Modulation of leucine absorption in the larval midgut of Bombyx mori (Lepidoptera, Bombycidae).

In the larval midgut of Bombyx mori a K(+)-dependent transporter for leucine and amino acids with a hydrophobic side chain is responsible for the absorption of most essential amino acids. We investigated if a modulation of its activity occurred as a result of starvation or after hormonal treatments. We measured amino acid uptake in brush border membrane vesicles (BBMV) purified from the anterior-middle (AM) and posterior (P) regions of the midgut in fifth instar larvae. Silkworms were either starved or topically treated with low dosages of fenoxycarb, a molecule often used as a juvenile hormone mimic. The maximal uptake value of K(+)-driven leucine transport was increased in BBMV of AM- and P-midgut regions of starved larvae. The initial uptake rates of serine and glutamine, two amino acids transported by the same cotransporter as leucine, were also increased. Leucine kinetics proved that V(max) was the kinetic parameter modified by starvation in both midgut regions. Topical applications of fenoxycarb at a dose of 2.5 fg/larva immediately after the fourth ecdysis, induced an increase of leucine initial uptake rates and of intravesicular accumulation of leucine in both AM- and P-BBMV. Kinetic analysis of leucine uptake indicated again that V(max) was increased in BBMV from both midgut regions in treated larvae.     

Effects of ultralow doses of fenoxycarb on juvenile hormone–regulated physiological parameters in the silkworm,Bombyx mori L.

Effects of fenoxycarb at ultralow doses were investigated on juvenile hormone (JH)–regulated parameters in the silkworm, B. mori. Like JH, this non-terpenoid carbamate is able to induce permanent larvae in the last larval instar. However, whereas micrograms of JH are needed to produce this effect, only a few picograms of fenoxycarb are necessary to induce the same effect. The effects of fenoxycarb observed in this study were only visible from day 4 of the last larval instar—that is, when the JH titer has dropped to undetectable levels and JH-repressed physiological parameters would naturally be expressed. We observed that the permanent larvae induced with low doses of fenoxycarb (100 pg/larva) had no 20-hydroxyecdysone (20E) peak. Their prothoracic glands (Pgs) were completely inactive and very weakly sensitive to prothoracicotropic hormone (PTTH). Fenoxycarb at doses of 1 ng/larva also significantly inhibited silk gland growth and coloration, whereas carotenoid content of the hemolymph was maintained at high levels, which could reflect an inhibition of its uptake by the silk glands. Total hemolymph protein levels in last instar larvae were also depressed at these doses. So, it seems that low doses of fenoxycarb are sufficient to maintain in a juvenilized status the physiological parameters that are normally expressed when JH titer has declined. Moreover, from an endocrinological viewpoint, we demonstrated that the corpora allata (CA) are not necessary for fenoxycarb to induce those effects and discussed its possible mode of action. Arch. Insect Biochem. Physiol. 37:178–189, 1998. © 1998 Wiley-Liss, Inc.     

Thyroxine influence on different ion-specific adenosine triphosphatase activities in fat body of Bombyx mori during development

The effects of thyroxine on the activity of different ATPases (Na⁺-K⁺, Ca²⁺, and Mg²⁺) in fat body cells of the silkworm, Bombyx mori, were investigated during different developmental stages. In both sexes the maximum enzyme activity was observed in the fat body cells of day 7 last instar larva (the day before spinning). Na⁺-K⁺, Ca²⁺-, and Mg²⁺-ATPase activity in the fat body markedly declined after pupation and continued to decrease in day 1 adults. Injection of thyroxine (T4) at doses of 1.0 and 2.0 μg/g during fifth instar significantly elevated all ATPase activities in the larval, pupal, and adult stages in both sexes. At a dose of 0.5 μg/g, T4 had no effect on day 2 fifth instar larva, although it increased the ATPase activity at the other stages investigated. A higher dose (3.0 μg/g) caused a significant reduction in enzyme activity in all stages with the exception of day 2 fifth instar larva. Thus, the repression of enzyme activity with the higher dose and the elevation of enzyme activity with the lower dose establish the biphasic nature of T4 action on the ATPase system in fat body cells of the silkworm. Arch. Insect Biochem. Physiol. 37:191–196, 1998. © 1998 Wiley-Liss, Inc.     

