Ecdysial failures in the cotton boll weevil: Synergism of diflubenzuron with juvenile hormone

The frequency and etiology of ecdysial failures occurring during the pupal-adult transformation of the cotton boll weevil, Anthonomus grandis, was studied after treatment with juvenile hormone (JH) and/or diflubenzuron (DFB). Failure at emergence was the result of inability of the adult insects to escape from their pupal exuviae. Teratogenic effects in the form of pupal-adult intermediates or adults with pupal characters were not obtained with JH or DFB treatment after the larval-pupal ecdysis. Combining JH with the DFB treatment yielded a synergistic response that increased the frequency of ecdysial failures about sevenfold when applied in the later pupal stages. The fine structure of the abdominal cuticle of adults experiencing ecdysial failure after treatment with JH as white-eyed pupae exhibited granular deposits within the lamellar region and interference with deposition of the nonlamellate endocuticle. DFB treatment of the earlier pupal stages interfered with deposition of the lamellate cuticle by eliminating or reducing the lamellar structure. It was concluded that the primary interaction of JH with DFB was that of extending or reinitiating DFB sensitivity in the later pharate adult. A secondary interaction may involve inhibition of cuticle hardening as both JH and DFB appear to inhibit the tanning process of adults treated as white-eyed pupae.     

Effects of diflubenzuron on the pupal-adult development of Tenebrio molitor L. (Coleoptera,Tenebrionidae): Growth and development,cuticle secretion,epidermal cell density,and DNA synthesis

Diflubenzuron (DFB), applied by dipping on newly emerged pupae of Tenebrio molitor L., disturbs the pupal-adult development. Four main types of treated insects were obtained according to external morphology: blocked pupae, adults unable to ecdyse, adults partially ecdysed, and adults completely ecdysed. The proportion of these four types varied with the time of treatment during the pupal life. When DFB was administered by dipping at a 10 g/liter concentration to newly emerged pupae, HPLC measurements showed that the different responses were due to a difference in the levels actually incorporated. Histological and ultrastructural observations of sternal cuticles revealed that DFB disturbs the cuticle deposition: reduction of its thickness and modifications of its architecture. Tritiated thymidine incorporation and cell density measurements in sternal epidermis show that DFB affects both mitoses and DNA synthesis in blocked pupae. These findings suggest that DFB interferes with other biochemical processes besides the chitin biosynthesis; whether these effects are primary or secondary remain to be determined.     

Effects of diflubenzuron on the integument of fifth instar<Emphasis Type="Italic">Galleria mellonella</Emphasis> larvae

Effects of the chitin synthesis inhibitor diflubenzuron (DFB) on the integument of 5th instarGalleria mellonella L. larvae were investigated. When larvae were fed with semi-artificial diets containing 250, 500 and 1000 ppm of the compound, DFB affected the integument. The affected larvae failed to ecdysis, their cuticle was ruptured, lost haemolymph and blackened. In treated larvae, cuticle deposition was disrupted and the cuticle thickness was decreased by ∼50% compared with the untreated control, particularly at day 3 1/2. However, statistically there was no significant difference among the three concentrations (P>0.05). This may indicate that all three concentrations are equally effective in decreasing level. DFB at 500 and 1000 ppm also affected the epidermal cells and caused the occurrence of vacuoles. http://www.phytoparasitica.org posting Dec. 16, 2003.     

Cuticular penetration of β-cypermethrin in insecticide-susceptible and resistant strains of Bactrocera dorsalis

Semi-thin sectioning and transmission electron microscope techniques were employed to investigate the cuticle thickness, integument structure, and fat body of larvae from susceptible and resistant strains of Bactrocera dorsalis. The results showed that the cuticle of β-cypermethrin-resistant strains (25.96 ± 1.00 μm) was thicker than that of susceptible strains (19.36 ± 0.82 μm). The number of chitin layers in the endocuticle of β-cypermethrin-resistant strains (98.00 ± 3.61 layers) was more than that in susceptible strains (75.67 ± 2.40 layers). Compared with susceptible strains, the laminated structure of the chitin layers in the endocuticle of resistant strains revealed higher density and more distinctive structure, and the interspace of epidermal cells was thicker. Fat body in the resistant insects contained more fat granules than those in susceptible insects. Moreover, HPLC analysis showed that the cuticular penetration of β-cypermethrin into larvae of resistant strains was slower than that of susceptible strains. In addition, the metabolism of β-cypermethrin in resistant strains was faster than that in susceptible strains, indicating that the resistant strains could enhance detoxification metabolism. These results indicated that cuticle thickness, fat body, laminated structure of the chitin layers, and interspace of epidermal cells might be correlated with cuticular penetration between susceptible and resistant strains, suggesting that the resistant strains could decrease the rate of penetration of insecticide into the internal cavity.     

