Development and encapsulation of the endoparasitoid,Microplitis croceipes (Hym.: Braconidae), in six candidate host species (Lep.)

Encapsulation and development of the endoparasitoid,Microplitis croceipes (Cresson), were studied in six atypical lepidopteran host species whose usual host isHelicoverpa zea (Boddie). The candidate hosts examined were: the fall armywormSpodoptera frugiperda (J. E. Smith); the beet armyworm,Spodoptera exigua (Hübner); the cabbage looper,Trichoplusia ni (Hübner); the greater wax moth,Galleria mellonella (L.); the Indian meal moth,Plodia interpunctella (Hübner); and the diamondback moth,Plutella xylostella (L.). BothS. exigua andT. ni were completely unsuitable forM. croceipes development due to the high rate of eggs that were encapsulated within three days after parasitism. Encapsulation inS. frugiperda included mainly parasitoid eggs and was first detected six days after parasitization at 25°C and two days at 30°C. Encapsulation inG. mellonella occurred only in the larval stage of the parasitoid. InP. interpunctella, parasitoid larvae reached the 3rd stadium, but none of them pupated. OnlyS. frugiperda andG. mellonella supported successful development ofM. croceipes from egg to adult. The percentage of parasitoids reaching the adult stage in these hosts was higher at 30°C than at 25°C (13% vs. 4% inS. frugiperda, and 21% vs. 3% inG. mellonella, respectively). However, these percentages were too low to substitute them as a more economical host for rearingM. croceipes. This biological information will be useful in additional laboratory studies directed toward reducing the rate of encapsulation (e.g., manipulation of host rearing temperature) to increase production ofM. croceipes on these hosts.     

Der Einfluss des Wirtes in der Massenzucht auf die Qualität des EiparasitenTrichogramma evanescens bei der Bekämpfung des Maiszünslers,Ostrinia nubilalis

Zusammenfassung In vier Feldversuchen wurde die Wirksamkeit eines an den Maiszünsler besonders angepassten Stammes vonTrichogramma evanescens Westw. bei der Bek?mpfung des MaiszünslersOstrinia nubilalis Hübner geprüft. Die Parasiten wurden entweder auf Eiern der GetreidemotteSitotroga cerealella (Oliv.) oder auf Eiern der MehlmotteEphestia kuehniella Zell. gezüchtet. Die Freilassung erfolgte in den Versuchsparzellen durch Anbringen von Eikarten mit jeweils etwa 1000 parasitierten Wirtseiern an Bl?ttern von Maispflanzen in Abst?nden von 14 Metern. VierTrichogramma-Freilassungen in w?chentlichen Abst?nden mit jeweils 45000 Parasiten pro Hektar ergaben hohe Parasitierungsraten bei denO. nubilalis-Eiern und starke Verminderungen des Larvenbefalls. In den Parzellen, in denen aufS. cerealella-Eiern gezüchtete Parasiten freigelassen wurden, lagen die Parasitierungsraten zwischen 81,7 und 82,3% im Vergleich zu 63,0 und 84,3% bei den aufE. kuehniella gezüchteten Trichogrammen. Die Verminderung des bei der Ernte festgestelltenO. nubilalis-Larvenbefalls im Vergleich zur unbehandelten Kontrolle lag bei den aufS. cerealella gezüchteten Parasiten zwischen 75,5 und 94,8% verglichen mit 77,6 und 89,9% bei den aufE. kuehniella gezüchteten Tieren. Es gab somit keine signifikanten Unterschiede zwischen den beiden getestetenTrichogramma-St?mmen.

---

Summary The effectiveness of a strain ofTrichogramma evanescens Westw. especially adapted to the European corn borerOstrinia nubilalis Hübner was examined in 4 field experiments. The parasites were reared on either the Angoumois grain mothSitotroga cerealella (Oliv.) or the Mediterranean flour mothEphestia kuehniella Zell. and were released in separate experimental plots by attaching egg cards, each containing about 1000 parasitized host eggs, to corn leaves at distances of 14 meters in the field. FourTrichogramma treatments at 1 week intervals using 45000 parasites per hectar per treatment resulted in high parasitization rates ofO. nubilalis-eggs and large reductions in larval damage. In experimental plots whereT. evanescens, reared onS. cerealella-eggs, were released, the parasitization rates ofO. nubilalis-eggs varied between 81,7 and 82,3%, compared with 63,0 and 84,3% forT. evanescens reared onE. kuehniella. The reduction inO. nubilalis larval infestation at the harvest in the treated plots, compared to untreated controls varied between 75,5 and 94,8% forT. evanescens that was reared onS. cerealella, compared with 77,6 and 89,8% forT. evanescens that was reared onE. kuehniella. There were no significant differences in efficiency between the two tested methods of rearingTrichogramma.

