中国北部湾白骨壤红树林的虫害与研究对策

危害北部湾白骨壤的主要害虫是广州小斑螟 (Oligochroacantonella)幼虫、双纹白草螟 (Pseudcatharylladuplicella)幼虫和广翅蜡蝉 (Euricaniasp.)成虫。广州小斑螟喜食害白骨壤叶片 ,造成大量叶片的枯干和枝条的死亡 ,最高可导致林木 73 %的叶面积危害。室内培养发现广大腿小蜂 (Brachymeriasp .)、啮小蜂 (Tetrastichussp .)可寄生广州小斑螟的蛹 ,终止其羽化过程。虫害具有突发性、专一性、快速扩展的特点。海水淹没可明显抑制虫害。讨论了虫害的发源、爆发的原因、生态效应和防治途径 ,并指出深入研究的方向     

灭幼脲Ⅲ号、苏云金杆菌防治广州小斑螟药效试验

广州小斑螟Oligochroa cantonella(Caradja)是红树林的主要害虫,主要为害白骨壤Avicennia marina,在深圳市福田红树林保护区每年发生2～3代,其幼虫附着于叶片背面,取食下表皮和叶肉,留下薄薄的上表皮,给防治带来困难.     

东北玉米螟一代区微孢子虫、玉米螟和玉米之间相互关系初探

田间试验表明,玉米螟微孢子虫病垂直传播时发病较重,收获期虫口密度显著降低,水平传播时发病较轻,虽然发病率高达91.5—95.5％,虫口密度降低也不显著。越冬期染病螟虫虫口进一步降低,至前蛹期达到高峰,但残存虫仍有近半数带病虫羽化成为新的传染源。试验还表明,在单株含虫1—12头范围内,两个玉米品种单株每增1虫减产1.32—1.39％,另一品种不同虫量处理的产量无显著差异,表现高度耐螟,微孢子虫和耐螟品种在控制玉米螟虫口方面有协同作用。     

无瓣海桑和白骨壤植株根系时空分布特征

无瓣海桑和白骨壤是我国红树林造林中较具代表性的两种植物,通过对10龄无瓣海桑纯林、10龄白骨壤纯林、6龄无瓣海桑纯林和6龄白骨壤纯林的调查分析发现:1)无瓣海桑和白骨壤植株根系水平分布的半径和地下根系垂直深度均随树龄的增加而增加,其中10龄无瓣海桑和白骨壤植株的水平分布半径分别为30.6 m和3.85 m,6龄无瓣海桑和白骨壤植株的水平分布半径为9.47 m和2.23 m; 10龄和6龄无瓣海桑和白骨壤植株的地下根系分布深度分别为60 cm和40 cm; 2)无瓣海桑和白骨壤植株地表呼吸根系密度、高度、基径的分布范围会随其树龄的增加而增加,但其根系密度、高度和基径总体表现为由树冠向外逐渐减小; 3)无瓣海桑和白骨壤植株地下根系主要分别于0—20 cm表层,地下根系密度随树龄的增加而增多,具体如10龄无瓣海桑和白骨壤根系分布深度为60 cm,其中76.3%和77.6%根系分布于0—20 cm深度; 6龄无瓣海桑和白骨壤根系分布深度为40 cm,其中91.9%和91.6%根系集中于0—20 cm土层。这些结果能为进一步理解红树林的促淤保滩功能提供新启示。     

上海地区草坪害虫的发生为害初步调查

据作者初步调查 ,2种草坪害虫 :稻切叶野螟Psaralicarsisalis (Walker)和灰翅夜蛾Spodopteramauritia (Boisduval)在上海均以幼虫在土下越冬 ,1年发生 5代 ,后期存在世代重叠现象。灰翅夜蛾虫口密度一直到 7月份都较低 ,8月份虫口密度上升很快 ,所以在上海地区第 3 ,4代幼虫为害最严重 ;稻切叶野螟的幼虫发生期比灰翅夜蛾迟 1 0d左右 ,以 9～ 1 0月份虫口密度最高。在矮生百幕达草坪中稻切叶野螟虫口密度明显高于灰翅夜蛾 ;而在高羊茅、黑麦草等草坪中灰翅夜蛾的虫口密度则远远高于稻切叶野螟。     

