Life tables of Venturia canescens (Hymenoptera: Ichneumonidae) parasitizing the Mediterranean flour moth (Lepidoptera: Pyralidae)

Effects of temperature, adult feeding, and host instar on life table parameters of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) parasitizing larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were studied in the laboratory. Experimental adults lived under various regimes of temperature (15, 20, 25, and 30 degrees C), food supply (with or without access to honey), and host instar (second, third, fourth, and fifth). Temperature increase resulted in higher values of the intrinsic rate of natural increase (r(m)), the net reproductive rate (R(o)), the finite capacity of increase (lambda), and the gross reproductive rate (GRR), whereas it was followed by decrease of the mean generation time (G) and the doubling time (DT) values. Feeding on honey caused remarkable increase of r(m), R(o), and GRR, whereas r(m) and lambda reached their maximum when full-grown hosts (fifth instar) were parasitized. This is the first time life table parameters of V. canescens have been studied. The findings of the current study are discussed on the basis of improving V. canescens performance as a biological agent against moth pests of stored products.     

Parasitism of Tuta absoluta (Lepidoptera, Gelechiidae) by Pseudapanteles dignus (Hymenoptera, Braconidae) under laboratory conditions

Laboratory studies were conducted to measure selected life history traits and the functional response of the parasitoid Pseudapanteles dignus (Muesebeck), a major enemy of Tuta absoluta (Meyrick) in tomato crops in South America. Newly mated P. dignus females were individually exposed to 10 host larvae in mines for 24 h. We determined developmental time from egg to pupal formation and pupal stage duration, female adult life span, fecundity, reproductive period, daily parasitism rate, and sex ratio of offspring. For the functional response experiment, treatments consisted of six host densities: 3, 5, 7, 10, 15, 20, or 30 larvae. The number and proportion of parasitized hosts were calculated for each density. The shape of the functional response curve was analyzed by logistic regression. P. dignus females attacked hosts daily, exhibiting modest lifetime fecundity (approximately 32 parasitized hosts per female) and a female-biased offspring sex ratio. Female adult life span was 36 d. P. dignus showed a type I functional response within the range of host densities tested. We observed that females detect and parasitize the host within a wide range of densities, including low densities. The functional response curve reached an asymptote at a mean density of six hosts per day and seemed not to be egg-limited. Percent parasitism was approximately 30%. The ecological implications of the results in relation to the potential of P. dignus for the biological control of T. absoluta in tomato are discussed.     

白蜡吉丁肿腿蜂对栗山天牛低龄幼虫的寄生作用

栗山天牛Massicus raddei（Blessig）是我国东北危害栎树的重要害虫。在对其进行生物防治研究中,通过功能反应实验方法探讨了利用寄生蜂白蜡吉丁肿腿蜂Sclerodermus pupariae Yang et Yao对栗山天牛低龄幼虫的寄生作用。结果表明：白蜡吉丁肿腿蜂在取食寄主补充营养的过程中,对栗山天牛1～2龄小幼虫的致死作用随着寄主密度的增加而显著提高,功能反应符合Holling Ⅱ型方程,平均每日最大致死量为0.53头。寄生作用功能反应符合Holling Ⅰ型方程,寻找时间21 d内的寄主密度阈限为4头。当该肿腿蜂密度固定为1头时,对栗山天牛致死作用和寄生作用的寻找效率均随寄主密度的上升而降低。当寄主密度固定不变时,随着寄生蜂密度的增加寄主的死亡数量线性升高,被寄生的寄主数量也上升,但该肿腿蜂对栗山天牛低龄幼虫致死作用和寄生作用的寻找效应均显著下降,表明白蜡吉丁肿腿蜂是防治栗山天牛低龄幼虫的良好天敌。研究结果对于合理评价白蜡吉丁肿腿蜂在生产上的控害能力和制定寄生蜂的林间释放应用技术规程提供了依据。     