     

Comparative study of freezing time and temperature for effective Plodia interpunctella control using typical storage containers

Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is a moth species that is able to feed on various vegetable commodities. Its control is economically critical for commercial food storing facilities such as warehouses. P. interpunctella causes quantitative and qualitative damage by eating important stored food crops such as dried Welsh onions (Allium fistulosum L.), and freezing treatment is a common method of control. To examine the effectiveness of freezing treatment, we changed the length of time of the conventional freezing method. The conventional method involves treatment below ?15 °C for 48 h, but we predicted that it would be effective with only 24 h freezing at ?25 °C. To test our theory, we conducted an experiment using three different frozen storage containers and assessed if the modified method was effective on the eggs and fourth instar larvae of P. interpunctella. Despite the temporary malfunctioning of one of the containers used in the experiment after incubation at 28 °C and 70% relative humidity for 10 days, the larval mortality rate was 100% and egg hatching rate was 0% in all samples, regardless of the treatment time. Further research is needed as this method is expected to decrease production costs and energy consumption and has the potential to be applied to other crops and pests.     

Spatial distribution of eggs by ovipositing Indian meal moths,Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

A series of increasing egg densities was obtained by releasing various numbers of female Plodia interpunctella (Hübner ) in rooms where dishes of moth rearing medium were evenly spaced on the floor. The number of larvae produced in each dish was taken as an indication of the number of eggs that had been laid. At all egg densities, the eggs were aggregated, and most of the distributions conformed quite well with the negative binormial, but the degree of aggregation denreased as mean egg density increased. The implications of the results for the development of ware-house sampling strategies are discussed.     

First Occurrence of <Emphasis Type="Italic">Trichogramma bruni</Emphasis> Nagaraja (Hymenoptera: Trichogrammatidae) Parasitizing Eggs of <Emphasis Type="Italic">Anticarsia gemmatalis</Emphasis> Hübner (Lepidoptera: Erebidae) in Brazil

The occurrence of Trichogramma bruni Nagaraja (Hymenoptera: Trichogrammatidae) is described for the first time parasitizing eggs of the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae) in Lapa, Paraná, Brazil. This parasitoid was successfully kept in the laboratory on eggs of the velvetbean caterpillar; previously, this species was mainly associated with forest and fruit trees environments, although snap beans and other annual crops were also recorded as hosting lepidopteran eggs parasitized by T. bruni. This is the sixth Trichogramma species recorded parasitizing eggs of A. gemmatalis on soybeans in Brazil.     

Characterization of polymorphic microsatellite markers in the Indian meal moth,Plodia interpunctella (Hübner)

The Indian meal moth, Plodia interpunctella (Hübner), is a serious and widespread pest of stored food commodities worldwide. Studies on the population genetics and breeding structure of P. interpunctella are lacking. Understanding the breeding structure of this pest has implications for its management. Fifteen microsatellite loci were isolated, cloned and characterized using an enrichment method. Forty individuals from six subpopulations were tested for polymorphism. Nine loci were found to be polymorphic. The number of alleles varied from three to six per locus.     

Application of the Laurell immunoelectrophoresis technique to the study of serological relationships between granulosis viruses