Tissue-specific regulation of juvenile hormone esterase gene expression by 20-hydroxyecdysone and juvenile hormone in Bombyx mori

Juvenile hormone esterase (JHE) is the primary juvenile hormone (JH) metabolic enzyme in insects and plays important roles in the regulation of molt and metamorphosis. We investigated its mRNA expression profiles and hormonal control in Bombyx mori larvae. JHE mRNA was expressed at the end of the 4th and 5th (last) larval instars in the midgut and in all the three (anterior, middle, posterior) parts of the silk gland. In the fat body, JHE expression peaked twice in the 5th instar, at wandering and before pupation, while it gradually decreased through the 4th instar. When 20-hydroxyecdysone (20E) was injected into mid-5th instar larvae, JHE mRNA expression was induced in the anterior silk gland but suppressed in the fat body. Topical application of a juvenile hormone analog fenoxycarb to early-5th instar larvae induced JHE expression in both tissues. In the anterior silk gland, JHE expression was accelerated and strengthened by 20E plus fenoxycarb treatments compared with 20E or fenoxycarb single treatment, indicating positive interaction of 20E and JH. JHE mRNA is thus expressed in tissue-specific manners under the control of ecdysteroids and JH.     

Nutrient absorption by Aphidius ervi larvae

It is well documented that in the model system Aphidius ervi Haliday (Hymenoptera, Braconidae)/Acyrthosiphon pisum (Harris) (Homoptera, Aphididae) host regulation by the parasitoid larva induces in the aphid haemolymph major changes of the titer of nutritional compounds such as proteins, acylglycerols and free amino acids, in order to meet the stage-specific demands of the developing larva. Since little is known about how the larva absorbs these mobilized nutritional resources, nutrient absorption by larval stages of A. ervi was studied. In 2nd instar larvae, leucine was ten-fold accumulated in the haemocoel, and tyrosine and glutamine two-fold. Glucose and fructose were readily absorbed and fructose was extensively metabolized by larval tissues. In 3rd instars, the presence of a number of larvae that did not ingest the incubation medium enabled us to determine the respective amounts of substrate absorbed by the epidermis and the midgut. An accumulation of leucine in the haemocoel was observed only when midgut cells were involved in absorption, while the amino acid concentration within body fluids never exceeded that of the incubation medium when the uptake was performed only by epidermal cells. The immunofluorescence analysis, the mutual inhibition exerted on labeled glucose or fructose uptakes by a 100-fold excess of the sugars and the strong inhibition of uptakes induced by 0.2mM cytochalasin B support the expression of facilitative GLUT2-like transporters in the apical and basal cell membranes of midgut epithelial cells. Taken together, these results prove that both midgut and epidermis are involved in nutrient absorption throughout the parasitoid development, that GLUT2 transporters are responsible for glucose and fructose uptakes and that the chemical gradient that favors the passive influx of the two sugars is maintained by their conversion to other substrates.     

Midgut proteinase activities of three keratinolytic larvae,Hofmannophila pseudospretella,Tineola bisselliella,and Anthrenocerus australis,and the effect of proteinase inhibitors on proteolysis

The midgut proteinase activities were characterized from the keratinolytic larvae of two lepidopterans, Hofmannophila pseudospretella (Stainton) (Oecophoridae) and Tineola bisselliella (Hummel) (Tineidae), and one coleopteran, Anthrenocerus australis (Hope) (Dermestidae). The major endopeptidase activities, characterized using specific enzyme inhibitors, were serine proteinases with hydrolytic activity against N-benzoyl-DL-arginine-p-nitroanilide and against N-succinyl-L-alanyl-L-alanyl-L-prolyl-L-leucine-p-nitroanilide. No significant levels of metalloendopeptidase or cysteine endopeptidase activities were detected. Aminopeptidase activity was present in all larvae. The enzyme levels and properties of the two moth larvae were similar to each other and to those of phytophagous lepidopteran larvae but different from those of the beetle larva. Whereas only a limited number of serine proteinase inhibitors inhibited the midgut proteolysis of the lepidopteran larvae, most inhibitors inhibited the midgut proteolysis of the beetle larva. © 1994 Wiley-Liss, Inc.     

