.     

Photoperiod Regulates Lean Mass Accretion,but Not Adiposity,in Growing F344 Rats Fed a High Fat Diet

In this study the effects of photoperiod and diet, and their interaction, were examined for their effects on growth and body composition in juvenile F344 rats over a 4-week period. On long (16L:8D), relative to short (8L:16D), photoperiod food intake and growth rate were increased, but percentage adiposity remained constant (ca 3-4%). On a high fat diet (HFD), containing 22.8% fat (45% energy as fat), food intake was reduced, but energy intake increased on both photoperiods. This led to a small increase in adiposity (up to 10%) without overt change in body weight. These changes were also reflected in plasma leptin and lipid levels. Importantly while both lean and adipose tissue were strongly regulated by photoperiod on a chow diet, this regulation was lost for adipose, but not lean tissue, on HFD. This implies that a primary effect of photoperiod is the regulation of growth and lean mass accretion. Consistent with this both hypothalamic GHRH gene expression and serum IGF-1 levels were photoperiod dependent. As for other animals and humans, there was evidence of central hyposomatotropism in response to obesity, as GHRH gene expression was suppressed by the HFD. Gene expression of hypothalamic AgRP and CRH, but not NPY nor POMC, accorded with the energy balance status on long and short photoperiod. However, there was a general dissociation between plasma leptin levels and expression of these hypothalamic energy balance genes. Similarly there was no interaction between the HFD and photoperiod at the level of the genes involved in thyroid hormone metabolism (Dio2, Dio3, TSHβ or NMU), which are important mediators of the photoperiodic response. These data suggest that photoperiod and HFD influence body weight and body composition through independent mechanisms but in each case the role of the hypothalamic energy balance genes is not predictable based on their known function.     

Invertase and sucrose synthase in flowers

Sucrose and reducing sugar concentrations in petals of cut carnation flowers, whose life was prolonged up to 7 days by bathing stalks in sucrose solutions, were respectively 3-fold and 2-fold higher than those bathed in water. Reducing sugar concentrations were about 7-fold higher than sucrose concentrations. A study of invertase and sucrose synthase activities in flower petals of carnation and four other species of flowers revealed that both enzymes may be involved in hydrolysis of translocated sucrose. Invertase activity, while being up to 20-fold higher than sucrose synthase activity in some species was approximately comparable in others. More detailed studies on invertase from petals of 3 flower species demonstrated the presence of only the acid form of the enzyme with a K_m value for sucrose of about 2.5 mM.     

Long-term regulation of sucrose intake by the female mosquito, Aedes taeniorhynchius

Newly emerged female Aedes taeniorhynchus were maintained in cups provided with potometers containing 5, 10, and 25% sucrose solutions. Mortality and the ab lib. intake of sucrose were recorded daily and groups were sampled at regular intervals for analysis of energy reserves.After a week of relatively substantial intake of sucrose at all three concentrations, a constancy in daily intake at much lower levels was observed during the next 4 weeks. The caloric intake was highest in the 25% sucrose solution group. There were no differences in mortality rates at these concentrations. Glycogen (0·7–1·0 cal/female) and triglycerides (3·5dash4 cal/female) reserves reached maximum levels after the first week and stabilized thereafter on all three concentrations. In this species the stabilization in intake of sucrose solution after the first week is correlated with the maximum accumulation of stored energy reserves as opposed to decreased activity or subtle changes associated with senescence.     

Enhanced initial and sustained intake of sucrose solution in mice with an oxytocin gene deletion