不同红树植物群落中大型底栖动物群落的比较

2005—2006年对广东湛江红树林国家级自然保护区湿地三种红树植物群落(白骨壤 桐化树群落、桐花树群落、木榄 桐花树群落)的大型底栖动物群落特征进行了分析研究。白骨壤 桐化树群落大型底栖动物群落的物种数、栖息密度、生物量、丰富度指数和多样性指数均最高,优势度指数居中,均匀度指数略低于桐花树群落;桐花树群落大型底栖动物物种数急剧减少,尤其是底内型、底上附着型和穴居型种类减少明显,生物量和栖息密度下降到最低,由于个体数种间分配较为均匀而导致优势度指数下降而均匀度指数增高,虽丰富度指数略低于白骨壤 桐化树群落,但多样性指数接近于白骨壤 桐化群落;木榄 桐花树群落,大型底栖动物群落的物种数,尤其是穴居型和底内型种数继续减少,但生物量和栖息密度有所上升,个体数种间分配不均匀而使优势度指数增高而均匀度下降,加上丰富度指数最低,故多样性指数最小。白骨壤 桐化树群落优势种的生活型是底内型和穴居型;桐花树和木榄 桐花树群落优势种的生活型均是穴居型。三种红树植物群落中的大型底栖动物群落的GS/GSB分别为0.48、0.63、0.80。相同红树植物群落大型底栖动物群落结构都较为相似,木榄 桐花树群落的相似性最高,而不同红树植物群落大型底栖动物群落特征的差异明显,反映了不同红树群落对底栖动物群落作用的差别,同时也展示了各种大型底栖动物对不同红树群落生境的适应情况。     

两种红树植物白骨壤(Avicennia marina )和桐花树(Aegiceras corniculatum)的耐淹性

以两种红树植物白骨壤（Avicennia marina（Forsk.）Vierh.）和桐花树（Aegiceras corniculatum （L.） Blanco）幼苗为材料,在梯度海面高程的野外人工平台上开展了为期1a的淹水胁迫实验。3座平台作为重复,每座设置8个梯度,相邻梯度间高度相差10cm,幼苗立地基质平面的海面高程320~390cm。实验1a后测定1a幼苗的生长状况及与一些生理指标。结果表明：小高程生境对两种幼苗茎的纵向生长均有显著促进作用,但白骨壤幼苗茎生长高度是桐花树的7.5倍。与白骨壤相比,桐花树幼苗有较高的叶片保存率。白骨壤幼苗生物量在各器官分配为：茎〉根〉叶,3个器官平均所占比例分别为56.7%,25.7%和17.6%;桐花树则为：叶〉根〉茎,3个器官平均所占比例分别为49.6%,33.0%和17.4%。小高程生境对白骨壤幼苗全株生物量有较强的促进效果,桐花树幼苗则在中等高程生境中有较大生物量。在任一高程组,桐花树幼苗叶片叶绿素含量均大于白骨壤幼苗,但两种幼苗叶绿素a/b比值差异不显著。无论在叶片还是根系中,桐花树幼苗的活性氧清除酶类活性均高于白骨壤幼苗,表明在相同高程生境中桐花树幼苗比白骨壤幼苗面临更大的困难。综合实验结果和野外观察,可看出白骨壤耐淹水能力高于桐花树;仅从植物本身的生理特性考虑,可确定北部湾沿海白骨壤造林滩面高程不宜低于平均海面30cm,桐花树不应低于当地平均海面。     

湛江特呈岛红树植物群落结构特征

2008年6月,采用样方调查法对湛江特呈岛红树植物群落结构及白骨壤(Avicennia marina)的种群特征进行了全面调查.结果表明:该地区红树林是白骨壤纯林以及白骨壤为主,有红海榄(Rhizophora stylosa)、木榄(Bruguieragymnorrhiza)和桐花树(Aegiceras corniculatum)的混交林.白骨壤在潮滩上连续分布,红海榄、木榄和桐花树生长于近陆林缘及潮滩的中部,物种多样性指数由陆缘向海缘呈降低趋势.通过分析白骨壤种群的株高、地径在潮滩上的变化规律得出年幼的个体聚集于近陆林缘,近海林缘较少.白骨壤种群的年龄结构为增长型,但是根据生境条件及白骨壤种群在海滩上的分布格局,分析得出该红树林资源处于退化的状态.     

