Parasitism of Western Corn Rootworm Larvae and Pupae by Steinernema carpocapsae

Virulence and development of the insect-parasitic nematode, Steinernema carpocapsae (Weiser) (Mexican strain), were evaluated for the immature stages of the western corn rootworm, Diabrotica virgifera virgifera LeConte. Third instar rootworm larvae were five times more susceptible to nematode infection than second instar larvae and 75 times more susceptible than first instar larvae and pupae, based on laboratory bioassays. Rootworm eggs were not susceptible. Nematode development was observed in all susceptible rootworm stages, but a complete life cycle was observed only in second and third instar larvae and pupae. Nematode size was affected by rootworm stage; the smallest infective-stage nematodes were recovered from second instar rootworm larvae. Results of this study suggest that S. carpocapsae should be applied when second and third instar rootworm larvae are predominant in the field.     

MASS PREPARATION OF NUCLEI FROM THE LARVAL SALIVARY GLANDS OF DROSOPHILA HYDEI

A method has been developed for isolating gram quantities of salivary glands from late third instar larvae of Drosophila hydei. The isolated glands have a normal appearance and incorporate RNA and DNA precursors normally. Nuclei can be isolated from these glands in 90% yield with the use of detergents. These nuclei contain morphologically normal giant polytene chromosomes.     

TnaA,an SP-RING Protein,Interacts with Osa,a Subunit of the Chromatin Remodeling Complex BRAHMA and with the SUMOylation Pathway in Drosophila melanogaster

Tonalli A (TnaA) is a Drosophila melanogaster protein with an XSPRING domain. The XSPRING domain harbors an SP-RING zinc-finger, which is characteristic of proteins with SUMO E3 ligase activity. TnaA is required for homeotic gene expression and is presumably involved in the SUMOylation pathway. Here we analyzed some aspects of the TnaA location in embryo and larval stages and its genetic and biochemical interaction with SUMOylation pathway proteins. We describe that there are at least two TnaA proteins (TnaA₁₃₀ and TnaA₁₂₃) differentially expressed throughout development. We show that TnaA is chromatin-associated at discrete sites on polytene salivary gland chromosomes of third instar larvae and that tna mutant individuals do not survive to adulthood, with most dying as third instar larvae or pupae. The tna mutants that ultimately die as third instar larvae have an extended life span of at least 4 to 15 days as other SUMOylation pathway mutants. We show that TnaA physically interacts with the SUMO E2 conjugating enzyme Ubc9, and with the BRM complex subunit Osa. Furthermore, we show that tna and osa interact genetically with SUMOylation pathway components and individuals carrying mutations for these genes show a phenotype that can be the consequence of misexpression of developmental-related genes.     

Cell cycle and DNA content of mitotic cells in brain ganglia ofdrosophila larvae

The programmes of replication of hetero- and euchromatin regions, mitotic cell cycle and the DNA content in metaphases in brain ganglia from late third instar larvae ofDrosophila melanogaster (wild type and a tumour bearing mutant, 1(2)gl, strain) and ofDrosophila nasuta were examined by autoradiography of [³H]thymidine labelled (continuous or pulse) cells and by cytophotometry, respectively. Brain ganglia labelled continuously with [³H]thymidine for 24 hin vitro showed a significantly high proportion of cells with incorporation of radioactivity restricted to heterochromatin only. Pulse labelling of brain ganglia from larvae ofDrosophila melanogaster andDrosophila nasuta followed by chase for different time intervals showed that (i) the frequency of labelled metaphases was more than 50% within 15 to 30 min of chase and remained higher than 50% in nearly all the chase samples till 24 h, (ii) euchromatin labelled metaphases appeared with a low frequency within 1 to 4 h chase period but the heterochromatin labelled metaphases continued to be more common in the later chase samples also, (iii) single chromatid labelled second cycle metaphases were seen within 1 to 4 h after the pulse, but their frequency did not increase in the later samples. Cytophotometry of feulgen-DNA and Hoechst 33258 stained metaphases in late third instar larval brain ganglia revealed a greater variation in the DNA content of individual metaphases, although the means were close to the expected 4 C content. It appears that in relation to the known asymmetric cell divisions of neuroblast and other neural cells, the mitotically active cells in brain ganglia comprise a heterogenous population with widely varying lengths of the different phases of cell cycle; some of them may not cycle regularly and may possibly have a discontinuous S-phase.     