Laboratory mice drink little sucrose solution on initial exposure, but later develop a strong preference for sucrose over water that plateaus after a few days. Both the initial neophobia and later plateau of sucrose intake may involve central oxytocin (OT) signaling pathways. If so, then mice that lack the gene for OT [OT knockout (KO)] should exhibit enhanced initial and sustained sucrose intake compared with wild-type (WT) cohorts. To test this hypothesis, female OT KO and WT mice (11-13 mo old) were given a two-bottle choice between 10% sucrose and water available ad libitum for 4 days. On the first day, sucrose intake was 20-fold greater in OT KO mice compared with WT cohorts. The avid sucrose consumption by OT KO mice increased further on day 2 and was sustained at significantly higher levels than intake by WT mice. Enhanced initial and sustained sucrose intake also was observed in 5- to 7-mo-old male OT KO mice. The effect of genotype was observed over a range of sucrose concentrations and was maintained over at least 8 days of continual exposure. However, there was no effect of genotype on daily intake of sucrose-enriched powdered chow. These findings indicate that the genetic absence of OT in mice is associated with enhanced initial and sustained intake of sucrose solutions. Thus central OT pathways may normally participate in limiting initial intake of novel ingesta and may also participate in limiting intake of sweet, highly palatable familiar ingesta.     

Breeding ecology of the Sulawesi Red-Knobbed Hornbill Aceros cassidix

Data are presented for a four-year study of the breeding biology of the Sulawesi Red-knobbed Hornbill Aceros cassidix. The breeding season normally began in mid-June and lasted 27–30 weeks. Initiation of nesting appeared to be stimulated by the cessation of the rains and timed such that chicks emerged during a period of fruit abundance. Nesting period averaged 139 days and incubation was estimated at 35–40 days. Females remain sealed in the nest for an average of 108 days and nestlings fledged, on average, 28 davs after the female emerged. Nesting densities were up to 10.4/km², nesting success was high (up to 80%) and repeated use of nests between years was common. Males delivered a low-protein diet of ripe fruits (89% of total diet) from 12 families and 52 species; invertebrates composed only 1% of food items. Figs ( Ficus spp.) were the primary diet item, accounting for 81% of fruit biomass. Males increased feeding visits throughout the study, but the biomass of fruit delivered declined shortly after the female emerged. Reduced feeding prior to fledging may entice the nestling to emerge. The long developmental period of Sulawesi Red-knobbed Hornbills may result, in part, from the low protein content of the diet. Despite a 16% annual production, numbers in the study area have remained stable over the past 15 years. It is suggested that high post-fledging mortality or dispersal to degraded areas outside the reserve maintains population numbers. Distinguishing between these mechanisms is important for understanding the dynamics of hornbill populations.     

Changes in Soybean (Glycine max [L.] Merr.) Glycerolipids in Response to Water Stress

Soybean (Glycine max [L.] Merr.) plants with the first trifoliate leaf fully expanded were exposed to 4 and 8 days of water stress. Leaf water potentials dropped from −0.6 megapascal to −1.7 megapascals after 4 days of stress; then to −3.1 megapascals after 8 days without water. All of the plants recovered when rewatered. The effects of short-term drought stress on triacylglycerol, diacylglycerol, phospholipid, and galactolipid metabolism in the first trifoliate leaves was determined. Leaf triacylglycerol and diacylglycerol content increased 2-fold during the first 4 days of stress and returned to control levels 3 days after rewatering. The polar lipid fraction, which contained phospholipids and galactolipids, changed little during this time. The linolenic acid (18:3) content of the triacylglycerol and diacylglycerol increased 25% during stress and the polar lipid 18:3 content decreased 15%. The pattern of glycerolipid labeling, after applying [2-¹⁴C]acetate to intact leaves was altered by water stress. After 4 days of water stress the radioactivity of phosphatidic acid + phosphatidylinositol, phosphatidylcholine, triacylglycerol, and diacylglycerol increased between 4 and 9% (compared to control plans) while radioactivity of phosphatidylethanolamine, monogalactosyldiglyceride, and digalactosyldiglyceride decreased 2 to 11%. These data indicated that increased levels of triacylglycerol and diacylglycerol observed during water stress were attributed to de novo synthesis rather than breakdown or reutilization of existing glycerolipids and fatty acids.     

The effects of diet on the esterification of glycerol phosphate, dihydroxyacetone phosphate and 2-hexadecylglycerol by homogenates of rat adipose tissue.