Life history and life table of the host-feeding parasitoid <Emphasis Type="Italic">Hemiptarsenus varicornis</Emphasis> (Hymenoptera: Eulophidae)

Hemiptarsenus varicornis (Girault), a destructive host-feeding wasp, is an important biocontrol agent/larval ectoparasitoid of agromyzid leafminers worldwide. In the present study, the life history and life table of H. varicornis reared with Liriomyza trifolii (Burgess) were studied at a constant 27 °C. The developmental durations of female and male eggs, larvae, prepupae, pupae and total immature wasps were 1.00 and 1.00, 2.57 and 2.62, 0.45 and 0.37, 3.88 and 3.52, and 7.90 and 7.52 days, respectively. This wasp showed three types of host-killing behavior: reproductive parasitization (parasitism), non-reproductive host feeding (host feeding), and host stinging without oviposition or feeding (host stinging), resulting in 133.9, 303.8, and 84.2, respectively, killed host larvae. We confirm that H. varicornis is a strong synovigenic parasitoid, with an ovigeny index of 0.003. The number of host-feeding events was strongly correlated with parasitism, host-stinging events, longevity and total host mortality. The intrinsic rate of increase, the finite rate of increase, the net reproductive rate, the gross reproduction rate, and the mean length of a generation of H. varicornis were 0.3011/day, 1.3624/day, 66.22 offspring/individual, 168.33 offspring/individual, and 13.56 days, respectively. These results could contribute to a better understanding of the biocontrol efficiency of this destructive host feeder.     

Phenoloxidase in larvae of Plodia interpunctella (Lepidoptera: Pyralidae): molecular cloning of the proenzyme cDNA and enzyme activity in larvae paralyzed and parasitized by Habrobracon hebetor (Hymenoptera: Braconidae)

Phenoloxidase (PO) is a major component of the insect immune system. The enzyme is involved in encapsulation and melanization processes as well as wound healing and cuticle sclerotization. PO is present as an inactive proenzyme, prophenoloxidase (PPO), which is activated via a protease cascade. In this study, we have cloned a full-length PPO1 cDNA and a partial PPO2 cDNA from the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) and documented changes in PO activity in larvae paralyzed and parasitized by the ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae). The cDNA for PPO1 is 2,748 bp and encodes a protein of 681 amino acids with a calculated molecular weight of 78,328 and pI of 6.41 containing a conserved proteolytic cleavage site found in other PPOs. P. interpunctella PPO1 ranges from 71-78% identical to other known lepidopteran PPO-1 sequences. Percent identity decreases as comparisons are made to PPO-1 of more divergent species in the orders Diptera (Aa-48; As-49; and Sb-60%) and Coleoptera (Tm-58; Hd-50%). Paralyzation of host larvae of P. interpunctella by the idiobiont H. hebetor results in an increase in phenoloxidase activity in host hemolymph, a process that may protect the host from microbial infection during self-provisioning by this wasp. Subsequent parasitization by H. hebetor larvae causes a decrease in hemolymph PO activity, which suggests that the larval parasitoid may be secreting an immunosuppressant into the host larva during feeding.     

