The parasites of the psyllidae—3. Some notes on the biology and host relationships of Parapsyllae-Phagus Adulticolus Robinson (Hymenoptera)

Abstract

Parapsyllaephagus Adulticolus Robinson (CHALCIDIDAE: Encyrtinae) is an endoparasite of the adults of Psylla melanoneura Förster and Psylla subferrigenea Edwards. The life histories and biology of the hosts and parasite are described. Parapsyllaephagus adulticolus has five larval instars, which feed selectively upon the developing internal genitalia of the host at first, and eventually, as the final instar, upon the whole of the abdominal viscera. Pupation within the psyllid is followed by emergence of the adult parasite through the posterior dorsal surface of the abdomen of the host. The effect of these activities upon the migration of the adult psyllid from a winter shelter plant to a summer host plant is discussed and a relationship between the stimulus to migrate and the state of development of the internal genitalia is postulated. Some aspects of the orientation of the parasite larva within the host and the phenomenon of larval reversal are discussed.     

The preimaginal stages of Minotetrastichus frontalis (Nees) and Chrysocharis laomedon (Walker) (Hymenoptera: Eulophidae), parasitoids associated with Phyllonorycter issikii (Kumata) (Lepidoptera,Gracillariidae)

The biology and morphology of the early larval instars of Minotetrastichus frontalis (Nees) are redescribed and the morphology of the preimaginal stages of Chrysocharis laomedon (Walker) (Hymenoptera: Eulophidae) are described in detail for the first time. Both species are larval-pupal parasitoids of Phyllonorycter issikii (Lepidoptera, Gracillariidae), which is associated with Tilia sp. The female of M. frontalis lays her egg beside the host larva and the newly hatched first instar larva moves and has to find the host larva. The larva of P. issikii tries to continue its feeding but never pupates after paralysis. The female of C. laomedon lays its egg inside the cuticle of the larva of P. issikii, but the newly hatched parasitoid larva vacates the host larva and develops externally on its surface as an ectoparasitoid. Such behaviour might be facilitated by the constant temperature and humidity inside the mine. Some peculiarities of parasitoid–host relationships are described and discussed.     

Larval instars of the ant Strumigenys solifontis Brown (Hymenoptera: Formicidae): the fallacy of size distribution

Larval instars of the myrmicine ant Strumigenys solifontis Brown were determined by measuring the head width under a stereomicroscope and examining the morphology, especially chaetotaxy, by light microscopy and scanning electron microscopy. This study found that the larval stage consisted of four instars, but the first and second instars were not distinguishable by their head widths. However, the four instars could be discriminated clearly by a combination of size measurement and observations on the chaetotaxy. Within a population, there are few larvae in the first instar because of its short period (only 1–2 days before moulting into the second instar) and the low oviposition rate of the queen. Therefore, the first-instar larva needs to be collected separately from other instars so that it is not missed.     

An Australian stiletto fly (Diptera: Therevidae) parasitised by a bee fly (Diptera: Bombyliidae)

Exechohypopion therephaga sp. nov. (Bombyliidae) emerged from the pupa of Parapsilocephala ambocerina sp. nov. (Therevidae) collected near Wentworth, New South Wales, Australia. The adults, pupae and mature larvae of the bombyliid and therevid are described and illustrated. Because the therevid host was collected from soil as a larva, the first instar bombyliid planidium is presumed to attach to the therevid in the larval stage. This is the second known record of a therevid being parasitised. Both known cases occurred in Australia and involved a bombyliid parasitoid.     

The use of epiphylls as larval hostplants by the neotropical riodinid butterfly,Sarota gyas

The neotropical riodinid butterfly Sarota gyas is shown to utilize non-nitrogen fixing epiphylls as larval hostplants. The host substrate where the epiphylls grow appears unimportant to oviposition by adults or feeding by larvae. The larva of S. gyas is described and the use of long setae as a defense by amymecophilous riodinids is discussed.     