1. Male rats were fed for 5 weeks after weaning on a diet containing (by weight) 59% of starch or on diets that contained 39% of starch and 20% of either sucrose, beef tallow or corn oil. 2. The rats fed on the beef tallow consumed more energy than did the rats fed on the starch and sucrose diets. The rats fed on the corn oil drank less water than did the other groups of rats. 3. There were no significant differences between the four groups in terms of body-weight gain, epididymal-fat-pad weight and in the size, number and triacylglycerol content of the adipocytes in the fat-pads. 4. There was a significant correlation (P less than 0.001) between the activities of glycerol phosphate acyltransferase and monoacylglycerol acyltransferase in individual rats. Both of these activities were highest in the group fed on the high-starch diet and both correlated with the consumption of glucose by individual rats in the four groups. 5. The percentage of glycerol phosphate converted into diacylglycerol and triacylglycerol was positively correlated with the mean diameters, surface area and triacylglycerol content of the adipocytes for individual rats and was greates in the sucrose-fed rats. 6. The specific activity of dihydroxyacetone phosphate acyltransferase was highest in the rats fed on beef tallow. This activity was positively correlated with the energy intake for all dietary groups over the 5-week feeding period. 7. The results are discussed in terms of the functions of the three routes of glycerolipid synthesis in adipose tissue.     

Rapid calorie metering inad lib rats

Adult wistar rats of either sex housed in individual cages and fedad lib were used to investigate the effects of calorie content and taste on ingestion. A 15 min single-choice solution (water, quinine, sucrose, saccharin) test as well as 1 h mixed diet (stock diet, sucrose-mixed, saccharin-mixed, quinine-mixed) tests were used. Calorically-rich sucrose either in solution or in mixed-diet was preferentially ingested. Tasteper se has not influenced calorie intake, as intake on sweet saccharin (3.4 ±0.4 cal) or on bitter quinine (3.3 ±0.6 cal) was similar to intake on stock diet (4.8 ±0.8 cal). Increased 5 min intake on sucrose solution (4.6 ±0.1 ml) over intake of other test solutions (saccharin 3.5 ±0.2 ml, quinine, 1.2 ±0.3 ml, water 2.1 ±0.1 ml) and calorie intake suppression on 1 h stock diet immediately following sucrose solution intake, indicate rapid calorie metering, probably based on fast-acting specific gustatory signals     

Sexual differences in over-winter torpor patterns of Richardson's ground squirrels in natural hibernacula

Summary Over-winter torpor patterns of Richardson's ground squirrels hibernating in southern Alberta were monitored with temperature-sensitive radiocollars to determine if these patterns differed between males and females in a manner related to the greater costs of mating effort by males than females. The hibernation season (from immergence to emergence) was composed of three periods: post-immergence euthermy, heterothermy, and pre-emergence euthermy. The hibernation season was shorter for juveniles than adults both among males (< 150 versus 234 days) and females (185 versus 231 days), a reflection of the later immergence into hibernation by juveniles. However, regardless of the absolute duration of hibernation, heterothermy accounted for a smaller proportion of the hibernation season of males (93±5%) than females (98±1%) and, within the heterothermal period, males had shorter torpor bouts and longer inter-torpor arousals. Overall, males spent a smaller proportion of the hibernation season in torpor (85±6%) than females (92±1%). This sexual difference was largely attributable to the longer duration of preemergence euthermy for males than females. Males terminated torpor in January and February, when hibernacula were at their coldest, then remained euthermic for 8.8 days (range 0.5–25.0 days) before emergence. In contrast, females terminated torpor in March, when hibernaculum temperatures were increasing, then remained euthermic for only 1.1 days (range 0.5–2.0 days) before emergence. Males lost less mass per euthermic day during hibernation than females (7.0 versus 9.3 g/day). Males and females hibernated at similar depths (56 cm), but males had larger chambers than females (18 versus 16 cm³/g). Many males, but no females, cached seeds in the hibernaculum. Males met the costs of thermogenesis and euthermy from a combination of fat reserves and food caches, whereas females relied solely on fat. Access to food caches permitted males to terminate torpor several weeks in advance of emergence, during which time they recouped mass and developed sperm in preparation for the forthcoming mating season.     