Ghrelin effect on nutritional indices, midgut and fat body of Lymantria dispar L. (Lymantriidae)

Ghrelin is a 28-amino acid peptide that has significant effects on appetite and growth in humans and animals. The aim of this study was to examine 4th instar larvae of the pest insect Lymantria dispar L. after ghrelin treatment. Parameters included changes in nutritional indices (efficiency of conversion of ingested food, efficiency of conversion of digested food, approximate digestibility); midgut and fat body mass; total proteases, trypsin and leucine aminopeptidase activities in the midgut; number, height and width of columnar and goblet cells and their nuclei in the midgut epithelium and detection of ghrelin-like immunoreactivity in the midgut tissue. Four subpicomolar injections of ghrelin (0.3pmol) or physiological saline (control) were applied every 24h. The nutritional indices were higher in the ghrelin treated than in the control group. Ghrelin treatment was also associated with elevation of midgut mass, induced digestive enzyme activities, increased fat body mass and morphometric changes in columnar and goblet cells. This is the first report of the presence of ghrelin-like hormone in endocrine cells of an insect midgut. Such information provides additional evidence for application of this relatively simple model system in the future studies of the mechanisms underlying of digestion and energy balance in more complex organisms.     

Characterization and distribution of chymotrypsin-like and other digestive proteases in Colorado potato beetle larvae

Chymotrypsin-like, carboxypeptidase A-like and leucine aminopeptidase-like activities have been detected in the midgut of Colorado potato beetle larvae, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), in addition to the previously identified cathepsin B, D, and H. We have characterized a new chymotrypsin-like activity using the specific substrates N- succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanine-p-nitroanilide and N-benzoyl-L-tyrosine p-nitroanilide. This novel proteinase, with a pH optimum of 5.5–6.5, was neither activated by thiol compounds nor inhibited by cysteine proteinase inhibitors. Among several serine proteinase inhibitors tested, PMSF was the most effective. Gelatin-containing SDS-PAGE gels and activity staining after gel electrophoresis indicated that chymotrypsin-like activity was associated with a major band of about 63 Kda and a minor band of about 100 Kda. The major exopeptidases found in the larval midgut extracts were leucine aminopeptidase and carboxypeptidase A. Most endo- and exoproteolytic activities studied were evenly distributed among the midgut sections, indicating that there is no clear regional differentiation in the digestion of proteins. Chymotrypsin and cathepsin B, D, and H were mainly located in the endoperitrophic and ectoperitrophic spaces, with only a small activity associated with the midgut epithelium. In contrast, leucine aminopeptidase was mainly located on the wall tissue, although some activity was distributed between the ecto- and endoperitrophic spaces. The potential roles of Colorado potato beetle digestive chymotrypsin in the proteolytic activation of the δ-endotoxin from Bacillus thuringiensis, and in the use of protease inhibitors to disrupt protein digestion, are discussed. Arch. Insect Biochem. Physiol. 36:181–201, 1997. © 1997 Wiley-Liss, Inc.     

幼虫密度对草地螟食物利用率及消化酶活性的影响

为了阐明草地螟Loxostege sticticalis大发生种群幼虫取食行为特征, 在室内条件下（温度22±1℃, 相对湿度70%）对不同幼虫密度［1, 10, 30头/瓶（650 mL）］饲养草地螟幼虫的食物利用率及消化酶活性进行了研究。结果表明： 幼虫中等（或高）密度对草地螟幼虫相对中肠重量、 相对取食量、 粪便干重、 食物利用率和近似消化率及总蛋白酶和亮氨酸氨肽酶活性影响显著。幼虫相对中肠重量以10头/瓶的幼虫密度最大, 1头/瓶的幼虫密度最小。随着幼虫密度的增加, 幼虫相对取食量和粪便干重增加, 而虫体干重减轻, 幼虫食物利用率降低。幼虫密度30头/瓶的幼虫相对取食量和粪便干重显著高于1和10头/瓶的, 而30头/瓶的幼虫食物利用率显著低于1头/瓶的。幼虫近似消化率随幼虫密度的逐渐增加而显著降低。幼虫密度10头/瓶的幼虫总蛋白酶和亮氨酸氨肽酶的活性显著高于1和30头/瓶的, 而淀粉酶的活性受幼虫密度影响不显著。随幼虫密度的增加, 幼虫相对中肠重量与总蛋白酶和亮氨酸氨肽酶活性变化趋势较为一致, 消化酶活性的变化可能与相对中肠重量大小有关。因此, 幼虫密度是影响草地螟幼虫取食行为的重要因子, 这些结果为阐明草地螟大发生种群与一般种群的为害特征提供了重要理论依据。     

Digestive proteinases of larvae of the corn earworm, Heliothis zea: characterization, distribution, and dietary relationships.