松褐天牛肿腿蜂对寄主松褐天牛三龄幼虫的功能反应

为评估松褐天牛肿腿蜂Sclerodermus sp.（膜翅目： 肿腿蜂科）对其寄主松褐天牛Monochamus alternatus 3 龄幼虫的控制作用, 通过功能反应试验, 研究了松褐天牛肿腿蜂对松褐天牛3 龄幼虫补充营养时期的捕食功能反应和补充营养后的寄生功能反应以及肿腿蜂的密度效应。结果表明： 当松褐天牛肿腿蜂密度固定为1 头/缸时, 肿腿蜂因补充营养对松褐天牛3 龄幼虫的捕食功能反应符合Holling Ⅱ型方程, 1 头松褐天牛肿腿蜂雌蜂对松褐天牛3 龄幼虫的最大致死量为9.48 头, 平均为3.75 头; 寄生作用的功能反应符合Holling Ⅰ型方程, 可知肿腿蜂的寄主密度阈限为4 头就能满足补充营养和寄生的需要; 在捕食和寄生两个阶段其对松褐天牛幼虫的寻找效应随着寄主密度的增加呈线性减弱。当松褐天牛幼虫密度固定为30 头/缸时, 随着肿腿蜂的密度增加, 其补充营养阶段的捕食作用和之后的寄生作用均呈线性升高, 寻找效应则呈线性减弱; 由蜂虫比和致死总量的模型可得肿腿蜂与天牛幼虫比例为0.9805（近1∶1）时, 可使松褐天牛幼虫死亡总数最大。这些结果表明, 松褐天牛肿腿蜂是松褐天牛幼虫期的有效天敌。本研究为评价松褐天牛肿腿蜂对寄主的控制能力提供了基础数据和方法, 并为其在野外的释放量提供了依据。     

Ratio-dependent parasitism with Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) on egg rafts of Nezara viridula (Linnaeus) (Hemiptera: Pentatomidae): effect of experimental variables and compatibility of 'ratio' and 'Holling' models

Abstract Egg rafts of Nezara viridula were exposed to the parasitoid wasp Trissolcus basalis in experimental arenas to establish the relationship of the rates of attack and parasitism to various combinations of arena size, parasitoid density, host density and parasitoid-to-host ratio. Arena sizes were varied in the ratio 1:9:63, with the largest having a search area of 1.44 m². Parasitoid and host densities were varied over a 27-fold range. The parasitoid-to-host ratios used were 1:1, 3:1 and 6:1. Finding time was related to a constant factor (flight propensity), rather than to the difficulty of finding (density of hosts). Initial attack rates were therefore related only to parasitoid numbers (or density), even at the lower densities and ratios. Parasitism rates (a function of attack rate per host) were thus also strongly related to parasitoid to host ratio, regardless of densities used and arena sizes. Even reducing host density, while keeping time and parasitoid density constant, increased the parasitism rate. A ratio model for parasitism rate was therefore compatible with the data but the more explicit Holling 'disc' equation was also compatible because handling time was sufficiently large to make it sensitive to the ratio of parasitoids to hosts for the densities used. We conclude that the two models would predict different results if the density of host egg rafts was in a range below one per square metre.     

Life tables and development of Bemisia argentifolii (Homoptera: Aleyrodidae) at different temperatures

The life history of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) on tomato (Lycopersicum spp.) was studied based on the age-stage, two-sex life table at 15, 20, 25, 28, 30, and 35 degrees C. The intrinsic rate of increase (r) at these temperatures is -0.0176, 0.0667, 0.1469, 0.1611, 0.1745, and 0.0989 d(-1), respectively. The relationship among the gross reproductive rate (GRR), the net reproductive rate (R0), and the preadult survivorship (l(a)) is consistent with GRR > l(a) x GRR > R0 for all results at different temperatures. The mean generation time is 81.9, 48.6, 28.4, 25.3, 22.1, and 18.2 d, respectively. The developmental rate of the egg stage at different temperatures fit a linear equation with a thermal summation 89.2 degree-days and a developmental threshold of 11.4 degrees C. The developmental rates of the nymphal stage fit the model of Stinner et al. and the parameters of C, Rmax, k1 and k2 were 0.085, 0.0833, 5.298, and -0.263, respectively.     