白骨壤次生木质部生态解剖学研究

测量了深圳红树林鸟类自然保护区8个不同白骨壤(Avicennia marina)种群采样点土壤的盐分、p H值和养分,应用生物显微技术和电镜技术观察了白骨壤次生木质部的结构形态,不同样地白骨壤次生木质部均具有:(1)纤维状导管;(2)螺旋雕纹和附物;(3)薄壁细胞含淀粉粒;(4)内含韧皮部。依据结构-功能解剖学的研究结果,这些特化结构均有利于提高白骨壤在"生理干旱"生境下栓塞修复能力,增进水分输导的安全性。对白骨壤次生木质部数量特征和土壤理化因子作逐步回归分析,结果表明:随土壤盐度和土壤有机质含量增大,在遭受"生理干旱"越来越严重的情况下,白骨壤能形成更高的复孔率,相邻两导管接触壁平均厚度增加,这可能是适应异质生境的结果。     

汞胁迫对白骨壤(Avicennia marina)幼苗生理生态的影响

为了解红树植物的重金属抗性机制,对白骨壤(Avicennia marina)幼苗进行不同浓度Hg2+(1、5、10、50、100 mg·L-1)的胁迫实验,测定并分析了Hg2+胁迫对白骨壤幼苗叶片的光合作用和抗氧化酶活性的影响.结果表明:叶片净光合速率随着胁迫时间的延长而降低,高浓度(≥150 mg·L-1)Hg2+胁迫下叶片的净光合速率低于中低浓度胁迫,且高浓度胁迫的叶片净光合速率在48 h后快速下降;叶片净光合速率与胞间二氧化碳浓度呈极显著负相关,叶绿素含量随Hg2+浓度的增加而降低.气孔导度在不同浓度胁迫下反应不同,低浓度Hg2+对白骨壤幼苗光合的影响可能是气孔因素,中高浓度Hg2+对白骨壤幼苗光合作用的抑制主要是非气孔因素.低浓度Hg2+胁迫,白骨壤幼苗叶片SOD、POD活性升高,表现了一定的抗逆性,而高浓度表现为抑制作用,基本在100 mg·L-1 Hg2+胁迫下活性达到最低值.说明Hg2+可以抑制白骨壤叶片的光合活性,高浓度Hg2+胁迫削弱了白骨壤的活性氧清除能力,植物极易受到伤害.     

Assessing within habitat variability in plant demography, faunal density, and secondary production in an eelgrass (Zostera marina L.) bed

This investigation addressed faunal relationships with habitat structure within a Zostera marina community targeting differences between seagrass bed edge and interior. Z. marina biomass was significantly higher from the interior portions of the bed compared to the edge, but shoot density did not vary. Additionally, leaf width and length were significantly greater in the interior of the bed, suggesting greater total leaf area. Densities of larger organisms (> 0.85 mm) were significantly greater in vegetated samples (Z. marina edge and interior) compared to unvegetated, but an analysis of similarities demonstrated significant faunal community differences among each of the identified habitats. Densities of small organisms (0.25-0.85 mm), however, were significantly greater at Z. marina edge compared to unvegetated samples and Z. marina interior. Additionally, secondary production (μg AFDW day^− 1) was estimated based on the size distribution of taxa and showed significantly greater production from samples gathered in Z. marina compared to unvegetated samples. The relative size distribution of taxa was assessed using regression analysis and results showed that the size distribution was similar for samples collected at edge and interior Z. marina, but these distributions differed significantly when compared to unvegetated samples. The results of this study suggest that although similarities exist between edge and interior portions of Z. marina beds, especially compared to unvegetated habitats, noteworthy differences in faunal density, species composition, size distribution, and secondary production exist between edge and interior Z. marina.     

An investigation of the mechanisms for sterol synthesis and dietary sterol bioconversion in the heterotrophic protists Oxyrrhis marina and Gyrodinium dominans