Prey stage preference and feeding behaviour ofOligota kashmirica benefica (Coleoptera: Staphylinidae), an insect predator of the spider miteTetranychus urticae (Acari: Tetranychidae)

We studied the prey stage preference and feeding behaviour of the first to third instar larvae and adult females ofOligota kashmirica benefica Naomi (Coleoptera: Staphylinidae), a predator of the spider miteTetranychus urticae Koch (red form) (Acari: Tetranychidae), on leaves of the kudzu vine (Pueraria lobata (Wild.) Ohwi (Leguminosae)) under laboratory conditions. The number of mites eaten increased with the growth of predator larvae. Third instar larvae preyed on all stages of spider mite, whereas first instar larvae preyed mainly on immobile stages (eggs and quiescent stages). The predator larvae showed two types of foraging behaviour (active searching and ambush behaviour) when targeting the mobile stages (larval nymph and adult stages of prey). Although no difference was found in the number of prey consumed by adult females and third instar larvae of the predator, the adult females mainly attacked and consumed the immobile stages.     

Diapause and development in the tobacco budworm,Heliothis virescens: A comparison of haemolymph ecdysteroid titres

The signal to induce diapause in H. virescens comes early in development (prior to the third instar in most insects), but the signal to break diapause can come shortly after entrance into diapause at pupation. Haemolymph ecdysteroid titres in both diapause-bound and non-diapause-bound Heliothis virescens larvae were similar in the first two thirds of the last-larval instar, when similar changes in morphology and behaviour occurred. However, the number of stepwise increases in titre and the timing of the steps was different in the two groups of larvae. Haemolymph ecdysteroid titres in the last third of the instar were approx, five times higher in non-diapause than in diapause-bound larvae. In diapausing pupae, haemolymph ecdysteroid titres dropped to levels found in larvae which had completed two thirds of the last instar. When diapausing pupae were warmed to break diapause, haemolymph ecdysteroid titres rose again. However, 2 of the 4 high ecdysteroid levels detected in pupae developing after diapause break were considerably lower than those detected for non-diapause pupae.     

The effects of pH,phenol, and sodium chloride on survival and caloric,lipid, and nitrogen content of a laboratory population of chironomus attenuatus (Walk.)

Continuous flow, laboratory microcosms were used to measure the effects of pH, phenol, and NaCl on the survival of the life stages of Chironomus attenuatus, the caloric content of third and fourth instar larvae and adults, the lipid and protein-nitrogen content of fourth instar larvae, and the interaction among the various responses. The metabolism of phenol was studied using uniformly labeled phenol-C¹⁴. pH had a significant effect on the survival of all life stages of C. attenuatus. Survival was higher for all larval instars at pH 7.2 while adult emergence was higher at pH 6.2. Increasing phenol levels resulted in a nearly linear increase in caloric content. Sodium chloride affected the lipid content of fourth instar larvae. The lipid content was higher with NaCl present in the media than without NaCl. Interaction had a significant effect on all responses except survival of third and fourth instar larvae. Phenol-C¹⁴ was metabolized by bacteria, but not by C. attenuatus.     

The effects of host age and superparasitism by the parasitoid, Microplitis rufiventris on the cellular and humoral immune response of Spodoptera littoralis larvae

To study the dynamics of stage-dependent immune responses in Spodoptera littoralis (Boisd.) larvae (Lepidoptera: Noctuidae), single and superparasitism experiments were carried out using the parasitoid Microplitis rufiventris Kok. (Braconidae: Hymenoptera). Compared to younger (preferred) host larvae, the older (non-preferred) host larvae displayed a vigorous humoral response that often damaged and destroyed the single wasp egg or larva. Superparasitism and host age altered both the cellular and humoral immune responses. Younger host larvae showed a stronger encapsulation response compared to older host larvae. Moreover encapsulation rates in younger hosts (e.g., second instar) decreased with increasing numbers of parasitoid eggs deposited/larvae. In older larvae, the encapsulation rate was low in fourth, less in fifth and absent in sixth instar hosts. Conversely, the order and magnitude of the cellular immune response in S. littoralis hosts were highest in second instar larvae with the first instar larvae being a little lower. The immune response steadily decreased from the third through to the fifth instar and was least obvious in the sixth instar. In contrast, the general humoral immune response was most pronounced in sixth instar larvae and diminished towards younger stages. The results suggest that both cellular and humoral responses are stage-dependent. Wasp offspring in younger superparasitized host larvae fought for host supremacy with only one wasp surviving, while supernumerary wasp larvae generally survived in older superparasitized larvae, but were unable to complete development. Older instars seem to have a method for immobilizing/killing wasp larvae that is not operating in the younger instars.     