Biological parameters of Scirtothrips dorsalis (Thysanoptera: Thripidae) on selected hosts

Since its establishment in Florida in 2005, Scirtothrips dorsalis Hood, a highly polyphagous species, has become an economically important pest of ornamental plants and a potentially significant pest of vegetable and fruit crops. Fruit and vegetable production in Florida is trending toward significant adoption of organic methods and use of widely dispersed small fields in rapidly urbanizing landscapes. Landscape plants may serve as refugia from which S. dorsalis recruits can disperse to nearby fruit and vegetable plantings. Therefore, information on this pest's biology including how it is affected by various host species is needed to develop effective integrated pest management (IPM) programs. In the greenhouse and laboratory condition, we studied the effects of various host plants, development, diel flight activity, oviposition, and demographics of S. dorsalis. The pest preferred Jalape?o pepper and Knockout rose over the other hosts, and it was most active between 1000 and 1600 hours EST. Irrespective of the host species, the duration of each of the immature stadia varied within a narrow range, and their respective sizes were quite similar. Demographic parameters quantified included gross reproduction rate (GRR), net reproductive rate (R(o)), intrinsic rate of increase per day (R(m)), finite rate of increase per day (λ), and mean generation time (T). The pest population may increase by a factor of ≈ 1.09/d, so that it may double in 8 or 9 d. The above information should be helpful in the development of sound programs to manage S. dorsalis on various crops and in the formulation of detection strategies by quarantine officers.     

Ability to host regulate determines host choice and reproductive success in the gregarious ectoparasitoid Eulophus pennicornis (Hymenoptera: Eulophidae)

Abstract.  The age of Lacanobia oleracea (L.) in the final (sixth) larval stadium influences host choice and developmental success significantly in the gregarious ectoparasitoid Eulophus pennicornis (Nees). In choice tests, parasitoids with prior oviposition experience parasitize hosts in the second day of the sixth stadium most frequently. Parasitoid brood survival on normally-reared (i.e. fed) hosts declines monotonically with age such that mean progeny survival (egg–adult) is less than 20% for wasps developing on hosts parasitized on day 5 of the sixth stadium, as opposed to almost 50% when developing on those parasitized on day 1. Neck ligation of hosts increases the survival of wasp larvae developing on older hosts (days 4 and 5), whereas starved hosts produce progeny in similar numbers to fed hosts on most days during the final larval stadium. Hosts parasitized early in the stadium (days 1–3), although continuing to grow, do not exhibit the characteristic physical changes that non-parasitized larvae exhibit prior to pupation. However, hosts parasitized on days 4 and 5 form prepupae in appreciable numbers, particularly on day 5 where, regardless of treatment, over 80% of hosts attain this stage. Envenomated hosts behave similarly, an observation that suggests that it is the wasp's inability to arrest completely development in older hosts that is the significant factor in reducing the developmental success of the wasp. The findings are discussed in the light of the known endocrinological events in the host, and in relation to previously reported host manipulations induced by this wasp.     

黑色软蚧蚜小蜂生物学特性研究

黑色软蚧蚜小蜂Coccophagus yoshidae Nakayama在四川雅安地区一年发生6～7代,以低龄幼虫和蛹在网纹绵蚧2、3龄雌若虫和雌成虫体内越冬。该蜂的发育起点温度和有效积温分别为8.40℃和456.09日度。18℃、21℃、24℃、27℃和30℃恒温条件下的平均世代历期分别为44.60天、38.27天、30.83天、23.73天和20.73天。成虫需取食网纹绵蚧体液作补充营养。生殖方式为产雌孤雌生殖。成蜂羽化高峰在羽化后的第3～6天,每日的羽化高峰出现在8：00～12：00时。成蜂寿命及平均每蜂子代出蜂数量与补充营养和温度关系密切。该蜂对寄主有一定的选择性,偏好寄生较大的雌成虫,其次是2、3龄雌若虫。     

Host hemolymph proteins and protein digestion in larval Habrobracon hebetor (Hymenoptera: braconidae)