The Laurell technique of two-dimensional immunoelectrophoresis was used to distinguish between isolates of granulosis virus (GV) from Plodia interpunctella (GV strains A and B), Ephestia cautella, Spodoptera littoralis (GV strain 65), Pieris brassicae, and Cydia pomonella. Granules, alkali-soluble proteins, and virus particles of P. interpunctella GV strain A and granules of P. interpunctella GV strain B were used as sources of antigens. They were reacted with the immunoglobulins of antisera prepared against whole granules of each strain of virus. Peaks of precipitation were most clearly defined when antigens were pretreated with 0.1 m Na₂CO₃, 2% Triton X, and succinic anhydride, Granules and alkali-soluble proteins of P. interpunctella GV strain A treated in this way exhibited at least one peak of precipitation when reacted with each of the antisera studied. Four peaks were observed in both the homologous reaction and in the heterologous reaction with antiserum prepared against granules of P. interpunctella GV strain B. Four different peaks were present in the homologous reaction between immunoglobulins and virus particles of P. interpunctella GV strain A. Two peaks were present in the heterologous reaction with antiserum prepared against granules of P. interpunctella GV strain B and one in that with the antiserum prepared against granules of S. littoralis GV strain 65.     

Comparison of Yolk Production in Seven Pyralid Moth Species

Summary

The yolk proteins of six pyralid moths were analyzed and compared with the yolk proteins of Plodia interpunctella (Hübner). When cross-reacted in an Ouchterlony double immunodiffusion with antiserum raised to either total yolk proteins or purified vitellin from P. tnterpunctella, the yolk proteins of Anagasta kuehniella (Zeller), Cadra cautella (Walker), C. figulilella (Gregson), and Ephestia elutella (Hübner), closely related members of the subfamily Phycitinae, showed strong precipitation lines that consisted of four major yolk polypeptides (YPs). The yolk proteins from Amyelois transitella (Walker) were only weakly reactive, whereas yolk proteins from Galleria mel-lonella (L.) were not precipitated by either antiserum. Abdominal body walls (containing primarily fat body) from late pharate adult females were incubated in vitro and they secreted two major polypeptides that had molecular masses similar to the vitellogenins (YP1 and YP3) from P. interpunctella. In addition, ovarioles from late pharate adult females were incubated in vitro, and they secreted two major polypeptides that had molecular masses similar to YP2 and YP4 from P. interpunctella. When late pharate adult females were injected with ³⁵S-Met, the hemolymph of all species contained vitellogins that were secreted by their respective body walls in vitro. Ovarioles from injected females contained many labeled polypeptides, but there were four major bands that corresponded consistently to the vitellogenins secreted from the fat body and the two major polypeptides secreted from the ovarioles. These data show that the production of the major YPs in these closely related pyralid species is very similar, and that there is considerable conservation of immunological characters of yolk proteins in the subfamily Phycitinae.     

Does mass rearing of field collected Trichogramma brassicae wasps influence acceptance of European corn borer eggs?

The purpose of our study was to identify a trait that changes quickly during Trichogramma mass rearing, and that could therefore be used to monitor stock deterioration. Quality deterioration in mass reared Trichogramma wasps was evaluated by examining host acceptance behaviour of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) on the target host Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). We compared three replicate lines (designated ‘E’) reared in the laboratory on the factitious host Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) for 27 generations, a line ‘O’ reared in the laboratory on O. nubilalis for 24 generations, and a line ‘F’ reared in the laboratory on O. nubilalis for only two generations. All lines were initiated from field collections of O. nubilalis egg masses. We also evaluated natal host effects by rearing each line on E. kuehniella as well as on O. nubilalis for the last generation prior to testing. The percentage of wasps accepting the O. nubilalis egg mass was significantly higher for the E lines (69.6%) than for the F line (46.5%), while wasps of the O line showed intermediate (57.4%) acceptance. Thus, wasps laboratory reared on E. kuehniella performed better than wasps which had recently been collected in the field. Wasps of the O line showed extended probing behaviour compared to the other lines. Lines did not differ in the duration from the first host contact to the beginning of the drilling, probing or trembling behaviour. Natal host (E. kuehniella or O. nubilalis) did not affect acceptance of the target host O. nubilalis. Even though there is some evidence of adaptation to laboratory rearing conditions, we found no indication for quality deterioration in terms of acceptance behaviour of the target host O. nubilalis when T. brassicae was mass reared on the factitious host E. kuehniella.     