Effect of sugars in the preservation solution on liver storage in rats.

We have performed 128 rat liver transplants in order to examine the effect of sugars in preservation solutions on cold storage of rat livers. Glucose (Mw. 180), sucrose (Mw. 348), and raffinose (Mw. 594) were tested. Rat livers were preserved at 4 degrees C for 12, 16, 18, and 24 h in standard Eurocollins solution (EC solution) (solution A) or in one of three modified EC solutions in which 194 mM/liter glucose in standard EC solution was replaced by 140 mM/liter of glucose (solution B), sucrose (solution C), or raffinose (solution D). The osmolarity of the modified solutions (solution B-D) was 320 mOsm/liter. Using standard EC solution (solution A), the 1-week survival rate of rats receiving livers preserved for 12, 16, 18, or 24 h was 6/8, 4/8, 1/8, and 0/4, respectively. With solution B, in which 194 mM/liter glucose was replaced by 140 mM/liter glucose, 1 week survivors following transplantation of livers preserved for 12, 16, 18 or 24 h were 4/8, 3/8, 2/8 and 0/4, respectively. Solution C, which was identical to solution A except for the replacement of 194 mM/liter glucose by 140 mM/liter sucrose, gave the following 1-week survival rates: 5/8 for 12 h, 5/8 for 16 h, 2/8 for 18 h, and 0/4 for 24 hours preservation, respectively. Using solution D, which differed from A in the replacement of glucose by 140 mM/liter raffinose, the 1-week survival rates of rats grafted with livers preserved for 12, 16, 18, and 24 h were 6/8, 5/8, 3/8 and 0/4, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of age and diet on respiration in adult male and female blowflies, Phormia regina

Female Phormia regina, in general, were found to utilize more oxygen than males especially after approximately the sixth day of adulthood on both a μl/specimen and μl/mg basis. The females exhibited cyclic respiratory rates which correlated with the gonadotrophic cycles. Following its final gonadotrophic cycle the respiratory rates of females progressively declined. The male exhibited its highest respiratory rates during the fifth and tenth days after emergence; thereafter, there was a general decline in respiratory rates. Females have a significantly higher fresh body weight than males when both sexes are fed on a protein diet.Females fed on a protein-deficient diet exhibited significantly higher respiratory rates on a μl/mg basis than females fed on a protein diet. This extremely high respiratory rate was directly correlated with the occurrence of a protein hunger drive. Males fed on a protein-deficient diet also exhibited higher respiratory rates on a μl/mg basis than males fed on protein diet. However, the differences were not as great between the males as compared to the female comparison.     

Sugar concentration and timing of feeding affect feeding characteristics and survival of a parasitic wasp

The availability of food sources is important for parasitoid survival, especially for those that inhabit ecosystems where nectar and honeydew are spatially or temporally scarce. Therefore, the value of even a single meal can be crucial for survival. Psyttalia lounsburyi is a parasitoid, and biological control agent, of the olive fruit fly, Bactrocera oleae. In order to improve our understanding of the basic nutritional ecology of P. lounsburyi and its role in survival we evaluated the effect of a single sucrose meal on the longevity of female and male wasps. We measured the duration of feeding, volume ingested, sucrose consumption, energy content, and longevity of wasps provided with different concentrations of sucrose (0.5, 1, and 2 M) at different times after emergence (0, 1, 2 or 3 days after emergence). Our results showed that longevity was significantly influenced by sucrose concentration and timing of feeding. For females, feeding on sucrose increased the likelihood of survival to varying degrees, ranging from 32.3% to 95.4%, compared to water-only controls. The longest duration of feeding was observed for the highest sucrose concentrations and oldest wasps. The amount of sugar ingested and energy uptake increased, up to a point, as sugar concentration increased. Our results suggest that P. lounsburyi derived greatest benefit from the intermediate concentration (1 M) of sucrose provided 2 or 3 days after emergence. Our study emphasizes the importance of finding balance between increasing longevity and limiting the duration of feeding, and concomitant uptake of nutrients, that is fundamental for survival of the wasp in nature.