The ability of the marine heterotrophic protists Oxyrrhis marina and Gyrodinium dominans to synthesize sterols de novo and modify dietary sterols was investigated using ¹³C-labeled substrates. De novo sterol synthesis of O. marina was determined by incorporation of ¹³C acetate into the culture medium. For G. dominans which has low tolerance of acetate, a protozoan prey Perkinsus marinus that cannot synthesize sterols, was cultured with ¹³C acetate then fed to G. dominans. Both heterotrophs utilized dietary ¹³C to synthesize fatty acids de novo, but not sterols. The ability of O. marina and G. dominans to alkylate, saturate, and desaturate dietary sterols was tested using P. marinus incorporated with ¹³C-labeled cholesterol as prey. O. marina did not modify the dietary ¹³C-cholesterol, but G. dominans produced 5 labeled sterols (brassicasterol, C28:1, and unknown C28, C29 and C30 sterols) indicating that G. dominans has the ability to desaturate and alkylate dietary cholesterol. The ability of O. marina and G. dominans to dealkylate dietary sterols was tested by feeding them gelatin acacia microspheres (GAMs) containing ¹³C-labeled brassicasterol. Neither heterotroph dealkylated brassicasterol to make cholesterol, but G. dominans alkylated and saturated brassicasterol to make 2 sterols (C29:1 and C30:0). The lack of dealkylation of brassicasterol by both protist species suggests problems with the substrate and/or delivery system since previous studies suggest that dealkylation of brassicasterol occurs when either species is fed algae containing this sterol.     

Extension of the breeding season and its effects on fertilization and development in two species of lugworm (Arenicola marina and A. defodiens)

In the autumn/winter breeding polychaetes, Arenicola marina and A. defodiens, spawning can be advanced or delayed by a number of months through temperature manipulation of the adults. However, this manipulation may have significant consequences for fertilization rates and embryo developmental success and so in vitro fertilizations were performed to assess the impact of manipulation. Firstly, we used oocytes and sperm obtained from advanced or delayed individuals. For both species, using gametes from 4 weeks advanced individuals did not result in a significant reduction in development, however, gametes from individuals advanced (A. marina only) or delayed by 8 weeks resulted in significantly fewer embryos developing normally. Reciprocal crosses of temperature-manipulated A. marina gametes (from 4 weeks advanced and 4 weeks delayed individuals) with those at the natural spawning time confirmed that the reduction in developmental success in both was attributable to the oocytes. After 5 h post-fertilization, the majority of oocytes from advanced individuals had fertilized, but by 24 h most were abnormal. For fertilizations with gametes from delayed individuals, nearly 100% of the embryos were developing normally after 24 h, but after 144 h significantly more were abnormal in crosses involving oocytes from delayed females. Although both species have reproductive plasticity to extend their breeding season, the significant reduction in the numbers of competent larvae produced as the spawning is delayed or advanced further may be a significant bottleneck in aquaculture and it may also have considerable implications for the long-term reproductive success of a population in response to environmental change.Sympatric populations of the species exist in many locations and the inherent variability in the breeding seasons could allow spawning times to overlap. Artificially delaying A. marina individuals enabled fertilizations to be performed with A. defodiens at the natural spawning time in the laboratory. Both conspecific fertilizations produced 100% trochophore larvae after 120 h, but A. defodiens oocytes failed to fertilize after incubation with A. marina sperm, in comparison to the A. marina oocytes incubated with A. defodiens sperm where 40% developed to the trochophore stage. This asymmetric gamete incompatibility may be one of a suite of mechanisms to minimise hybridisation.     

Genetic characterization of Zostera asiatica on the Pacific Coast of North America

We gathered sequence information from the nuclear 5.8S rDNA gene and associated internal transcribed spacers, ITS-1 and ITS-2 (5.8S rDNA/ITS), and the chloroplast maturase K (matK) gene, from Zostera samples collected from subtidal habitats in Monterey and Santa Barbara (Isla Vista) bays, California, to test the hypothesis that these plants are conspecific with Z. asiatica Miki of Asia. Sequences from approximately 520 base pairs of the nuclear 5.8S rDNA/ITS obtained from the subtidal Monterey and Isla Vista Zostera samples were identical to homologous sequences obtained from Z. marina collected from intertidal habitats in Japan, Alaska, Oregon and California. Similarly, sequences from the matK gene from the subtidal Zostera samples were identical to matK sequences obtained from Z. marina collected from intertidal habitats in Japan, Alaska, Oregon and California, but differed from Z. asiatica sequences accessioned into GenBank. This suggests the subtidal plants are conspecific with Z. marina, not Z. asiatica. However, we found that herbarium samples accessioned into the Kyoto University Herbarium, determined to be Z. asiatica, yielded 5.8S rDNA/ITS sequences consistent with either Z. japonica, in two cases, or Z. marina, in one case. Similar results were observed for the chloroplast matK gene; we found haplotypes that were inconsistent with published matK sequences from Z. asiatica collected from Japan. These results underscore the need for closer examination of the relationship between Z. marina along the Pacific Coast of North America, and Z. asiatica of Asia, for the retention and verification of specimens examined in scientific studies, and for assessment of the usefulness of morphological characters in the determination of taxonomic relationships within Zosteraceae.     