Gustatory perception of phytoecdysteroids in Plodia interpunctella larvae

Phytoecdysteroids are steroidal compounds produced by various plants that disrupt growth and development of insects eating them. They exhibit an insecticidal activity on a number of insect pests such as Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). In this study, we further evaluated whether phytoecdysteroids deter larvae of this species from feeding, by using four phytoecdysteroid molecules, commonly occurring in plants: 20‐hydroxyecdysone (20E), ponasterone A (PonA), polypodine B (PolB), and makisterone A (MakA). Fourth instar P. interpunctella avoided contact with food pellets treated with these phytoecdysteroids in a dose‐dependent way (2–30 mm ). In order to test whether this avoidance was mediated by taste sensitivity, we recorded the responses of taste neurons located in the lateral and medial sensilla styloconica of the galea. At least one neuron responded to each of these compounds in both sensilla. The neuron located in the medial sensillum had a detection threshold of 10^?6 m for PonA, 10^?4 m for 20E and PolB, and 10^?3 m for MakA. The lateral sensillum neuron responded with less intensity and its detection threshold was 10 times higher than that of the medial sensillum neuron. These results indicate that phytoecdysteroids are detected as deterrent stimuli by P. interpunctella larvae and that small structural differences significantly affect their biological activity.     

The scale response ofTrichogramma [Hymenoptera: Trichogrammatidae]: Variation among species in host specificity and the effect of conditioning

Host specificity and the effect of conditioning on a behavioral response to lepidopteran scales varied among the females of 4Trichogramma spp. observed in laboratory experiments.Trichogramma species nrPretiosum Riley andT. exiguum Pinto & Platner responded weakly toOstrinia nubilalis (Hübner) scales relative toHeliothis zea (Boddie) andManduca sexta (L.).T. maltbyi Nagaraja & Nagarkatti andT. minutum Riley did not discriminate between scales from these 3 hosts. Conditioning with various combinations of host scales and eggs did not alter host specificity, but in some cases, changed general responsiveness to scales. These were attributed to habituation, loss of appetitive drive due to long oviposition bouts, and associative learning. In general, the scale response seems to be innate and fairly nonspecific.      

IndigenousTrichogramma (Hym.: Trichogrammatidae) parasitizing eggs ofRhopobota naevana (Lep.: Tortricidae) on cranberries in British Columbia

Two indigenous species ofTrichogramma were reared from natural populations of the blackheaded fireworm,Rhopobota naevana (Hübner) infesting cranberries in British Columbia, Canada. One was identified asTrichogramma sp. nr.sibericum Sorokina and the other wasTrichogramma minutum Riley. Percentage of parasitized hosts increased during the season in an abandoned field, but decreased in a commercial field where pesticides were used. The potential ofTrichogramma as a biological control agent against the fireworm is discussed.     

Spatio‐temporal variation in Helicoverpa egg parasitism by Trichogramma in a tropical Bt‐transgenic cotton landscape

• 1 Understanding the spatio‐temporal dynamics of insects in agroecosystems is crucial when developing effective management strategies that emphasize the biological control of pests.
• 2 Wild populations of Trichogramma Westwood egg parasitoids are utilized for the biological suppression of the potentially resistant pest species Helicoverpa armigera (Hübner) in Bt‐transgenic cotton Gossypium hirsutum L. crops in the Ord River Irrigation Area (ORIA), Western Australia, Australia.
• 3 Extensive, spatially‐stratified sampling during a season of relatively high Trichogramma abundance found that spatial patterns of pest egg parasitism in the ORIA tend toward heterogeneity, and do not necessarily coincide with host spatio‐temporal dynamics. Both patterns of host egg density and mean rates of parasitism are not good indicators of parasitoid spatio‐temporal dynamics in ORIA cotton crops.
• 4 Parasitism rates can be significantly higher within the middle strata of the cotton plant canopy before complete canopy closure, despite a similar number of host eggs being available elsewhere in the plant.
• 5 Spatial variation in egg parasitism by Trichogramma in Bt‐transgenic cotton is evident at the between‐field, within‐field and within‐plant scale, and is not solely driven by host spatial dynamics. These factors should be considered when estimating Trichogramma impact on pest species during biological control and spatio‐temporal studies of host‐parasitoid interactions in general.