Proteinases and peptidases from the intestinal tract of fifth-instar larvae of Heliothis (= Helicoverpa) zea (Boddie) (Lepidoptera:Noctuidae) were characterized based on their substrate specificity, tissue of origin, and pH optimum. Activity corresponding to trypsin, chymotrypsin, carboxypeptidases A and B, and leucine aminopeptidase was detected in regurgitated fluids, midgut contents, and midgut wall. High levels of proteinase activity were detected in whole midgut homogenates, with much lower levels being observed in foregut and salivary gland homogenates. In addition, enzyme levels were determined from midgut lumen contents, midgut wall homogenates, and regurgitated fluids. Proteinase activities were highest in the regurgitated fluids and midgut lumen contents, with the exception of leucine aminopeptidase activity, which was found primarily in the midgut wall. Larvae fed their natural diet of soybean leaves had digestive proteinase levels that were similar to those of larvae fed artificial diet. No major differences in midgut proteinase activity were detected between larvae reared under axenic or xenic conditions, indicating that the larvae are capable of digesting proteins in the absence of gut microorganisms. The effect of pH on the activity of each proteinase was studied. The pH optima for the major proteinases were determined to be pH 8.0-8.5 for trypsin, when tosyl-L-arginine methyl ester was used as the substrate; and pH 7.5-8.0 for chymotrypsin, when benzoyl-L-tyrosine ethyl ester was used as the substrate.     

保幼激素类似物苯氧威对异色瓢虫不同发育阶段的影响

【目的】本研究旨在明确保幼激素类似物苯氧威对天敌异色瓢虫Harmonia axyridis的影响, 并探讨其作用机理, 以便进行安全性评价并为科学使用提供理论依据。【方法】应用连叶浸渍法、浸渍法、点滴法和药膜法分别处理异色瓢虫卵、2龄幼虫、蛹和成虫, 观察苯氧威对4个虫态的影响。【结果】用浓度为0.0001 μg/mL的药液处理初产卵, 能抑制胚胎的发育; 但用高达20 000 μg/mL的药液处理发育2 d的卵, 幼虫仍可正常孵化; 用浓度高达4 000 μg/mL的药液浸渍2龄幼虫, 对幼虫的致死作用极小; 用浓度为0.0001 μg/头的药液处理当天蛹, 形成蛹 成虫中间体, 羽化的成虫畸形; 用浓度为0.0125 μg/mL的药液处理成虫, 24 h后成虫的生命力受到明显影响。【结论】苯氧威对异色瓢虫初产卵有明显的毒杀作用, 严重阻碍蛹到成虫的变态和影响成虫的存活。在田间使用该杀虫剂时, 要避开异色瓢虫的敏感期。     

Phenotypic changes and the fate of digestive enzymes during induction of amber disease in larvae of the New Zealand grass grub (Costelytra zealandica)

Amber disease of the New Zealand grass grub Costelytra zealandica (Coleoptera: Scarabaeidae) is caused by ingestion of pADAP plasmid carrying isolates of Serratia entomophila or Serratia proteamaculans (Enterobacteriaceae) and causes infected larvae to cease feeding and clear their midgut to a pale amber colour where midgut serine protease activities are virtually eliminated. Using bacterial strains and mutants expressing combinations of the anti-feeding (afp) and gut clearance (sep) gene clusters from pADAP, we manipulated the disease phenotype and demonstrated directly the relationship between gene clusters, phenotype and loss of enzyme activity. Treatment with afp-expressing strains caused cessation of feeding without gut clearance where midgut protease activity was maintained at levels similar to that of healthy larvae. Treatment with strains expressing sep-genes caused gut clearance followed by a virtual elimination of trypsin and chymotrypsin titre in the midgut indicating both the loss of pre-existing enzyme from the lumen and a failure to replenish enzyme levels in this region by secretion from the epithelium. Monitoring of enzymatic activity through the alimentary tract during expression of disease showed that loss of serine protease activity in the midgut was matched by a surge of protease activity in the hindgut and frass pellets, indicating a flushing and elimination of the midgut contents. The blocking of enzyme secretion through amber disease appears to be selective as leucine aminopeptidase and α-amylase were still detected in the midgut of diseased larvae.     