Host plasma proteins and protein digestion in larval parasitoids were studied during trophic interactions of the ectoparasitoid Habrobracon hebetor Say (Hymenoptera: Braconidae), with a host, larvae of the Indianmeal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). We could detect no apparent differences in host hemolymph protein patterns up to 72 h after paralysation and/or parasitization by H. hebetor. A 190 kDa putative apolipophorin I present in host hemolymph could not be detected in the midguts of feeding H. hebetor larvae indicating that it is rapidly digested. The major 60 kDa storage proteins (putative hexamerins) in host hemolymph were detected in the parasitoid midgut and were completely digested 24 h after cessation of feeding and the beginning of cocoon formation. Host hemolymph had a pH of about 6.4. The pH optima of the midgut proteinases in the larval parasitoid were in the alkaline region, but midgut fluid in feeding parasitoid larvae was about pH 6. 8. Based on enzyme activity against selected artificial proteinase substrates including azocasein, N-alpha-benzoyl-L-Arg p-nitroanilide (BApNA), succinyl-Ala-Ala-Pro-Phe p-nitroanilide (SAAPFpNA), succinyl-Ala-Ala-Pro-Leu p-nitroanilide (SAAPLpNA), and inhibition by selected proteinase inhibitors, serine proteinases appear to be the predominant class of enzymes involved in protein digestion in the midguts of H. hebetor. There is also an active aminopeptidase (LpNA) associated with the microsomal fraction of midgut preparations. There was no evidence for preoral digestion or ingestion of proteinases from host hemolymph by the parasitoid larva. There was a very active BApNAase in the soluble fraction of midgut extracts. This activity increased on a per midgut basis up to 24 h after the beginning of cocoon formation but decreased rapidly by 48 h. Two major (P1 and P3) and several minor proteinases were detected in midgut extracts of H. hebetor analysed with gelatin zymograms. The apparent molecular mass of P1 varied from 95 to 49 kDa depending on protein loading. P3 had an apparent molecular mass of 39 kDa that was independent of protein loading. In summary, electrophoretic evidence indicates that host hemolymph protein patterns do not change significantly for at least 72 h after paralysation by H. hebetor. The role, if any, of envenomization in preventing breakdown of hemolymph proteins during this time remains to be determined. Because the predominant host hemolymph proteins, a putative apolipophorin I and the putative hexamerins, are readily digested by the serine proteinases present in the midguts of this parasitoid larva, these or similar proteins would provide an easily digested source of dietary amino acids that could be used for development of artificial diets for this beneficial insect.     

Predation and life table of Feltiella acarisuga (Diptera: Cecidomyiidae) preying on eggs of Tetranychus urticae (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7 degrees C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower ( approximately 1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. The intrinsic rate of natural population increase (r), net reproductive rates (R(o)), gross reproductive rate (Sigmam(x)), generation time (T), doubling time (DT), and the finite rate of increase (lambda) of F. acarisuga were estimated by life table analysis at 0.1155/d, 15.25 eggs per female, 21.69 eggs per female, 23.6 d, 6.0 d, and 1.1225/d, respectively. Because the r value of F. acarisuga is relatively lower than that of T. urticae, frequent release of F. acarisuga may be necessary to suppress populations of T. urticae.     

Inhibition of juvenile hormone esterase activity in Lymantria dispar (Lepidoptera, Lymantriidae) larvae parasitized by Glyptapanteles liparidis (Hymenoptera, Braconidae)

Glyptapanteles liparidis is a gregarious, polydnavirus (PDV)-carrying braconid wasp that parasitizes larval stages of Lymantria dispar. In previous studies we showed that parasitized hosts dramatically increase juvenile hormone (JH) titers, whereas JH degradation is significantly inhibited in the hemolymph. Here we (i) quantified the effects of parasitism on JH esterase (JHE) activity in hemolymph and fat body of penultimate and final instars of L. dispar hosts and (ii) assessed the relative contribution of individual and combined wasp factors (PDV/venom, teratocytes, and wasp larvae) to the inhibition of host JHE activity. The effects of PDV/venom was investigated through the use of gamma-irradiated wasps, which lay non-viable eggs (leading to pseudoparasitization), while the effects of teratocytes and wasp larvae were examined by injection or insertion of these two components in either control or pseudoparasitized L. dispar larvae. Parasitism strongly suppressed host JHE activity in both hemolymph and fat body irrespective of whether the host was parasitized early (premolt-third instar) or late (mid-fourth instar). Down-regulation of JHE activity is primarily due to the injection of PDV/venom at the time of oviposition, with only very small additive effects of teratocytes and wasp larvae under certain experimental conditions. We compare the results with those reported earlier for L. dispar larvae parasitized by G. liparidis and discuss the possible role of JH alterations in host development disruption.     