Stage dependent habitat use under conflicting predation pressure: An experimental test with larval and juvenile two-spotted gobies, Gobiusculus flavescens Fabricius

The effect of size, predator types and presence of multiple predators on the microhabitat use of larvae and juveniles of a sublittoral, semipelagically schooling fish, the two-spotted goby (Gobiusculus flavescens), was tested in two experiments. Larvae (15 and 25 days old, Experiment I) and juveniles (mean ± 1 S.E.: small, 15.9 mm ± 1.28; medium, 19.2 mm ± 1.43; and large, 23.4 mm ± 1.67, Experiment II) were allowed to choose between two sections of the tanks; an upper, representing a water column habitat, and a lower, artificially vegetated, representing the hyperbenthic habitat. Position of larvae or juveniles and the activity level of juveniles were recorded. Predator treatments were: (I) no predators (control), (II) a pelagic predator, the jellyfish Aurelia aurita L., (III) a hyperbenthic predator, the mysid Praunus flexuosus O.F. Müller or (VI) both predator types simultaneously. In Experiment I predators were restricted to the habitat which they were chosen to represent, while goby larvae could move freely. In Experiment II both predators and juvenile gobies were allowed to move freely between compartments.Increasing age caused larval gobies, but not juveniles to shift downwards. Only 25-day-old larvae and small juveniles avoided the mysid by shifting upwards. Larval response to A. aurita was also size dependant: 25-day-old larvae avoided medusae by shifting downwards, while 15 day olds did not. Emergent multiple predator effects were found for the vertical distribution of 15-day-old larvae and small juveniles. Larger juveniles were more active than smaller, both in the upper and the lower sections of tanks. P. flexuosus caused juvenile gobies in their vicinity (i.e. in the lower section) to increase their activity level, while small juveniles (but not medium-sized or large) increased their activity level even when further away (i.e. in the upper section). The presence of A. aurita led to a reduction in activity of small juveniles in its vicinity (i.e. in the upper section), while no response was observed among older juveniles or juveniles further away from the predator (i.e. in the lower section). Emergent multiple predator effects on the activity level of juveniles were not observed.     

Experimental test of biodeposition and ammonium excretion from blue mussels (Mytilus edulis) on eelgrass (Zostera marina) performance

Blue mussels and eelgrass have been found to coexist in many locations. However, knowledge of the interactions between these species is limited. Two experiments were conducted in the laboratory, a “Deposit” and an “Epiphyte” experiment. The Deposit experiment examined possible effects of increasing load of blue mussel (Mytilus edulis) biodeposits on sediment biogeochemistry and eelgrass (Zostera marina) performance. Z. marina mesocosms received normal or high loads of mussel biodeposits (Normal and High), while no biodeposits were added to the Control. High dosage had overall negative effects on Z. marina, which was reflected as lower leaf numbers and biomass and accumulation of elemental sulphur in rhizomes. The sediment biogeochemical conditions were altered, as the mussel biodeposits enhanced sulphate reduction rates and increased sulphide concentrations in the porewater, which may result in sulphide invasion and reduced growth of Z. marina.In the Epiphyte experiment effects of mussel excretion, with particular emphasis on ammonium, on the growth of Z. marina and their epiphytes were examined. A thick cover of epiphytes developed on Z. marina growing together with M. edulis, and the relative growth rate was reduced with 20% compared to plants from control without mussels. Overall the experiments showed negative effects on Z. marina growing together with M. edulis, thereby supporting a preceding field study by Vinther et al. [Vinther, H.F., Laursen, J.S., Holmer, M. 2008. Negative effects of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds in Flensborg fjord, Denmark. Est. Coast Shelf. Sci. 77, 91-103.].     

