Dispersal and development of bagworm larvae (Lepidoptera: Psychidae) on three host plants

The present study investigated the development and dispersal of bagworm larvae, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), on three hosts: arborvitae, Thuja occidentalis, blue spruce, Picea pungens, and juniper, Juniperus virginiana. The biomass of larvae was recorded at repeated intervals at 21 field sites. The relative quality of plants varied during larval development: early in the season, larvae were heavier on juniper and arborvitae than on blue spruce; late in the season, in contrast, larvae and pupae were lighter on juniper than on the two other plants. Larvae on blue spruce pupated later than those on arborvitae. In the laboratory, feeding rate and larval growth were not influenced by the density of larvae on the foliage of arborvitae up to a range which greatly exceeded that observed at any of our experimental sites. The incidence of dispersal among neonates emerging on arborvitae was high, as indicated by the high number of larvae captured on sticky traps, and the relatively low number of early instars on arborvitae foliage in relation to the reproductive output of females in the parental generation. The high rate of dispersal among early instars may be due to potential resource depletion over successive generations of bagworms.     

Cytologie de la Pseudogamie chez Luffia lapidella Goeze (Lepidoptera Psychidae)

Summary The bisexual species Luffia lapidella has a pseudogamic (or gynogenetic) form, which is thelytokous and very similar to the parthenogenetic L. ferchaultella, but its egg needs the stimulation of the sperm.The inseminated egg restores its diploid chromosomal number in performing the same kind of restitutional first meiotic division as ferchaultella does. The second division, although already diploid, is normal and is followed by the formation of two nuclei, one of them degenerating as a polar body. The sperm starts developing as in the normal egg, but by metaphase II, it stops growing to a pronucleus and remains as a contracted and pycnotic body. Although attracted by the central female nucleus, it does not fuse with it. The male centriole behaves normally, it possibly plays a role in the first cleavage mitosis. The egg divides diploid and without any paternal chromosomes.

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Travail subventionné par le Fonds National Suisse de la Recherche Scientifique.     

The cytology of parthenogenesis in Solenobia sp. (lichenella L.?) (Psychidae,Lepidoptera)

Sans résumé     

Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)

1. Multiple male copulations can have detrimental effects on female fitness due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are short‐lived and do not feed. Multiple male mating is therefore expected to lead to sperm limitation in females. Sperm limitation and male limitation are hypothesised as causes of the repeated evolution of parthenogenetic reproduction in the Psychidae. 3. In this study, the effects of multiple male mating on female reproduction are investigated in several species of Naryciinae by allowing males multiple copulations. The results for two species, Siederia listerella and Dahlica lichenella, are compared. The sex ratios of 53 natural populations are examined for indications of male limitation. 4. Previous copulations by the male increased the female's risk of remaining unfertilised. However, contrary to expectations, those unfertilised females were capable of successful re‐mating. 5. In S. listerella, the number of previous copulations of males negatively influenced female fitness. Females produced 30% fewer offspring if they mated with a previously mated male. In D. lichenella, the older the male and the lower its number of total lifetime copulations, the higher the female's reproductive success. 6. Only a fraction of the investigated populations had a female‐skewed sex ratio, but differences in development time between males and females could lead to reproductive asynchrony. 7. In conclusion, male mating history did not lead to strong sperm limitation in Naryciinae as had been suggested by their life history.     

Aerial dispersal and host plant selection by neonate Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)

Abstract.  1. Neonate evergreen bagworms, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), disperse by dropping on a strand of silk, termed silking , and ballooning on the wind. Larvae construct silken bags with fragments of plant foliage. This species is highly polyphagous, feeding on more than 125 species of woody plants of 45 families. The larvae commonly infests juniper ( Juniperus spp.) and arborvitae ( Thuja spp.), but rarely feed on deciduous hosts such as maples. The hypothesis is proposed that polyphagy in T. ephemeraeformis is maintained by variation among larvae in dispersal behaviour, and time constraints on the opportunity to disperse, but patterns of host species preference result from a predisposition for larvae to settle on arborvitae and juniper but disperse from other hosts.
2. Consistent with that hypothesis, laboratory experiments revealed: (a) starved larvae varied in their tendency to disperse from paper leaf models; (b) starved larvae readily silked only during their first day; (c) larvae became increasingly sedentary the longer they were exposed to plant foliage; (d) when provided with several opportunities to silk, larvae became sedentary after exposure to arborvitae foliage, but repeatedly silked after exposure to maple ( Acer species) foliage or paper; and (e) larvae were less inclined to silk from foliage of arborvitae than from maple.
3. Field experiments supported the hypothesis by demonstrating that: (a) neonates tended to disperse from maple leaves while larvae older than 1 day tended to settle and remain; and (b) neonates were less likely to disperse from arborvitae and juniper trees than from maples.     