Superparasitism and mutual interference in the egg parasitoid Anagrus delicatus (Hymenoptera: Mymaridae)

Abstract.

• 1 In nature, interference among Anagrus delicatus (Hymenoptera: Mymaridae) parasitoids reduced the per-capita number of hosts parasitized. Interference increased with parasitoid density.
• 2 Anagrus delicatus did not avoid parasitizing hosts that had recently been parasitized by conspecific wasps. Evidence indicated that this superparasitism was largely a random process, increasing with the ratio of parasitized to unparasitized hosts.
• 3 Individual parasitoid efficiency, the number of hosts killed per wasp per unit time, decreased with increasing wasp density. This occurred whether wasps searched the patch together (simultaneously) or one by one (sequentially), and was the result of an increase in time spent superparasitizing hosts at higher wasp density. This is known as indirect mutual interference.
• 4 Increasing numbers of parasitoids together on the same patch caused a significant decline in the rate and per-capita number of hosts parasitized. However, there was not a correspondent decline in searching efficiency with increasing wasp density (i.e. no direct mutual interference).
• 5 These forms of parasitoid density dependence should contribute to the stability of the host—parasitoid interaction.

     

Nutritional ecology of the interaction between larvae of the gregarious ectoparasitoid, Muscidifurax raptorellus (Hymenoptera: Pteromalidae), and their pupal host, Musca domestica (Diptera: Muscidae)

In this study we examined the relationship between clutch size and parasitoid development of Muscidifurax raptorellus (Hymenoptera: Pteromalidae), a gregarious idiobiont attacking pupae of the housefly, Musca domestica (Diptera: Muscidae). Host quality was controlled in the experiments by presenting female parasitoids with hosts of similar size and age. This is the first study to monitor the development of a gregarious idiobiont parasitoid throughout the course of parasitism. Most female wasps laid clutches of one to four eggs per host, although some hosts contained eight or more parasitoid larvae. In both sexes, parasitoids completed development more rapidly, but emerging adult wasp size decreased as parasitoid load increased. Furthermore, the size variability of eclosing parasitoid siblings of the same sex increased with clutch size. Irrespective of clutch size, parasitoids began feeding and growing rapidly soon after eclosion from the egg and this continued until pupation. However, parasitoids in hosts containing five or more parasitoid larvae pupated one day earlier than hosts containing one to four larvae. The results are discussed in relation to adaptive patterns of host utilization by gregarious idiobiont and koinobiont parasitoids.     

Variations in the life-history parameters of Hemipyrellia ligurriens (Diptera: Calliphoridae) in response to larval competition for food

Abstract. 1. Larval rearing densities of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae) in standardized carrion were manipulated in order to investigate changes in life-history parameters in response to larval competition for food.
2. Competition was of the typical scramble type. Survivorship remained high at densities up to 32 larvae g liver^-1 but decreased rapidly as larval density increased further.
3. Emergent adults were undersized with reduced fecundity and longevity. Variations in adult body size apparently reduced the effects of competition on larval mortality.
4. Females of dry weight corresponding to only 10.4% of the potential maximum emerged at the highest rearing densities of 128 larvae g liver-1. However, these females had a nearly four-fold increase in reproductive investment (per unit weight) when compared to the largest individuals.
5. The duration of larval development declined when competition was intense (i.e. at high larval densities).
6. The short adult life of H.ligurriens, combined with the unpredictability of larval habitat availability, may reduce the value of long-range dispersal so that females 'do better' by maintaining reproductive investment despite a concomitant decline in dispersal ability.     