     

Large‐scale mating disruption of Ephestia spp. and Plodia interpunctella in Czech Republic,Greece and Italy

Field trials were carried out to evaluate the use of the pheromone (9Z,12E)‐tetradecadienyl acetate (TDA/ZETA) for mating disruption (MD) of Pyralidae moths associated with stored products, in most cases the Raisin moth, Ephestia cautella (Walker), Mediterranean flour moth, Ephestia kuehniella Zeller and Indianmeal moth, Plodia interpunctella (Hübner). The experiments were conducted in the Czech Republic, Greece and Italy during 2007 and 2008 in storage facilities that varied in their size and type, and included flour mills, retail stores, storage rooms with currants and raw grain stores. After a summer pre‐treatment monitoring period to assess moth population in, dispensers containing TDA were placed in the fall. Adjacent facilities without dispensers were used as control units. Pheromone‐baited traps were used to monitor the population fluctuation of the pyralid moths during the entire experimental periods. The presence of MD dispensers notably reduced the number of adults found in the traps in comparison with control rooms. Monitoring of female oviposition, measured as number of hatched larvae in cups containing food, indicated that there was a reduction in the number of larvae in the areas with MD dispensers. The results of the present work indicate that the use of mating disruption is feasible against pyralid moths in storage facilities, and should be further evaluated as a component of an integrated pest management based control strategy.     

Host Preferences of Trichogramma pretiosum and the Influence of Prior Ovipositional Experience on the Parasitism of Plutella xylostella and Pseudoplusia includens Eggs

Trichogramma wasps are generalist egg parasitoids used in biological control efforts. In a multi host situation they may preferentially parasitize a non-target host species to the detriment of the control program. Plutella xylostella Linnaeus (Lepidoptera: Plutellidae) is a very serious pest of cabbage, but is only one in a number of species in the ‘cabbageworm’ complex. We investigated the host preferences of Trichogramma pretiosum Riley (Hymenoptera: Chalcidoidea) when offered the eggs of Plutella xylostella and the eggs of Pseudoplusia includens Hübner (Lepidoptera: Noctuidae), another species in the ‘cabbageworm’ complex. Trichogramma pretiosum reared on the eggs of the factitious host Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) parasitized both Plutella xylostella and Pseudoplusia includens eggs under laboratory conditions. For both choice and no-choice experiments, T. pretiosum parasitized significantly more P. xylostella eggs than P. includens eggs. Prior ovipositional experience with one or other of the two host species had no effect on the subsequent parasitism levels of the two host species. The preference for P. xylostella eggs was also not affected by this prior ovipositional experience.     

The role of predators and parasites in controlling populations ofEarias insulana,heliothis armigera andBemisia tabaci on cotton in the Syrian Arab Republic

Studies on the relationship between insect pests and their predators and parasites were conducted in the Syrian cotton agro-ecosystem from 1980 up to 1983.Earias insulana (Boisduval) was found to be the most damaging pest, whileHeliothis armigera (Hübner) was not an annual returning problem. Among the entomophagous insects found, coccinellids were most numerous during the months June and July and the hemipterous predators were more abundant during August and September. When predator numbers were reduced with insecticide applications, a significant increase in the bollworm populations occurred, resulting in significant reductions in seed cotton yields. Parasites were relatively not important for the control of lepidopterous pests on cotton. Egg and larva populations ofE. insulana andH. armigera were parasitized byTrichogramma spp. andHabrobracon brevicornis Wesmael respectively. Populations ofBemisia tabaci (Gennadius) were heavily parasitized byEretmocerus mundus Mercet.      

Recovery of two exotic parasites,Trichogramma brasiliensis [Hym.: Trichogrammatidae] andEucelatoria bryani [Dip.: Tachinidae] fromHeliothis armigera [Lep.: Noctuidae] in tomato fields

Heliothis armigera (Hübner) is a major pest of several crops especially tomato and pulses in India. Indigenous natural enemies likeCarcelia illota Curr.,Campoletis chlorideae Uchida,Trichogramma chilonis Ishii andHexamermis sp are unable to exert adequate control ofH. armigera in tomato. Field trials were conducted with 2 exotic parasites,Trichogramma brasiliensis (Ashmead) andEucelatoria bryani Sabrosky in tomato fields around Bangalore. Both the parasites were recovered fromH. armigera in tomato fields. Field parasitism inH. armigera byT. brasiliensis ranged from 34.6 to 51.3%. WithE. bryani, the parasitism ranged from 0.0 to 8.0%.     