Normal and cocoon-forming peritrophic membrane in larvae of the beetle Gibbium psylloides

Larvae of Gibbium psylloides secrete a peritrophic membrane (PM) which has a mainly orthogonal fibrillar structure, but this merges freely with hexagonal and random arrangements of microfibres. The random arrangement predominates in PM used for cocoons. Shortly before the cocoon is constructed the PM no longer forms a tube but collapses and is compressed in the gut and emerges from the anus as a flat thread. This thread is wound around the larva and forms the cocoon ‘silk’. Both normal and cocoon-forming PMs are produced mainly in the posterior midgut and their constituent microfibres appear first at the tips of the microvilli which form the brush border of the midgut cells.     

琥珀蚕丝腺转录因子基因AaSGF-1的克隆、原核表达及组织表达分析

[目的]本研究旨在克隆琥珀蚕Antheraea assama丝腺转录因子基因AaSGF-1,分析其序列特征及表达模式并制备多克隆抗体,为探讨该基因的生理功能奠定基础.[方法]采用RT-PCR和RACE技术从琥珀蚕丝腺中克隆AaSGF-1的cDNA序列,并进行生物信息学分析;利用qPCR检测AaSGF-1在琥珀蚕5龄第4...     

Response of late-instar Blattella germanica (Dictyoptera: Blattellidae) to dietary insect growth regulators

Late-instar German cockroaches, Blattella germanica (L.), were used to evaluate the relative effects of single treatments and combinations of three insect growth regulators (IGRs): pyriproxyfen, fenoxycarb, and diflubenzuron. Groups of 15 males or 15 females were held for 2 wk on food treated with varying amounts of IGRs. After removal, newly mature adults were placed with untreated adults of the opposite sex. Mortality, adult phenotype (normal wings, divergent wings, curly wings, and nymphoids), and reproduction were assessed. Mortality occurred largely in the nymphal stage except when all three IGRs were combined. Neither the average number of nymphs per egg case nor hatch of egg cases from phenotypically normal cockroaches (normal wings, occasional darkening of the body) was affected in single treatments or in combinations of two IGRs, but nymphal numbers were reduced when the three IGRs were combined. Hatch from matings of insects with divergent wings varied. At low concentrations (3-10 ppm), hatch was generally normal; at high concentrations, most mating tests were unproductive. Mating tests of cockroaches with curly wings were almost always unproductive. When males with curly wings were mated, females dropped either unfertilized egg cases (no mating) or partially fertilized egg cases. Curly-wing females either dropped unfertilized egg cases or failed to form egg cases because of deleterious effects on ovarian development. Nymphoids did not mate. Diflubenzuron at 100 ppm had no effect other than causing the appearance of a few insects with divergent wings. Effects on phenotype and reproduction began at 3 ppm of both pyriproxyfen and fenoxycarb and at a comparable concentration in the combination of pyriproxyfen + fenoxycarb (1 ppm each). Female sterility was complete at 100 ppm of pyriproxyfen and fenoxycarb. When pyriproxyfen or fenoxycarb was combined with equal amounts of diflubenzuron, the number of productive matings was not reduced at 6 ppm (3 ppm per each IGR). At 20 ppm (10 ppm per each IGR), a reduction in productive matings coincided with the appearance of curly wings. Complete female sterility occurred only at 600 ppm (300 ppm per IGR). The most severe effects occurred in the experiment with equal amounts of pyriproxyfen, fenoxycarb, and diflubenzuron. In addition to reduced hatch from normal phenotypes, this experiment caused complete male sterility (300 ppm; 100 ppm of each IGR). Female sterility was complete at greater than or equal to 90 ppm (30 ppm of each IGR).     

Insect resistance to Bacillus thuringiensis: alterations in the indianmeal moth larval gut proteome