Alterations in the production of hemocytes due to a neoplastic mutation of Drosophila melanogaster

The hemocytes of a genetically induced, temperature-sensitive lethal mutation of Drosophila, Tum¹, were examined both quantitatively and qualitatively during the third larval instar. At the tumor-permissive temperature, 29°C, there was a fourfold increase in the concentration of circulating hemocytes in mutant larvae as compared to control. Additionally, the relative frequency of lamellocytes was 30 times greater in Tum¹ larvae than Basc in the early third instar. However, the severity of this abnormality gradually diminished as Tum¹ approached pupariation; though high frequencies of lamellocytes were always present. At the tumor-restrictive temperature (15°C) the concentration of circulating hemocytes was over twice that found at 29°C for Tum¹ larvae, and did not change during the course of third instar. However, in contrast to 29°C there was no abnormal increase in the frequency of lamellocytes at the tumor-restrictive temperature. Control larvae had equivalent concentrations of hemocytes at both temperatures. In one of two temperature shift experiments, Tum¹ larvae shifted from 15° to 29°C at the beginning of third instar expressed the abnormal hemocyte concentration and differentiation associated with larvae raised continuously at 29°C. In addition, Tum¹ larvae shifted from 29° to 15°C expressed reduced abnormalities of hemocyte differentiation, e.g., with fewer lamellocytes in circulation. The possibility of a temperature-sensitive period for the activation of the Tum¹ gene is discussed.     

Effect of cold acclimation and rapid cold-hardening on the survival of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) under cold stress

Spodoptera frugiperda is a highly invasive pest species that recently invaded Africa and Asia causing severe economic losses, primarily related to corn and rice crops. Temperature is one of the most important environmental factors that influence the invasion of pests into new habitats. However, little is known regarding the thermal tolerance characteristics of invasive S. frugiperda. Thus, we investigated the response of four developmental stages of S. frugiperda (i.e., eggs, third and sixth instar larvae, and pupae) to cold acclimation (CA) and rapid cold-hardening (RCH). All individuals suffered high mortality with 24-h temperature treatments at <?5°C and >35 °C. The CA treatment significantly increased the survival rate of the eggs and third instar larvae, although it did not affect the sixth instar larvae and it decreased the pupation rate. The RCH treatment at 5 °C for 5 h or 2 °C for 2 h increased the cold tolerance capabilities of the third and sixth instar larvae, respectively. Thus, the larval stage appears to be crucial for the cold tolerance of S. frugiperda. Our findings improve the current understanding of the cold tolerance characteristics of S. frugiperda and indicate its potential for survival in the newly invaded temperate regions of Asia.     

Morphological study on the immature stages of the Banana fruit caterpillar,Tiracola plagiata (Walker, 1857) and its close relative,Tiracola aureata Holloway, 1989 (Noctuidae: Noctuinae: Leucaniini) with their host plant information

Imature stages of the Banana fruit caterpillar, Tiracola plagiata (Walker, 1857) and its close relative, Tiracola aureata Holloway, 1989 are described and illustrated. We revealed the following four facts. 1: The sixth instar is estimated to be the last instar larvae in both species based on the width of head capsules. 2: Morphologically they are distinguishable in the third to sixth instar larvae, but not distinguishable in the eggs, first to second instar larvae and pupae by our study. 3: Both species are polyphagous. 4: Some of the formerly known host plant records of T. plagiata should be excluded because they are revealed to be the hostplants of T. aureata.     

The control of prepupal puffing patterns in vitro; Implications for prepupal ecdysone titres in Drosophilia melanogaster

In late third instar larvae and prepupae of Drosophila melanogaster there is a complex change in puffing patterns in the salivary gland chromosomes. There are two peaks of activity in this period. The first, in larvae, is known to be under the control of the moulting hormone ecdysone. The second, in prepupae, is now shown by the in vitro culture of prepupal glands to be under the specific control of β-ecdysone in a manner similar to the first. A new class of puffs, active between these two peaks, whose induction is inhibited by ecdysone in vitro, is described. The behaviour of these puffs, exemplified by 75CD and 63E, suggests a period of very low ecdysone titre in vivo. The developmental significance of the role of ecdysone during prepupal development is discussed.     

Field application of a Streptococcus causing brachyosis in larvae of Porthetria dispar

A motile strain of Streptococcus faecalis originally isolated from a naturally infected larva and tested for pathogenicity under laboratory conditions was tested in the field. Mistblower sprays prepared from broth cultures induced brachyosis in gypsy moth larvae feeding in apple trees. One application was made against larvae in late second, early third instar, and a second application was tested against larvae in the fourth instar. The test demonstrated the ability of the bacterium to produce disease and prevent defoliation even in an area with a heavy population.     

