Instars ofMicroplitis rufiventris [Hym.: Braconidae] and their relative developmental speed under different photoperiods

The internal parasiteMicroplitis rufiventris Kok. passes through 3 instars but moults 3 times within its host. The last moult occuring just at emergence time. The morphology of the egg and larval stages of the parasite are discussed. At 27°C and a photoperiod of 6 h (6L:18D) the endo-developmental cycle of the parasite can summarize as follows: Egg 18–24 h; instar 1,4 days (fighting phase 48 h; feeding phase 30–48 h); instar 2, 12–18 h and instar 3,3 days. The effect of different photoperiods on the relative speeds of the endo-developmental stages of the parasite at each of 30, 25, 20°C were carefully studied. At the first 2 temperatures, the short photoperiod (6L:18D) accelerated the development of larval instars, while both of 18L:6D or 0L:24D slowed down the development. Under the latter photoperiods some larvae failed to moult and had emergence problems. The influence of photoperiod is significantly noticeable at 20°C. The incubation period of the egg-stage was prolonged significantly at 18L:6D and the development of larval instars was significantly faster and refined at 6L:18D. The factor(s) inhibiting the development of the egg-stage perhaps differ from those affecting the larval development. The ventral area of the host mid-gut among malpighian tubes seems to be where the surplus parasite larvae are eliminated by physical attack. A physiologically suppressed parasite larva is able to attack its developed competitor of the same age. Teratocytes cells perhaps play a part in eliminating the surplus parasite larvae by physiological suppression.     

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.     

Factors influencing the developmental capacity of Galleria larval epidermis

The nature of the cuticle secreted by integument from a day-1 penultimate instar larval Galleria when cultured in vivo in the abdomen of a last instar larva varied with the age of the host. When placed in a day-5 last instar larva, the implanted integument secreted a pupal cuticle at the time the host metamorphosed and became a pupa. However, when placed in a day-7 last instar larva the implant, from the same stage donor, secreted a larval cuticle at the time the host pupated. Experimental studies involving implantation of the integument for a 24 hr period, into various developmental stages of normal and ligated last instar larvae, pupae, and pharate adults, prior to placing it in a day-7 last instar larva suggest that a non-hormonal factor present in day-4 and -5 last instar larvae is important to initiate pupal syntheses.     

Physiological aspects of nm-g mutant: An ecdysteroid-deficient mutant of the silkworm,Bombyx mori

We examined physiological and endocrinological properties of the nm-g mutant of the silkworm, whose development was arrested at 1st or 2nd larval instar. The larva of the nm-g homozygote continued to feed and grow past the stage when a normal larva moulted to the next instar. The nm-g larva attained more than twice the body weight of a normal moulting larva, but remained in the same instar with no sign of the moulting until it finally died. The ecdysteroid concentration in the haemolymph of the nm-g larva was reduced and an increase in the titre, which occurred before moulting in the normal larva, was not observed. Injection of 20-hydroxyecdysone induced the nm-g larva to moult and ecdyse to the next larval instar. From these results, we conclude that nm-g is an ecdysteroid-deficient mutant.     

Nutrition of Glossina morsitans: metabolism of U-14C glucose during pregnancy.

A Glossina morsitans female can synthesize alanine, aspartic acid, cystine, glutamic acid, glycine, proline, and serine, and also lipids, from d-[U-¹⁴C] glucose during pregnancy and utilize these products for nourishment of the growing intra-uterine larva. The third instar larva shortly after formation of the puparium can also synthesize these nutrients from glucose and is thus similar to the adult female fly in this respect. It is possible that some glucose taken up by the larva via the maternal uterine glands is converted to the above nutrients. Although the specific nutritional requirements of the growing larva are largely provided by its female parent, the larva has active synthetic systems for the regulation and maintenance of its inherent metabolic steady state. This is reflected in the synthesis of large amounts of glutamic acid in the larva whereas in the adult the emphasis appears to be on the synthesis of proline.Most of the injected glucose and its synthetic products are utilized to provide energy for biosynthetic activity. Uric acid is the main nitrogenous end product of catabolism of non-essential amino acids. A small proportion of such amino acids and glucose are also excreted.Embryonic development which lasts for about 4 days following ovulation is sustained by nutrients within the egg. Following eclosion, the first instar larva begins to feed upon uterine gland secretions. This instar lasts for about 1 day. Ecdysis to the second instar, which lasts for 1 to 2 days, is associated with a three- to fourfold increase in the rate of nutrient uptake. Most rapid feeding begins when the third instar develops. These results are discussed in terms of larval growth in relation to feeding by the adult female parent.     