Hierarchical Perception of Stimuli During Case Construction in the Bagworm Moth Eumeta crameri (Lepidoptera: Psychidae)

We studied case construction behavior of bagworm moth, Eumeta crameri (Lepidoptera: Psychidac) in the host plant, Acacia nilotica, at two sites. At the time of the study, Site A had 1-year-old A. nilotica saplings only, whereas Site B had full grown trees. The larva of bagworm moth used either thorns or cut-twigs or both as the materials for building its case. It renovated its case three times, and during each instance it increased the volume of its case by replacing older thorns or cut-twigs by newer and longer ones. However, it exhibited a spectacular predilection for thorns, irrespective of the sites, during the first-instar stage of its development. Thereafter, at Site A it used exclusively cut-twigs, whereas at Site B it preferably used thorns provided they were available in the range of the required length and within the threshold distance. It appears that the bagworm has an ability to process thorn length and distance signals hierarchically to fulfill its priority, that is, case building. Thus it optimizes time and energy expenditures during the period of its larval growth leading to pupation by toggling its preference between thorns and cut-twigs.     

山茱萸蛀果蛾幼虫触角和口器感器的超微形态

【目的】探索寄主范围不同的蛀果蛾科(Carposinidae)幼虫感器之间是否存在差异。【方法】采用扫描电子显微镜观察了为害山茱萸Cornus officinalis Sieb. et Zucc.的单食性蛀果害虫--山茱萸蛀果蛾Carposina coreana Kim老熟幼虫触角和口器感器的超微形态。【结果】山茱萸蛀果蛾幼虫触角柄节未见感器分布, 梗节上有2个刺形感器和3个锥形感器, 鞭节上有1个栓锥感器和3个锥形感器。口器上共有6种感器： 刺形感器数量多, 分布广; 栓锥感器主要分布在颚叶、 下颚须和下唇须上; 指形感器位于内唇和下颚须端节侧缘; 锥形感器和板形感器仅存在于下颚上; 内唇感器为内唇所特有。【结论】蛀果蛾幼虫触角和口器的感器与寄主范围之间未发现严格的对应关系。     

Polyphagy,flightlessness, and reproductive output of females: a case study with bagworms (Lepidoptera: Psychidae)

Abstract 1. We evaluated the relation between plant‐mediated larval traits and the fitness of female bagworms, Thyridopteryx ephemeraeformis Haworth (Lepidoptera: Psychidae) by sampling 29 populations of bagworms on five plant genera (Thuja, Pinus, Picea, Juniperus, and Gleditsia). 2. Compared with those on other genera of plants, female larvae on Thuja attained a larger size at pupation and developed faster. The superior quality of Thuja as a larval food plant resulted in a higher potential fitness of females, as indicated by a low level of pupal mortality and high fecundity. 3. The fecundity of females increased with pupal size on different plant genera, and the effect of host plant genus was negligible compared with pupal size. 4. The mating success of females varied among different populations (0–37% unmated females), but neither host plant, emergence time, nor the size of females had a significant influence on the proportion of mated females. 5. The conversion of adult biomass into reproductive tissue, measured as the ratio between the biomass of eggs divided by the biomass of calling females, increased with the pupal size of females and approached 90% for large females. The high rate of egg conversion in bagworms may be related to the neoteny of short‐lived females that invest little in somatic tissue.     

The structure of the haemocytes of Calpodes ethlius (Lepidoptera)

The haemocytes of Calpodes ethlius are described with the light and electron microscopes. Five fine structurally distinct types are distinguishable. However only three of these, the granular haemocytes, sphaerule cells and oenocytoids can be positively identified using a series of histochemical stains on smears and on thick sections of araldite-embedded material. The classification is based entirely on the structural features even though several suggestions concerning their function can be made from their fine structure. Intermediates having features of more than one cell type suggest developmental relationships.     

The structure of the hemocytes of Galleria mellonella (Lepidoptera)

Four hemocyte types have been identified in the late last larval instar of Galleria mellonella. Plasmatocytoids are round to spindle shaped cells, 10–20 μ long and 5–10 μ wide. The cytoplasm contains no distinguishing inclusions. Golgi complexes, rough endoplasmic reticulum and free ribosomes are abundant. Granular hemocytes are oval shaped cells, 10–20 μ long and 5–10 μ wide. The granules, their most characteristic feature, have a diameter of 0.2 μ, a microtubular sub-structure, and are made up of acidic mucosubstances. Lipid droplets may be present in these cells at some stage of development. These cells appear to be phagocytic. Spherule cells are oval shaped, 15–20 μ long and 5–10 μ wide. The spherules, approximately 2 μ in diameter, have a highly ordered substructure and are made up of acidic mucosubstances. Oenocytoids are the largest cells, 20 by 40 μ. The cytoplasm contains mostly free ribosomes and microtubules.     