Effect of Host Plant on the Infectivity of Sl MNPV to Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) Larvae

The susceptibility of Spodoptera litura to SlMNPV infection was markedly affected by phyto-chemicals ingested during the acquisition of viral inoculum on foliage of tomato and cauliflower. The LD₅₀ values computed for second, third and fourth instar larvae assayed on tomato leaves were 254, 819 and 23395 PIBs/larva, respectively whereas, it was 326, 1719 and 43843 PIBs/larva for respective instars when assayed on cauliflower leaves. Thus LD₅₀ values for second, third and fourth instar larvae were 1.28-, 2.09- and 1.87- fold lower, respectively in tomato leaves. Similarly, LT₅₀ values for second, third and fourth instar larvae assayed on tomato leaves were 7.1 and 7.5 days, respectively at inoculum dose of 2.7×10⁴ PIBs/larva whereas, it was 7.7 and 8.0 days for respective instars when assayed on cauliflower leaves at same inoculum. This result also showed that the S. litura were more susceptible on tomato leaves in comparison to cauliflower leaves as the time required for mortality was lower in tomato leaves. The possible biochemical bases for differential level of mortality of S. litura larvae on tomato and cauliflower crops needs to be investigated.     

Cell differentiation during the ontogeny of larval salivary glands of the fly, Telmatoscopus albipunctatus

Using the larvae, pharate pupa, and pharate adults of the moth fly, Telmatoscopus albipunctatus, histological and ultrastructural features of the salivary glands were investigated. The gland lumen contains a milky secretion from the first instar. This secretion continues to ccur at all subsequent developmental stages; with the onset of the pharate pupal stage, however, the secretion becomes transparent and rather viscous. Histochemical tests revealed that it is mainly proteinaceous. Glands from the same developmental stage may respond differently to PAS-reaction.Various cell organelles were compared at consecutive stages of larval development and of secretory activity of the salivary glands. In first and second instar larvae autophagic vacuoles are virtually absent in the salivary gland cells. They were occasionally found in the third instar, when they appear to be engaged in the process of organelle turnover. Histolysis of the larval glands is initiated towards the close of the fourth instar when the number of autophagic vacuoles starts to increase. Simultaneously, the cytoplasm, previously full of ribosomes and endoplasmic reticulum, starts losing these structures. At the beginning of the pharate adult stage, the cytoplasm becomes practically devoid of all structures other than those engaged in autophagy.Polyteny of the chromosomes during ontogeny of the larval salivary glands is also discussed.     

室内测定6种化学杀虫剂对草地贪夜蛾幼虫的毒力

2019年草地贪夜蛾Spodoptera frugiperda入侵我国多个省份和地区,对我国农业生产造成重大影响。化学防治是应对入侵害虫的主要措施,因此,本研究测定了6种不同作用机制杀虫剂对草地贪夜蛾初孵和3龄幼虫的生物活性。结果表明,对初孵幼虫具有较高毒力作用的为氯虫苯甲酰胺、多杀菌素、茚虫威、阿维菌素和甲氧虫酰肼;对3龄幼虫具有较高毒力作用的为氯虫苯甲酰胺、多杀菌素和茚虫威;与初孵幼虫相比,阿维菌素、茚虫威、多杀菌素和甲氧虫酰肼的LC 50分别提高了78.06、1.70、11.73和23.09倍。本研究筛选出了对草地贪夜蛾初孵幼虫和3龄幼虫杀虫效果较好的药剂,证明了低龄幼虫对部分农药抵抗力较弱,而3龄后的幼虫抵抗力显著增加,为田间草地贪夜蛾的化学防治提供了科学的用药指导。     

Competence of Macrotermes michaelseni (Isoptera: Macrotermitinae) larvae to differentiate into soldiers under the influence of juvenile hormone analogue (ZR-515, methoprene)

It has been shown that only third instar larvae of Macrotermes michaelseni have the competence to differentiate into presoldiers under the influence of juvenile hormone analogue (JHA). The timing of events leading to presoldier formation was independent of JHA dose above the threshold. Further studies with homogeneous groups of third instar larvae of different ages showed that only larvae of a certain age (0–6 days) could respond to topically applied JHA to produce presoldiers and intercastes (intermediate forms). Older larvae did not respond, hence, 0–6 days interval is the competence period for presoldier differentiation in this species. It seems also that the corpora allata of those individuals which differentiate into presoldiers become activated during the competence period, possibly by the parents or other means.     

The time--mortality response of mosquito larvae infected with the fungus Culicinomyces

In laboratory experiments with Culicinomyces, the time of death of infected Anopheles hilli larvae decreased as the concentration of conidia to which they were exposed increased. At a concentration of 10³ conidia/ml, most first instar and third instar larvae died later than 2 days after exposure and the majority of dead specimens developed external sporulation on the exterior cuticle. On the other hand, at a concentration of 10⁵ conidia/ml, more than 60% of first and third instar larvae died within 2 days of exposure. Very few of these larvae developed external sporulation and it appears that most of them died after penetration by the fungus through the gut cuticle but before the hemocoel was colonized by mycelium. The reason for this rapid death at high concentrations of inoculum is not known, but it is thought that it may be caused by toxic substances associated with the invading hyphae which only attain a lethal titer when massive invasion originates from large numbers of conidia.