Developmental strategy of the endoparasite Xenos vesparum (strepsiptera, Insecta): host invasion and elusion of its defense reactions

To successfully complete its endoparasitic development, the strepsipteran Xenos vesparum needs to elude the defense mechanisms of its host, the wasp Polistes dominulus. SEM and TEM observations after artificial infections allow us to outline the steps of this intimate host-parasite association. Triungulins, the mobile 1st instar larvae of this parasite, are able to "softly" overcome structural barriers of the larval wasp (cuticle and epidermis) without any traumatic reaction at the entry site, to reach the hemocoel where they settle. The parasite molts 48 h later to a 2nd instar larva, which moves away from the 1st instar exuvium, molts twice more without ecdysis (a feature unique to Strepsiptera) and pupates, if male, or develops into a neotenic female. Host encapsulation involves the abandoned 1st larval exuvium, but not the living parasite. In contrast to the usual process of encapsulation, it occurs only 48 h after host invasion or later, and without any melanization. In further experiments, first, we verified Xenos vesparum's ability to reinfect an already parasitized wasp larva. Second, 2nd instar larvae implanted in a new host did not evoke any response by hemocytes. Third, we tested the efficiency of host defense mechanisms by implanting nylon filaments in control larval wasps, excluding any effect due the dynamic behavior of a living parasite; within a few minutes, we observed the beginning of a typical melanotic encapsulation plus an initial melanization in the wound site. We conclude that the immune response of the wasp is manipulated by the parasite, which is able to delay and redirect encapsulation towards a pseudo-target, the exuvia of triungulins, and to elude hemocyte attack through an active suppression of the immune defense and/or a passive avoidance of encapsulation by peculiar surface chemical properties.     

Case building behaviour of the caddis fly larva, Lepidostoma hirtum

On hatching from the egg, a larva of Lepidosroma hirtum Curtis constructed a tubular, sand grain case. As the larva became older it periodically added new material to the anterior of the case and, once in every instar except the 1st, cut off ⅓ to ¼ of the posterior of the case. In the 3rd instar the larva changed from adding sand grains to cutting out and attaching almost rectangular leaf panels. By the 5th instar the case was composed entirely of leaf panels. The case was then square in section and composed of one row of panels for each of the sides. The panels were not truly rectangular but convex on the leading edge and sides and concave at the back, so that the anterior convexity of one panel fitted into the posterior concavity of the panel in front. Panels were arranged with their long axes across the case. The seams between panels in the roof were half a panel length out of phase with those in the sides but in phase with those in the floor. The convex sides of a panel allowed it to overlap the seams between panels on the two adjacent sides. If a 5th instar larva was removed from its case it first built a sand grain case followed by a leaf panel case. The animal cut panels from the leaf with its mandibles and then further shaped them by chewing round the edge. Just prior to pupation, the case was modified by the attachment of further panels to the anterior; these included panels which for the first time in the life of the larva were arranged with their long axes along the case.     

Histological reactions of the host induced by the larvae of the warble-fly Oestromyia leporina Pall. (Diptera, Hypodermatidae) (author's transl)

The histological reactions of Mastomys natalensis induced by the larvae of Oestromyia leporina are described from the start of the infection to the complete healing of the evacuated cyst. Against the migrating larva no cellular reactions take place. After the larva settles, the most obvious feature is a non-suppurative inflammation of the surrounding tissue, while a layer of granulation tissue, infiltrated with eosinophils, is built up around the parasite. About 13 days p.i. the number of eosinophils starts to decrease again. No giant cells are present; plasmocytes and lymphocytes are relatively scarce. A few days before the parasite leaves the host, the inner surface of the warble is infiltrated with masses of neutrophils, obviously caused by secondary invasion of bacteria through the warble opening. After the parasite leaves the host, the repair of the tissue takes place within three weeks. The remaining scar tissue contains cells carrying haemosiderin, which disappears entirely about two months later.     