A new species of Cerchysiella (Hymenoptera: Encyrtidae) parasitic in larva of chestnut trunk borer (Coleoptera: Cerambycidae) from China with notes on its biology

A new species of Cerchysiella Girault (Hymenoptera: Chalcidoidea, Encyrtidae), Cerchysiella raddeii Yang, sp. nov., is described from China. It is a gregarious koinobiont endoparasitoid in mature larvae of the chestnut trunk borer, Massicus raddei (Blessig) (Coleoptera: Cerambycidae), a serious pest which causes severe damage to many oak tree species, particularly Quercus mongolica and Quercus liaotungensis (Fagaceae) in forested areas of northeastern China. The new species is one of the principal natural enemies of the wood borer and it has high potential as a biological control agent with parasitism rates of 6.7%, large numbers of adult wasps were reared from a single host larva (average 1083.8), and there is a high female : male sex ratio (9.67 : 1).     

Do caterpillars of Dryas iulia alcionea (Lepidoptera,Nymphalidae) show evidence of adaptive behaviour to avoid predation by ants?

Plants bearing extrafloral nectaries can attract wasps, bugs, and mainly ants. Ants can defend plants against herbivores by treating the plant as an extension of their own territory. We evaluated the efficiency of resting sites built by Dryas iulia alcionea larvae as protection against ant predation on their host plant Passiflora suberosa. The results showed that ants on P. suberosa have significant influence on the survival of D. iulia caterpillars. The use and construction of resting sites was recorded through the fourth larval stadium. A strong inverse relationship between the number of resting sites constructed per larva and the developmental stage of the larvae was observed. Additional results suggest that the efficacy of resting sites against cursorial predators decreases with larval development. The behaviour of constructing resting sites probably evolved by natural selection. It is likely that this behaviour was important for the ancestral lineage that gave origin to Heliconiinae genera Dryas, Dryadula and Phylaethria.     

The complete larval development of the crab Pilumnus spinifer (Brachyura: Xanthoidea: Pilumnidae) reared in the laboratory

The complete larval development of the crab Pilumnus spinifer from the western Mediterranean was obtained in the laboratory. All four zoeal stages and the megalopa are described and illustrated. The morphological characters of the larvae of Pilumnus spinifer are compared with those of other known larvae of the genus. The zoeae of P. spinifer show the rostral spine longer than the antennule (excluding aesthetascs); short lateral spines present on the carapace, and the mediolateral processes are present only in abdominal somites 2 and 3. The megalopa is similar to that of other Pilumnidae species. The morphology of the larval stages shows very similar characteristics to that of those of P. hirtellus and P. dasypodus, among the described stages of the family.     

Intraspecific larval aggression in two species of Hyperini (Coleoptera: Curculionidae)

Two unusual types of behaviour (wandering and intraspecific aggressive behaviour) have been observed when rearing larvae of two species of the tribe Hyperini. Wandering of Hypera postica in search for food was observed in L1, L2 and L3 larvae, as well as in young L4 larvae. L1 larvae also disperse in response to crowding. Wandering of L2 to young L4 instars was a response to food shortage. Wandering of late L4 larva (‘prepupa’) occurs because of searching for a place to spin the cocoon and pupate. Encounters between the larvae may result in agonistic behaviour, and some larvae may die as a consequence of fighting. This aggression increases with food limitation. Agonistic intraspecific behaviour has not been described to date in weevil’s larvae and it probably may not occur under natural conditions when there is a plenty of food and larval densities are decreased by pathogens or parasitoids.     

Morphology and feeding behaviour of the leaf-mining larva of Cheilosia semifasciata (Diptera: Syrphidae)

In North Wales the larva of Cheilosia semifasciata (Diptera: Syrphidae) makes full-depth blotch mines in leaves of Umbilicus rupestris. Mines occur mostly on shaded plants with one larva per plant. Each larva mines several leaves to complete development and initiates new mines by curling round the leaf margin and puncturing the epidermis under the leaf. Unlike other dipteran leaf-miners which feed on their sides, only the thorax is turned sideways when feeding. The larva uses a grasping organ on the anal segment to grip the substrate when moving externally on the food-plant. Inside leaf mines, position is further secured by the integumental vestiture which grips the epidermis above the larva. The morphology and behaviour of the larva of C. semifasciata differs markedly from larvae of three congeneric species that tunnel in stems and roots.     