Studies on the action mechanism of benzoylurea insecticides to inhibit the process of chitin synthesis in insects: A review on the status of research activities in the past, the present and the future prospects

In this review an effort was made to summarize the up to date information on the knowledge on the action mechanism of diflubenzuron (DFB), a prototype chemical for the benzoylurea type insecticides, with respect to its molecular mechanism to inhibit insect chitin synthesis. The key problem in pinpointing the action site of this insecticide has been the lack of in vitro demonstration of its action to inhibit insect chitin synthesis under cell free conditions. This problem was solved when an approach using a intracellular vesicle preparation from the cuticle of newly molted Periplaneta americana was developed. Using this approach it has become possible to identify that DFB indeed inhibits the process of incorporation of N-acetylglucosamine into insect chitin. Recently there has been a breakthrough in this field, when a sulfonylurea receptor (SUR) was identified in Drosophila melanogaster. This information was instrumental in establishing that insect SUR in the above intracellular vesicular preparation from P. americana as well as Blattella germanica is likely the actual target site of DFB to cause inhibition of chitin synthesis. The role of SUR in this case has been determined, by using glibenclamide, a typical SUR specific inhibitor as an aid, to be helping the exocytotic movement of these vesicles as is the case of other members of the group of ABC-transporters to which insect SUR belongs. In this case both DFB and glibenclamide have been shown to cause the depolarization of the vesicle membrane through inhibition of the K⁺ channel, which leads to their inhibition of chitin synthesis.     

The cuticle,growth and moulting in insects: The essential background to the action of acylurea insecticides

The functions, structure and biochemistry of the insect cuticle in relation to the moulting cycle are briefly reviewed as an introduction to the actions of insecticides that act on the cuticle, particularly acylureas. The symptoms of poisoning with diflubenzuron (DFB) and other acylureas are consistent with ultra-structural and biochemical evidence that these insecticides inhibit the formation of chitin microfibrils in newly synthesised cuticle. It is probable that DFB acts at a late stage in chitin biosynthesis, perhaps inhibiting chitin synthase (CS) itself. However, the results of studies using cell-free preparations of CS have not, on the whole, supported this hypothesis. A number of alternative suggestions as to the mode of action of DFB are reviewed. Among the most attractive of these is the possibility that DFB may inhibit the transmembrane transport of chitin synthesis precursors from their site of production within the epidermal cells to the site of the final poly condensation reaction, presumably at the apical membrane of the epidermal microvilli.     

Ph 70–23: A new acaricide and insecticide interfering with chitin deposition

PH 70–23 is a new benzoylphenylurea interfering with chitin deposition. In larvae of Spodoptera littoralis, incorporation of N-acetyl-glucosamine into chitin was equally inhibited by PH 70–23 and diflubenzuron, the first commercially available benzoylphenylurea. In contrast to diflubenzuron, which is active only against insects and eriophyid mites, PH 70–23 has the advantage of also being highly active on spider mites. The latter activity might be partly due to leaf penetration of PH 70–23. Laboratory experiments indicate PH 70–23 to have a better ovo-larvicidal activity than the commercial acaricides tested (cyhexatin, dicofol, fenbutatin oxide and tetradifon) against Tetranychus cinnabarinus, T. turkestani, T. urticae and Panonychus ulmi. A method in which eggs were deposited on residues of cyhexatin or fenbutatin oxide resulted in much lower activities than application of the spray liquid after egg deposition. Activities of PH 70–23, dicofol and tetradifon were hardly influenced by this difference in the test method. The direct contact activity of PH 70–23 on eggs of mites is influenced by the relative humidity and the age of the eggs. The total ovolarvicidal activity of PH 70–23 is only slightly positively influenced by the relative humidity, however. Ovicidal activity of PH 70–23 is also achieved by transovarial transmission. The compound does not influence the fertility of the mites. Comparison of a strain of T. urticae, resistant to dicofol, parathion and tetradifon, with a susceptible strain indicated absence of cross-resistance to PH 70–23. Compared to diflubenzuron, PH 70–23 shows an interesting shift in the spectrum of insecticidal activity.     