Mandibular glands in the endoparasitic larva of Uropsylla tasmanica Rothschild (Siphonaptera : Pygiopsyllidae)

An histological study of flea larvae was carried out in order to compare free-living, larvae with the unique endoparasitic larva of Uropsylla tasmanica Rothschild (Siphonaptera : Pygiopsyllidae), a species confined to dasyurid hosts in Tasmania and Victoria, Australia. The free-living species examined were Ctenocephalides felis Bouché (Siphonaptera : Pulicidae) and Odontopsyllus quirosi Gil Collado (Siphonaptera : Leptopsyllidae). Mandibular glands are present in 1st and 3rd instar U. tasmanica, but are absent from 2nd and 3rd instar O. quirosi and all larval instars of C. felis. Such glands in flea larvae have not beeb described previously and they appear to be unique to the endoparasitic U. tasmanica larva. Their presence during the 3rd instar as well as in the 1st instar suggests that although it is possible they play a role in the initial penetration of host skin by the newly hatched larva, they are active in secretion also during the time when the larvae are feeding on host tissue within the dermis.     

An ultrastructural study of the response of Blatella germanica (Orthoptera: Blattidae) to the nematode Abbreviata caucasica (Spirurida: Physalopteridae)

An ultrastructural study of the response of Blatella germanica (Orthoptera: Blattidae) to the nematode Abbreviata caucasica (Spirurida: Physalopteridea). International Journal for Parasitology4: 133–138. This study investigates the response of the roach, Blatella germanica L. to the invading spirurid nematode, Abbreviata caucasica v. Linstow. Soon after the first stage nematodes entered the epithelial cells of the colon wall, the surrounding host cells broke down into syncytial giant cells. Large polychromatic epithelial cell nuclei occurred throughout the giant cells and the nematodes moved freely within the cytoplasmic matrix. These giant cells were in turn surrounded by blood cells responding to the disruption. The nematodes developed to the infective third stage juveniles within the giant cells and ingested the syncytial cytoplasm. After reaching the third stage, the parasites remained in a quiescent state within the vacuolated cell which was surrounded by a double tissue layer.Evidence indicated that successful development of the parasite was dependent on the disrupted epithelial cells forming a giant syncytial cell which protected and supplied nourishment to the parasite.     

Natural enemies ofAcraea terpsicore [Lep.: Nymphalidae] in ghana,with particular reference to the parasiteCharops diversipes [Hym.: Ichneumonidae]

The arthropod parasites and predators ofAcraea terpsicore (L.) were determined in the forest zone of Ghana. An unidentified mite was predatory on the very young larvae. The pentatomidsPlatynopus rostratus Dru. andMacrorhaphis acuta (Dall.) were also predatory on the larvae.Telenomus sp. parasitized the eggs. The tachinidCarcelia normula (Curran) and the ichneumonidCharops diversipes Roman were parasitic on the larvae.C. diversipes was hyperparasitized by the chalcididBrachymeria feae Masi and the eulophidPediobius taylori Kerrich. Laboratory tests showed that parasitism ofA. terpsicore byC. diversipes was significantly highest in the 1st instar, followed by the 2nd, 3rd and 4th. The 5th instar was not parasitized. These results seemed to reflect both host susceptibility and parasite preference. Only a singleC. diversipes larva developed in a host. The developmental period of the parasite egg and larva varied inversely with the age of the host at which it was parasitized. A femaleC. diversipes could oviposit immediately after emergence.     

Dynamic expression pattern of kinesin accessory protein in<Emphasis Type="Italic">Drosophila</Emphasis>

We have identified theDrosophila homologue of the non-motor accessory subunit of kinesin-II motor complex. It is homologous to the SpKAP115 of the sea urchin, KAP3A and KAP3B of the mouse, and SMAP protein in humans.In situ hybridization using a DmKAP specific cRNA probe has revealed a dynamic pattern of expression in the developing nervous system. The staining first appears in a subset of cells in the embryonic central nervous system at stage 13 and continues till the first instar larva stage. At the third instar larva stage the staining gets restricted to a few cells in the optic lobe and in the ventral ganglion region. It has also stained a subset of sensory neurons from late stage 13 and till the first instar larva stage. The DmKAP expression pattern in the nervous system corresponds well with that of Klp64D and Klp68D as reported earlier. In addition, we have found that the DmKAP gene is constitutively expressed in the germline cells and in follicle cells during oogenesis. These cells are also stained using an antibody to KLP68D protein, but mRNAin situ hybridization using KLP64D specific probe has not stained these cells. Together these results proved a basis for further analysis of tissue specific function of DmKAP in future.     