园林害虫大袋蛾在四种寄主植物上的繁殖潜能评估(英文)

【目的】大袋蛾Clania variegata是一种严重危害多种植物的食叶性害虫。为了通过合理配植园林植物防治大袋蛾,本研究评估了在悬铃木、月桂、合欢及桃树4种寄主植物上大袋蛾的繁殖潜能。【方法】2018年7月15日至2019年6月21日,在室外纱网隔离环境中测定了大袋蛾分别在悬铃木、月桂、合欢和桃树上的卵期、幼虫期、蛹期、存活率、成虫寿命、雌成虫产卵期和每日单雌产卵量。采用年龄-龄期两性生命表程序TWOSEX-MSChart对大袋蛾发育历期、存活率、成虫寿命及雌虫繁殖力数据进行了分析。【结果】寄主植物种类可显著影响大袋蛾的发育历期和成虫寿命。取食月桂时,大袋蛾2, 3, 4和5龄幼虫的历期显著长于取食其他植物时的;取食桃树时,大袋蛾雌成虫寿命(11.47 d)显著长于取食月桂时的(10.26 d)。大袋蛾取食月桂时的产卵期(7.04 d)显著短于取食悬铃木(7.52 d)、合欢(7.59 d)及桃树(8.11 d)时的。大袋蛾取食悬铃木时的净繁殖力（R₀）(2 015.70粒卵)显著高于取食月桂(1 419.12粒卵)、桃树(1 289.66 粒卵)和合欢(976.67粒卵)时的。大袋蛾取食悬铃木时的内禀增长率(r)(0.02523/d)显著高于取食月桂(0.02377/d)、合欢(0.02304/d)及桃树(0.02194/d)时的。【结论】大袋蛾取食悬铃木时的繁殖潜能显著高于取食月桂、合欢及桃树时的,在园林设计中合理间隔种植月桂、合欢及桃树可能有利于减少大袋蛾对非嗜食植物的危害。     

Postembryonic development of the wing imaginal discs in the female wingless bagworm moth Eumeta variegata (Lepidoptera,Psychidae)

The process of wing disc development and degeneration in the bagworm moth Eumeta variegata was investigated histologically. Morphological differences between two sexes first appear in the penultimate (eighth) larval instar. In the male, wing discs proliferate rapidly in the penultimate larval instar and continue proliferating; a conspicuous peripodial epithelium forms in the last (ninth) larval instar. The hemopoietic organs break down in this stage and disappear completely by the prepupal stage. In the female, in contrast, the wing discs remain as in the previous (seventh) instar, without proliferation of cells inside. No peripodial epithelium forms in the penultimate instar or later. Hemopoietic organs are still attached to the wing discs in the last larval instar and the entire wing discs transform into a plain, thick epidermis in the prepupal period. It is suggested that the hemopoietic organs may prevent the wing discs from developing in E. variegata.     

Genetic Polymorphism and Evolution in Parthenogenetic Animals. II. Diploid and Polyploid SOLENOBIA TRIQUETRELLA (Lepidoptera: Psychidae)

Genic polymorphism at sixteen enzyme loci of four different chromosomal races of Solenobia triquetrella (bisexual, two diploid parthenogenetic races and tetraploid parthenogenetic) has been studied by starch gel electrophoresis. Isolated small diploid bisexual populations have rather uniform allele frequencies at all loci which we have studied. Diploid and tetraploid parthenogenetic individuals of this species are in general as heterozygous as bisexual ones. All parthenogenetic local populations are different from each other in the Alps. These parthenogenetic genotypes cannot be derived from a common ancestor through single mutations but rather bear evidence for a polyphyletic origin of parthenogenesis in Solenobia triquetrella. In the marginal distribution areas of the species in northern Europe single genotypes are spread over far larger areas than in the mountain regions of central Europe. This may be due to the old origin of parthenogenesis and polyploidy in northern Europe. No new parthenogenetic and polyploid strains have lately arisen in the regions outside of the Alps.     

Sex ratio, pupal parasitism, and predation in two declining populations of the bagworm, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae)

Abstract. 1. Two populations of bagworms were censused in Ohio for 6 and 5 years respectively, to determine the influence of major pupal mortality factors. Bagworm densities declined from 2.3 bags per 30 cm of terminal branch to zero.
2. No single key mortality factor was identified in population trends. Parasitic Hymenoptera were common but variable in effect. Avian predation may have been important in reducing one population, while the other was exterminated after a drastic change in sex ratio to favour males.