Influence of initial egg density and host size on the development of the gregarious parasitoid <Emphasis Type="Italic">Bracon hebetor</Emphasis> on three different host species

Bracon hebetor (Say) (Hymenoptera : Braconidae) is a gregarious parasitoid that attacks a variety of important lepidopterous pests of stored product and in the field. In this study the effect of host species, size and larval competition on parasitoid size, survival and development were investigated. In laboratory studies, wasp eggs at a range of densities, were placed on larvae of different weight of three Lepidoptera host species namely Adoxophyes orana (Fischer von Röslerstamm, Tortricidae), Plodia interpunctella (Hubner, Pyralidae) and, Lobesia botrana(Dennis & Schiffermueller, Tortricidae). On A. orana survival of immature parasitoids was very low at all densities and different host weights. On L. botrana survival progressively reduced as egg density increased at both host weights examined for this host. Survival on P. interpunctella was significantly affected by egg density but not by host weight. Initial egg density had a significant effect on the size of emerging adults from each rearing host. Smaller adult parasitoids emerged as egg density per larva increased. Larval host weight of P. interpunctella and A. orana had a significant effect on the size of emerging adult parasitoids mainly at the higher egg densities used in these experiments. The above results of host quality on fitness of parasitoid are discussed.     

多胚发育寄生蜂腰带长体茧蜂在寄主亚洲玉米螟幼虫体内的发育

多胚发育的幼虫内寄生蜂腰带长体茧蜂Macrocentrus cingulum的卵、胚胎和幼虫在寄主亚洲玉米螟Ostrinia furnacalis幼虫血腔内发育,通常1枚卵可以分裂增殖为数百只胚胎。本文通过定时解剖寄生的寄主幼虫,初步了解了腰带长体茧蜂多胚的形成过程及其在寄主体内的发育情况。结果表明：以4龄末期亚洲玉米螟幼虫为寄主时,寄生蜂卵产入寄主体内10 min左右开始卵裂,1天左右,初级胚胎从卵壳中被释放出来。之后胚胎在胚外膜内持续分裂产生大量二级胚胎形成桑葚胚。寄生后3天左右,二级胚胎从胚外膜中被释放出来,进入胚胎发育阶段。寄生后6天左右,胚胎进入胚带形成阶段。寄生后8天左右,胚带伸长,头尾形成。寄生后9天左右,身体分节完成,部分幼虫孵化,蜕去胚外膜。寄生后13天左右,蜂幼虫从寄主体内啮出。胚胎在发育初期体积变化不大,但从胚带形成开始,体积则迅速增大。腰带长体茧蜂与另一多胚发育寄生蜂佛州点缘跳小蜂Copidosoma floridanum在胚胎发育进程上明显不同,体现了它们对各自寄主的适应。     

Effect of host quality of Callosobruchus maculatus (Coleoptera: Bruchidae) on performance of the egg parasitoid Uscana lariophaga (Hymenoptera: Trichogrammatidae)

Development and reproductive success of the solitary egg parasitoid Uscana lariophaga Steffan were examined after development in eggs of the bruchid storage pest Callosobruchus maculatus Fabricius reared at either low or high densities on cowpea seeds and laid at day 1 and 4 of maternal life. Both bruchid larval competition and maternal age negatively affected egg size, but the latter more than the former. Uscana lariophaga reared in small hosts developed slower, were smaller and produced fewer eggs compared to parasitoids reared in large hosts. Fecundity of the parasitoid was heavily influenced by host egg size. This was reflected in the values for the intrinsic rate of increase of U. lariophaga, which differed for wasps that developed in host eggs laid by bruchid females of different age. Wasps allocated marginally more female offspring to larger hosts.