棉铃虫表皮蛋白基因CP22和CP14的表达特征及其对甲氧虫酰肼的响应

为揭示棉铃虫Helicoverpa armigera表皮蛋白（cuticular protein，CP）基因在其生长发育及应对药剂胁迫中的作用，克隆棉铃虫2个CP基因CP22和CP14，利用实时荧光定量PCR技术分析其在不同发育阶段和不同组织中的相对表达量，并于显微镜下观察甲氧虫酰肼亚致死剂量处理后棉铃虫3龄幼虫的表皮形态，并用实时荧光定量PCR技术测定药后CP22和CP14基因的相对表达量。结果显示，CP22和CP14的开放阅读框全长分别为570 bp和393 bp，分别编码189个和130个氨基酸；CP22和CP14都具有1个几丁质结合域，属于CPR家族RR-1亚类；CP22和CP14基因均在棉铃虫5龄幼虫表皮中表达水平高；这2个基因在棉铃虫幼虫期的表达水平高于在卵期、蛹期和成虫期的表达水平，且在4龄幼虫体内表达量最高，在蜕皮后随着日龄的增加表达量逐渐降低；甲氧虫酰肼处理后棉铃虫3龄幼虫表皮黑化、皱缩，发生蜕皮异常，显微观察显示其内外表皮分离，真皮细胞解体；甲氧虫酰肼处理后24 h和48 h，棉铃虫CP22和CP14基因的相对表达量显著上调。表明棉铃虫CP22和CP14基因参与棉铃虫幼虫蜕皮，并且响应甲氧虫酰肼胁迫，可作为防治棉铃虫的潜在靶标基因。     

Dietary TH 6040 alters composition and enzyme activity of housefly larval cuticle

Housefly larvae of 2 days of age were allowed to grow in media containing 0, 0.4, 1.0, or 2.5 ppm TH 6040[1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea] for 3 days prior to analysis of the cuticle for structural components (chitin and protein) or enzymes important in cuticle formation (chitinase and phenoloxidase). As the TH 6040 concentration is increased, the amount of chitin is progressively reduced such that, at 2.5 ppm TH 6040, the level is only 25% of normal. The amount of cuticle protein is unaffected so the protein: chitin ratio increases from 3.4 in the control larvae to 14.3 in 2.5 ppm-treated larvae, an alteration which probably affects the elasticity and firmness of the endocuticle. Dietary TH 6040 at 1.0 ppm increases the cuticle chitinase activity to about 180% and the cuticle phenoloxidase activity to 155% as compared with control larvae, with a further chitinase activity increase to 240% of normal at 2.5 ppm TH 6040. These enzyme changes are expected to hamper the build-up or maintenance of the cuticle chitin and enhance sclerotization of the exocuticle.     

Insecticidal action of mammalian galectin‐1 against diamondback moth (Plutella xylostella)

BACKGROUND: Previous studies showed that mammalian galectin‐1 (GAL1) could interact with chitosan or chitin, one component of the peritrophic membrane (PM). This finding suggests that the PM could be a target of GAL1, which prompted the authors to explore the effect of GAL1 on larval growth and its potential mechanism. RESULTS: The development of Plutella xylostella (L.) larvae was significantly disturbed after they were fed recombinant GAL1. The histochemical structure and immunostaining pattern suggested that GAL1 treatment resulted in dose‐ and time‐dependent disruption of the microvilli and abnormalities in these epithelial cells. Ultrastructural studies showed that the PM was not present in the midgut of GAL1‐treated insects; instead, numerous bacteria were found in the lumen area. These results indicate that the protective function of the PM was disrupted by GAL1 treatment. Moreover, in vitro data showed that GAL1 interacts with chitosan/chitin in a dose‐dependent manner, and also specifically binds to the PM in vitro. CONCLUSION: In view of the fact that the carbohydrate recognition domain of GAL1 recognises the structural motif N‐acetyl lactosamine (Gal β 1–4 GlcNAc), which is similar to that of chitin (β‐1,4 N‐acetyl‐D ‐glucosamine), it is proposed that the insecticidal mechanism of GAL1 involves direct binding with chitin to interfere with the structure of the PM. Copyright © 2009 Society of Chemical Industry     

The inhibition of chitin synthesis in spodoptera littoralis larvae by flufenoxuron,teflubenzuron and diflubenzuron