Trichogramma egg parasitism ofHelicoverpa armigera on short-duration pigeonpea intercultured with sorghum

The levels of egg parasitism byTrichogramma spp. (Hymenoptera: Trichogrammatidae) on populations ofHelicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were recorded on sorghum (Sorghum bicolor L.) and on two flushes of flowers on short-duration pigeonpea (Cajanus cajan L.).H. armigera oviposition was concentrated on the early flowering stage of sorghum and the flowering and early podding stages of both flushes of pigeonpea. Parasitism on sorghum increased rapidly as egg density increased and reached a peak of 74.6%. Parasitism on pigeonpea was concentrated onH. armigera eggs laid on the first flush of pigeonpea flowers with a maximum of 69.2%. These high levels of parasitism on pigeonpea coincided with the period of parasite activity on sorghum. The levels of parasitism then declined rapidly and only very low levels were detected on a second flush of flowers. This rapid decline resulted in the overall egg mortality caused byTrichogramma on pigeonpea to be low, with a maximum of 7.8% caused by parasitism, compared to 34.4% on sorghum. The pattern of parasitism suggests that a transfer of parasites occurred from sorghum to pigeonpea. The rapid decline of parasitism on the pigeonpea indicates that parasite populations cannot be sustained on pigeonpea once the influx from sorghum stops. The results are discussed in terms of a possible method of encouraging the transfer of parasites from sorghum to short-duration pigeonpea by producing a more continuous cropping environment.     

The relationship between egg load and fecundity among Trichogramma parasitoids

1. The relationships between parasitoid egg load, size, and age (3–72 h) for Trichogramma minutum, T. platneri, and T. pretiosum, reared from two factitious hosts, Ephestia kuehniella and Sitotroga cerealella, were evaluated to test the hypothesis that 24‐h egg load can be used to estimate the fecundity of Trichogramma parasitoids. 2. Egg load increased in relation to female age over the first 3 days of adult life for all three Trichogramma species to a mean egg storage capacity of 46.7 eggs for T. minutum, 41.1 for T. pretiosum, and 35.7 for T. platneri. At 24 h of age, T. minutum had matured enough eggs to fill 67% of its storage capacity, in comparison with 74% for T. pretiosum and 91% for T. platneri. There was a positive relationship between egg load and parasitoid size for all ages of the three Trichogramma species reared from both hosts (with the exception of T. platneri at 3 h post emergence), accounting for 14–69% of the variance in egg load. 3. The potential fecundity, realised (3 day cumulative) fecundity, and oviposition rate (potential fecundity/longevity) of T. platneri were all related linearly to size‐dependent variation in 24‐h egg load, but only the realised fecundity of T. pretiosum, and none of the reproductive characteristics of T. minutum. It is suggested that 24‐h egg load may not be an accurate measure of egg storage capacity in parasitoids and should be used cautiously to represent fecundity. 4. The potential fecundity of seven Trichogramma species reared from E. kuehniella varied from 55 to 150, but neither potential fecundity nor oviposition rate was related significantly to egg load (represented by eggs laid during first 24 h). Selection to avoid egg depletion in the attack of gregarious hosts appears most likely to account for the variation in potential fecundity among Trichogramma species.     

Effect of four different nutrition regimes on the alpha-amylase gene expression in the Indian moth,Plodia interpunctella

Plodia interpunctella (Hübner 1813) (Lepidoptera: Pyralidae) is a cosmopolitan species known to infest a wide range of dried plant materials, including legumes and cereals. In this study, enzyme activity and expression of alpha-amylase gene in larval P. interpunctella grown on four different nutrition regimes was studied. The different nutrition regimes caused differential change in expression of alpha-amylase gene. Compared with the control (artificial diet), the walnut regime caused a 10.8% increase in expression of the alpha-amylase gene, whereas 79.3, 52.5, and 7.5% decreases were observed in the larvae grown on dates, raisins and oleaster respectively. The results also showed that glucose repression varied among larvae feeding on different food diets. The results revealed that expression of the alpha-amylase coding gene was significantly reduced in the larvae grown on date and raisin containing high amounts of glucose. A biochemical assay indicated overlapping of alpha-amylase activity and expression. Complexity in expression of amylase genes suggests the existence of a negative feedback mechanism in the insect larvae. Different parameters can affect gene expression and activation, which may explain the results presented here.