Insect resistance to the Cry toxins of Bacillus thuringiensis (Bt) has been examined previously using a number of traditional biochemical and molecular techniques. In this study, we utilized a proteomic approach involving two-dimensional differential gel electrophoresis, mass spectrometry, and function-based activity profiling to examine changes in the gut proteins from the larvae of an Indianmeal moth (IMM, Plodia interpunctella) colony exhibiting resistance to Bt. We found a number of changes in the levels of certain specific midgut proteins that indicate increased glutathione utilization, elevation in oxidative metabolism, and differential maintenance of energy balance within the midgut epithelial cells of the Bt-resistant IMM larva. Additionally, the electrophoretic migration pattern of a low molecular mass acidic protein, which apparently is an ortholog of F(1)F(0)-ATPase, was considerably altered in the Bt-resistant insect indicating that variations in amino acid content or modifications of certain proteins also are important components of the resistance phenomenon in the IMM. Furthermore, there was a dramatic decrease in the level of chymotrypsin-like proteinase in the midgut of the Bt-resistant larva, signifying that reduction of chymotrypsin activity, and subsequently decreased activation of Cry toxin in the insect midgut, is an important factor in the resistant state of the IMM. The proteomic analysis of larval gut proteins utilized in this study provides a useful approach for consolidating protein changes and physiological events associated with insect resistance to Bt. Our results support the hypothesis that physiological adaptation of insects and resistance to Bt is multifaceted, including protein modification and changes in the synthesis of specific larval gut proteins. We believe that increased oxidative metabolism may be an adaptive response of insects that undergo survival challenge and that it could mediate detoxification as well as higher rates of generalized and localized mutations that enhance their resistance and provide survival advantage.     

D‐3‐phosphoglycerate dehydrogenase from the silkworm Bombyx mori: Identification,functional characterization,and expression

D‐3‐phosphoglycerate dehydrogenase (PHGDH) is a key enzyme involved in the synthesis of l ‐serine. Despite the high serine content in silk proteins and the crucial role of PHGDH in serine biosynthesis, PHGDH has not been described in silkworms to date. Here, we identified PHGDH in the silkworm Bombyx mori and evaluated its biochemical properties. On the basis of the amino acid sequence and phylogenetic tree, this PHGDH has been categorized as a new type and designated as bmPHGDH. The recombinant bmPHGDH was overexpressed and purified to homogeneity. Kinetic studies revealed that PHGDH uses NADH as a coenzyme to reduce phosphohydroxypyruvate. High expression levels of bmphgdh messenger RNA (mRNA) were observed in the middle part of the silk gland and midgut in a standard strain of silkworm. Moreover, a sericin‐deficient silkworm strain displayed reduced expression of bmphgdh mRNA. These findings indicate that bmPHGDH might play a crucial role in the provision of l ‐serine in the larva of B. mori.     

Acute dieldrin toxicity: effect on the uptake of glucose and leucine and on brush border enzymes in monkey intestine

Administration of a single oral dose of dieldrin (20 mg/kg body wt.) to rhesus monkeys considerably elevated the uptake of glucose and the activities of brush border sucrase, lactase, maltase and alkaline phosphatase in intestine compared to control animals. Leucine uptake and leucine amino peptidase activity was significantly depressed in pesticide-treated animals. Kinetic studies with brush border sucrase revealed that augmentation of enzyme activity in pesticide-fed animals was due to an increase in the disaccharidase content.     

Uptake of cholesterol and cholestanol by the intestine,hemolymph, and fat body of Heliothis zea

The effect of the concentration and structure of dietary sterol on its uptake and distribution in the intestine, hemolymph and fat body was studied in sixth-instar larvae of Heliothis zea. When cholesterol (cholest-5-en-3β-ol) was inoculated per os into the foregut of larvae, it was rapidly taken up by the intestine. Some of the dietary sterol then passed into the hemolymph, primarily via the midgut, during at least the first 9 h after inoculation, while at least 7% of the dose remained associated with the intestine. The amount of dietary sterol per 0.10 g of hemolymph increased until it reached 3–6% of the dose after 9 h. The amount of sterol per 0.10 g of the fat body increased to as much as 5% of the dose after 10 h. As the concentration of sterol in the dose increased from 0.3 to 15 μg/4 μl, the amount of sterol associated with the intestine, hemolymph, and fat body also increased. When cholesterol was inoculated intrahemocoelically, instead of per os, the amount of sterol in the hemolymph decreased, for at least the first 8 h after inoculation, and may have been absorbed, at least in part, by the intestine. The absence of a double bond in cholestanol (5α-cholestan-3β-ol) had no significant effect, at least 5 h after inoculation, on the uptake and distribution of this sterol in the intestine, hemolymph, and fat body of the larva. The results of this study indicate that although larvae of H. zea fed cholestanol have a slower rate of growth than those fed cholesterol, this may be due to differences in the utilization of the two sterols rather than to differences in their uptake by the tissues.