The chitin precursor [¹⁴C] N-acetylglucosamine injected into the haemolymph of Spodoptera littoralis (Boisduval) larva was incorporated into the chitin exponentially with time. When caterpillars were injected with precursor at the commencement of feeding on acylurea-treated leaf discs, flufenoxuron, teflubenzuron and diflubenzuron were found to be equally effective inhibitors of chitin synthesis, measured after 21 h. The dose response curves by feeding are not parallel, indicating that the relative potency of the compounds will vary across the dose range. When chitin precursor was injected simultaneously with topically applied diflubenzuron, flufenoxuron or teflubenzuron, all three acylureas were found to be equally effective as inhibitors of chitin synthesis when measured after five hours. The I₅₀values (50% inhibition of chitin synthesis) were not significantly different; average 600 ng, compared with LD₅₀values (50% lethal dose) of ～ 13 ng for flufenoxuron and teflubenzuron but 130 ng for diflubenzuron (topical application). Injection of precursor 24 h after topical application of insecticide gave an I₅₀value which had dropped 670- and 150-fold for flufenoxuron and teflubenzuron respectively but only 20-fold for diflubenzuron. It is postulated that the reason for the low increase in diflubenzuron effectiveness with time was due either to less diflubenzuron than flufenoxuron reaching the site of action, or more probably, a faster rate of metabolism and excretion for diflubenzuron. The lower toxicity of diflubenzuron compared with flufenoxuron and teflubenzuron may not be due to any inherent differences in biochemical effectiveness, but rather to different penetration/metabolism properties.     

Temperature effects on the action of acylurea insecticides against tobacco hornworm (Manduca sexta) larvae

The toxic effects of six acylurea insecticides on larvae of the tobacco hornworm were investigated at each of four environmental temperatures (20, 25, 30 and 35°C). This spans the range of temperatures which the insects can tolerate. For all the acylureas tested, mortality increased with temperature when either newly hatched or fourth-instar larvae were given insecticide in their food. Sub-lethal growth inhibition also became more pronounced at progressively higher environmental temperatures. This temperature dependence of acylurea action was not due to altered uptake of the insecticide, since there was no significant variation with temperature in the amount of [¹⁴C]flufenoxuron taken up by fifth-instar larvae when given a single meal containing labelled insecticide. Additionally, mortality of fourth-instar larvae given a single intra-haemocoelic injection of flufenoxuron was significantly greater at higher temperatures, implying that temperature affects a process that occurs after insecticide uptake. The intrinsic ability of acylureas to inhibit chitin synthesis is temperaturesensitive, since flufenoxuron inhibited the incorporation of [¹⁴C]N-acetylalucosamine into chitin by proleg epidermis in vitro significantly less well at 20°C than at the higher temperatures tested. However, there was no significant variation between the effectiveness of in-vitro chitin synthesis inhibition at 25, 30 and 35°C. These data show that the effectiveness of acylurea insecticides is subject to strong temperature effects in the range of temperatures likely to be experienced in the field.     

The effects of diflubenzuron on the growth of insect cuticle

Cuticle consists of chitin microfibrils embedded in a matrix composed largely of hydrated proteins. The effect of diflubenzuron, an inhibitor of chitin synthetase, on the deposition of both these components is reviewed. The polymerisation reaction is but one step in the pathway leading to chitin microfibrils. Possibly interactions to other steps in the pathway serve to enhance the consequences of the inhibition. Such enhancement could help to explain the abrupt changes in the rate of chitin synthesis that can be observed as diflubenzuron is cleared from epidermal cells. Cuticle proteins differ widely in their ability to form a stable layer when chitin is largely absent. In the most stable regions, diflubenzuron has no effect on the amount or nature of the proteins deposited. In contrast, there are many regions where the deposition of solid cuticle is stopped, presumably because the proteins involved cannot form a coherent layer. Intermediate degrees of stability are found. There is an association between the regions of stability and those of high sclerotisation; though sclerotisation often takes place long after deposition. Even when the protein layer is fairly stable it may not be deposited in a regular manner. This statement is illustrated by electron micrographs of cuticle from the hind tibiae of adult locusts. These micrographs also show that diflubenzuron can affect epidermal cells. In normal cells the plaques are in contact with the newly secreted cuticle; they are still present but this contact is not maintained after treatment with diflubenzuron.     