Larva of the leaf beetle Labidostomis longimana (Coleoptera, Chrysomelidae, Clytrinae)

The first- and the last-instar larvae of the leaf-beetle Labidostomis longimana are described in detail for the first time. The last instar larva is morphologically close to L. sibirica larva and differs from it in the absence of a projection in the medial emargination of the labrum, in the presence of 7 spiniform setae on the tibiotarsus ventrally, 11–13 narrow simple setae on the tibiotarsus dorsally, and fine rugae on the larval case.     

Description of the larva and pupa of Parnops glasunovi (Coleoptera, Chrysomelidae)

The last instar larva and pupa of Parnops glasunovi Jcbs. are described for the first time. A key to genera of the subfamily Eumolpinae from Middle Asia is given.     

The eupyrene-apyrene dichotomous spermatogenesis of Lepidoptera. The relationship with postembryonic development and the role of the decline in juvenile hormone titer toward pupation.

The relationships between the stages of postembryonic development and the occurrence of eupyrene and apyrene spermatogenesis, and the effects of the decline of the juvenile hormone (J.H.) titer toward pupation in these processes, were studied in the carob moth, Ectomyelois ceratoniae. The accurate timing of the spermatogenetic events was determined daily from the 2nd instar larva to the imago in squashes and electron microscope preparations of testes. Eupyrene spermatids elongate in two phases. In the first, beginning in late 4th instar larva, only flagella elongate, while in the second, beginning in the mid 5th instar larva, both flagella and nuclei elongate. Apyrene spermatogenesis starts just after the beginning of the nuclear elongation of eupyrene spermatids, in the mid 5th instar larva and not in the pupa, as is commonly believed. Using ligatures, topical applications of a J.H. mimic, and testes transplantation, it was found that the nuclear elongation begins in the 5-day-old eupyrene spermatid and cannot be induced earlier; the elongation is inhibited by high titer of the J.H. mimic. Elongation of the flagella, however, is unaffected by fluctuations of the J.H. titer. The onset of the apyrene spermatogenesis, which occurs in the very early 5th instar larva or before, was found to be unrelated to the decline in the J.H. titer toward pupation.     

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation was assessed in the laboratory. In the first experiment, a first instar of one of the two above species was kept with a fourth instar of the other species in a Petri dish. The number of times each first instar larva was encountered by the fourth instar larva and the fate of the first instar was determined over a period of 10 min. The fourth instar larvae captured and killed all the first instar larvae of their own species at the first encounter. However, when presented with fourth instar larvae of the other species the first instar larvae of A. bipunctata and H. axyridis were encountered 6.4 ± 1.3 ( n  = 10) and 19.4 ± 2.1 ( n  = 10), respectively. In this experiment no first instar larvae of H. axyridis , whereas all those of A. bipunctata , were killed.     

Pectinase and plant growth-promoting factors in the salivary glands of the larva of the bug,Lygus disponsi

Pectinase was detected in the salivary gland of the larvae of Lygus disponsi. The pectinase activity per bug may increase gradually from the first instar larva to the adult. The salivary gland of the third instar larva contained substances indirectly promoting plant growth, i.e. the factor promoting the activity of 3-indoleacetic acid (IAA) or the factor inhibiting the activity of IAA-oxidase, whereas those of the fourth and 5th instar larvae seemed to contain, in addition, auxins which directly promote plant growth. Larvae of all instars had a significant promoting factor only in fraction III of the salivary gland solution. The larvae are as toxic as the adults to sugar beet plants. The presence of pectinase and plant growth-promoting factors in the salivary gland is compared among mirid bugs, and their significance is discussed.