Vertical Distribution of Plant-parasitic Nematodes in Sandy Soil under Soybean

Vertical distribution of five plant-parasitic nematodes was examined in two north Florida soybean fields in 1987 and 1988. Soil samples were collected from 0-15 cm, 15-30 cm, and 30-45 cm deep at each site. Soil at the three depths consisted of approximately 96% sand. More than 50% of Belonolaimus longicaudatus population densities occurred in the upper 15-cm soil layer at planting, but the species became more evenly distributed through the other depths as the season progressed. Criconemella sphaerocephala was evenly distributed among the three depths in one field but was low (< 20% of the total density) in the upper 15 cm at a second site. Maximum population densities of Pratylenchus brachyurus were observed at 15-30 cm on most sampling dates. Vertical distributions of Meloidogyne incognita and Paratrichodorus minor were erratic and showed seasonal variation. A diagnostic sample from the upper 0-15 cm of these soybean fields revealed only a minority of the populations of most of the phytoparasitic species present.     

夏蜡梅种群结构与分布格局研究

在夏蜡梅(Sinocalycanthus chinensis)主要分布地设置11个代表性样地,研究了种群结构与空间分布格局,并对种群密度与主要环境因子进行相关性分析。结果表明,大多数夏蜡梅种群幼年阶段的个体较丰富,种群自然更新良好;样地群落夏蜡梅以集群分布为主;在透光率低、林分郁闭的群落中夏蜡梅聚集强度高,但种群更新不良、幼苗缺乏。因此,夏蜡梅适合在相对开敞的遮阴环境下生长,过于郁闭林地应采取适度间伐上层乔木、疏除过密灌木的抚育保护措施。     

Microbial diversity of biofilm communities in microniches associated with the didemnid ascidian Lissoclinum patella

We assessed the microbial diversity and microenvironmental niche characteristics in the didemnid ascidian Lissoclinum patella using 16S rRNA gene sequencing, microsensor and imaging techniques. L. patella harbors three distinct microbial communities spatially separated by few millimeters of tunic tissue: (i) a biofilm on its upper surface exposed to high irradiance and O₂ levels, (ii) a cloacal cavity dominated by the prochlorophyte Prochloron spp. characterized by strong depletion of visible light and a dynamic chemical microenvironment ranging from hyperoxia in light to anoxia in darkness and (iii) a biofilm covering the underside of the animal, where light is depleted of visible wavelengths and enriched in near-infrared radiation (NIR). Variable chlorophyll fluorescence imaging demonstrated photosynthetic activity, and hyperspectral imaging revealed a diversity of photopigments in all microhabitats. Amplicon sequencing revealed the dominance of cyanobacteria in all three layers. Sequences representing the chlorophyll d containing cyanobacterium Acaryochloris marina and anoxygenic phototrophs were abundant on the underside of the ascidian in shallow waters but declined in deeper waters. This depth dependency was supported by a negative correlation between A. marina abundance and collection depth, explained by the increased attenuation of NIR as a function of water depth. The combination of microenvironmental analysis and fine-scale sampling techniques used in this investigation gives valuable first insights into the distribution, abundance and diversity of bacterial communities associated with tropical ascidians. In particular, we show that microenvironments and microbial diversity can vary significantly over scales of a few millimeters in such habitats; which is information easily lost by bulk sampling.     

Consumption and utilization of a soyflour-wheat germ diet by larvae of the tobacco budworm parasitized by the tachinidEucelatoria sp

The number ( \(\bar X\) =2.4) ofEucelatoria sp. maggots that completed development in 4th- or 5th-instar larvae of the tobacco budworm (TBW),Heliothis virescens (F.), was significantly greater (P<0.05) than the number ( \(\bar X\) =1.2) that completed development in 3rd-instar larvae. Maggot development time decreased with increasing number of maggots per host larva. It also decreased with advancing larval instars. The range was 6.9±1.1 days in early 3rd-instar TBW larvae and 5.0±0.8 days in early 5th-instar TBW larvae. Unparasitized 3rd- or 4th-instar TBW larvae consumed significantly more food than did similar aged larvae parasitized byEucelatoria sp., but larvae parasitized during the early 5th-instar consumed more food than did similar aged unparasitized larvae. Consumption by 4th- or 5th-instar larvae increased significantly as maggot densities increased from 1 to 3 per host larva, but decreased at a density of 4 or more maggots per host larva. Although body weight gain and consumption were both significantly reduced 48 and 120 h after parasitization of late 3rd-instar larvae (6 days old), the approximate digestibility (AD) value was significantly greater for parasitized than for unparasitized larvae. Unparasitized larvae were more efficient in converting digested food to body substance (ECD) than parasitized larvae, but the efficiency in conversion of ingested food to body substance (ECI) was similar for both parasitized and unparasitized larvae.