1-(2,6-disubstituted benzoyl)-3-phenylurea insecticides: Inhibitors of chitin synthesis

The mode of action has been investigated of the 1-(2,6-dichlorobenzoyl)-3-phenyl ureas, a new type of insecticide. A microautoradiographical study was made of the incorporation of glucose, tyrosine, and proline in endocuticle of fifth-instar larvae of Pieris brassicae L., both normal and treated with 1-(2,6-dichlorobenzoyl)-3-(3,4-dichlorophenyl)-urea (DU 19111). The results of this work clearly indicate that DU 19111 blocks the synthesis of cuticular chitin. The nature of this inhibition was investigated by comparison of the rates of incorporation of [¹⁴C]glucose into the ultimate chitin precursor, uridine diphosphate N-acetyl glucosamine (UDPAG), in both normal and DU 19111-treated Pieris larvae. It was found that these levels did not differ significantly.The finding that only in DU 19111-treated Pieris larvae were substantial amounts of labeled N-acetyl glucosamine present 1 hr after the injection of [¹⁴C]glucose is considered as a clue to the mechanism by which this insecticide inhibits chitin synthesis. Apparently the coupling of UDPAG to the chitin synthetase still proceeds, but the function of connecting N-acetyl glucosamine moieties to the chitin chain is disrupted.Tentative results with a structural analog of DU 19111 suggest that this compound induces accumulation of UDPAG, but not of N-acetyl glucosamine. This would imply that in the latter case the polycondensing enzyme is completely blocked.     

Inhibition of chitin synthesis by two 1-(2,6-disubstituted benzoyl)-3-phenylurea insecticides. II

The knowledge of the biochemical mode of action of 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea (diflubenzuron) is presented, explaining the insecticidal effect. Like its structural analog, 1-(2,6-dichlorobenzyl)-3-(3,4-dichlorophenyl)urea (Du 19111), it inhibits chitin synthesis in the cuticle of larvae. Virtually complete inhibition was demonstrable 15 min after the application of diflubenzuron. Neither diflubenzuron nor Du 19111 has any effect upon chitinase activity either in vivo or in vitro. The insecticidal effect upon the cuticle, therefore, must be explained as an inhibition of chitin synthesis and not as an activation of chitin degradation. In contrast to the action of Du 19111, no accumulation of N-acetylglucosamine occurs upon treatment of larvae with diflubenzuron. Similarities and differences in the mode of action of both compounds are discussed, together with other effects reported in the literature.     

Uptake and distribution of three insect growth regulators — diflubenzuron, flucycloxuron and halofenozide — in pupae and adults ofTenebrio molitor

In a topical bioassay with pupae and adults of the mealwormTenebrio molitor (Coleoptera: Tenebrionidae), an important pest in stored products worldwide, three insect growth inhibitors (IGRs) were tested: the two chitin synthesis inhibitors diflubenzuron and flucycloxuron, and the ecdysone agonist halofenozide (RH-0345). To address differences in toxicity, we determined with the use of a¹⁴C-labeled isotope, the pattern of absorption through the cuticle and then the distribution in the different body tissues of gut, hemolymph, integument and reproductive organs (ovaries, testis). The rate of absorption through the cuticle was highest for flucycloxuron, and this concurred with its high toxicity. In general, the patterns of absorption followed a similar trend in young and old pupae and in the adult stage. Accumulation in the reproductive system of females and males was relatively high, which may explain the strong reproductive effects of the IGRs tested. In addition, we recorded large differences in the clearance of insecticide from the insect bodyvia the excrements, with the chitin synthesis inhibitors exhibiting higher rates than halofenozide.     

Quantitative structure—activity studies of insect growth regulators. XI. Stimulation and inhibition of N-acetylglucosamine incorporation in a cultured integument system by substituted N-tert-butyl-N,N′-dibenzoylhydrazines

The ability to stimulate N-acetylglucosamine (GluNAc) incorporation in-vitro of a number of N-tert-butyl-N,N′-dibenzoylhydrazines having various substituents on both phenyl rings was measured in cultured integument excised from the rice stem borer (Chilo suppressalis Walker). The relationship between in-vitro and larvicidal potency was approximately linear. The substituent effects on variations in the potency were similar between in-vitro and larvicidal activities. An inhibitor of oxidative detoxication, piperonyl butoxide, had no synergistic effects on the in-vitro potency. The ability of some dibenzoylhydrazines to inhibit GluNAc incorporation at exposure periods longer than the optimum for stimulation was also measured in a similar cultured integument system. The relationship between the inhibitory and stimulatory potency indices was linear, indicating that the larvicidal activity of dibenzoylhydrazines is closely related to its ability to stimulate as well as to inhibit GluNAc incorporation into the larval cuticle.     

Mode of action of insect growth regulators in lepidopteran tissue culture

Insect growth regulators (IGRs) have been proposed as agents for the control of insect pests. These compounds disrupt the normal development of insects by mimicking juvenile hormone and the molting hormone, 20-hydroxyecdsyone, or by interfering with chitin synthesis. The effectiveness and selectivity of IGRs provide new tools for integrated pest management. The simultaneous advances in the chemistry of IGRs and the ability to study insect tissues in culture, have led to research on the mode of action of IGRs in vitro. Plodia interpunctella and Spodoptera frugiperda have been used to examine the effects of IGRs on wing imaginal discs in organ culture, as well as in hormonally responsive cell lines established from wing imaginal discs of these species. Our research has focused on the action of ecdysteroid mimics, chitin synthesis inhibitors and juvenile hormone mimics. The effects of the IGRs on chitin synthesis, uptake of amino-sugars, and cellular proliferation were studied in tissue culture. The results demonstrate the effectiveness of using organ cultures and hormonally responsive cell lines for investigating IGRs at the cellular and tissue level. © 1998 Society of Chemical Industry     

Wirkungsweise amorpher Diatomeenerden auf vorratssch?dliche Insekten. Untersuchung der abrasiven sowie sorptiven Effekte

The present study examined the morphological and physiological effects of amorphous diatomaceous earth against the stored product pestsS. granarius, T. molitor andT. confusum. Diatomaceous earth, namely Fossil Shield^? and Dryacide^? increased the mortality rate of this insects. After contact with Fossil Shield^? the individuals ofS. granarius had significant lost of weight and reduced their water content respectively. This showed that silica dusts break the water barrier of the cuticle. However, it increases the transpiration rate of water across the cuticle and the insect died past several times through dehydration. As well, an addition of food affected the effectiveness of dusts against insects. A lot of stored product beetles will be able to produce metabolic water of feed substrates. This ability protects and weaves contrary to the loss of water. Diatomaceous earth’s can be effective primarily through the sorptive properties of the hygroscopic particles. One day after dust treatment a significant weight loss ofT. molitor pupae was recorded. The exposure to the silica dust Fossil Shield^? caused partly an incomplete metamorphosis and death of the individuals. Pupae dipped in Fossil Shield^? or abrasive aluminium dust and rolled for further five minutes, reduced not significant higher their weight as unrolled exuvial stages. The morphological analyses of treated insects under the Scanning Electron Microscope showed, that the dust covered the hole integument. Partly, the silica particles sunk into the cuticle. After application of Fossil Shield^? at the cuticle of adults,T. molitor, did not show any wax layer. Also it could not be found once blocked by stigma of the mealworm. The dust particles accumulated around the respiration openings and they partly overgrew.      

Wirkungsweise amorpher Diatomeenerden auf vorratssch?dliche Insekten. Untersuchung der abrasiven sowie sorptiven Effekte

The present study examined the morphological and physiological effects of amorphous diatomaceous earth against the stored product pestsS. granarius, T. molitor andT. confusum. Diatomaceous earth, namely Fossil Shield^? and Dryacide^? increased the mortality rate of this insects. After contact with Fossil Shield^? the individuals ofS. granarius had significant lost of weight and reduced their water content respectively. This showed that silica dusts break the water barrier of the cuticle. However, it increases the transpiration rate of water across the cuticle and the insect died past several times through dehydration. As well, an addition of food affected the effectiveness of dusts against insects. A lot of stored product beetles will be able to produce metabolic water of feed substrates. This ability protects and weaves contrary to the loss of water. Diatomaceous earth’s can be effective primarily through the sorptive properties of the hygroscopic particles. One day after dust treatment a significant weight loss ofT. molitor pupae was recorded. The exposure to the silica dust Fossil Shield^? caused partly an incomplete metamorphosis and death of the individuals. Pupae dipped in Fossil Shield^? or abrasive aluminium dust and rolled for further five minutes, reduced not significant higher their weight as unrolled exuvial stages. The morphological analyses of treated insects under the Scanning Electron Microscope showed, that the dust covered the hole integument. Partly, the silica particles sunk into the cuticle. After application of Fossil Shield^? at the cuticle of adults,T. molitor, did not show any wax layer. Also it could not be found once blocked by stigma of the mealworm. The dust particles accumulated around the respiration openings and they partly overgrew.