The biology and immature stages of Thrybius togashii Kusigemati (Hymenoptera: Ichneumonidae: Cryptinae), with a description of the male

Thrybius togashii Kusigemati is found to be an ectoparasitoid of larvae of a phytophagous eurytomid, Tetramesa sp. (Hymenoptera), growing gregariously in internodal cavities of reeds (Phragmites japonica Steud.), in Japan. The female of T. togashii oviposits into reed canes and its predaceous larva consumes almost all eurytomid larvae in an internodal cavity. This species is bivoltine. The mode of parasitism of this species is unique in some respects. First, when the female oviposits, no food resources are available in the reed. Second, the parasitoid allows part of the host larvae to grow and exploits increasing food resources. The egg, pupa and first to final instar larvae and adult male are described and figured for the first time. Colour dimorphism in both sexes and adult morphology adapted to habitat and ovipositional substrate are also discussed.     

Biology and immature stages of Panteles schnetzeanus (Hymenoptera: Ichneumonidae), a parasitoid of Lampronia fuscatella (Lepidoptera: Incurvariidae)

Panteles schnetzeanus (Roman), a parasitoid of the gall‐forming incurvariid moth Lampronia fuscatella (Tengström) and currently placed in the Stilbopinae, is shown to be a solitary koinobiont larval endoparasitoid. The large dark‐pigmented eggs possess a hook‐like tail which is embedded in host tissue, typically at the posterior or anterior end of the host. In cases of superparasitism, which represented 70% of cases, only a single egg hatches. The first instar, prepupa and final larval instar head capsules are described and illustrated. Many differences between the biology of Panteles and of Stilbops are discussed. Circumstantial evidence that suggests that Panteles may have an alternative host is also presented based on the emergence dates for it and the Lampronia together with the size, number and placement of the Panteles eggs. DNA sequence data additionally provide the first record of a eupelmid as attacking a gall‐forming incurvariid/parasitoid system, though it is not clear whether this was an hyperparasitoid on the Panteles or a primary on the incurvariid.     

Studies on Gasteroclisus rhomboidalis (Boheman.) (Coleoptera: Curculionidae)—a pest of the African ‘spinach’

Summary

Eggs of G. rhomboidalis are usually laid singly in separate excavations made with the snout of the beetle in either leaf petioles or tender portions of shoots of host plants, Amaranthus sp. At field temperatures fluctuating between 19°C and 30°C and in contact with water, eggs hatched in a mean of 2·8 days while unmoistened ones shrivelled up.

Beetle larvae bore and feed on the stele of host plants where development, up to adulthood, is completed in self-made larval galleries. On the average, the larvae are capable of consuming 40% and above of the cross-sectional areas of stems of infected host plants. In nature, multiple infection of host plants was quite common with 1–16 beetle larvae/plant rather usual. Consequently, the stem of virtually every healthy-looking host plant is internally traversed by larval galleries, at times even below ground level.

Adults bite their way out of the stem after a mean of 36·37 days from date of oviposition.

Larval damages to host plants are the gravest and bring about premature breakage and/or death of crops, stunted growth and reduced yield of the wanted leaf products.     

Morphology of Eogystia sibirica (Alphéraky) (Lepidoptera: Cossidae) attacking Asparagus officinalis in northern China with descriptions of its immature stages

The carpenter moth Eogystia sibirica (Alphéraky) (Lepidoptera: Cossidae) is a serious pest of the garden asparagus Asparagus officinalis (family Liliaceae) in northern China, with its larvae boring in the stem and roots, frequently causing significant damage to the plant. All the life stages of the pest, including egg, larva, pupa and adult, are described and illustrated in detail. The ovoid egg is covered with a reticulate meshwork of ridges on the chorion. The eruciform larva possesses only three stemmata on each side of the head; the reduced abdominal prolegs on segments III–VI each bear 35–55 uniordinal crochets arranged in two transverse bands; the short anal prolegs each bear five to seven uniordinal crochets in a transverse band. The pupa is adecticous and obtect, without cremaster. The reduction of larval stemmata and the invagination of the adult pterosterna are briefly discussed.     

Five invaginations and shedding of the larval epidermis during development of the hoplonemertean Pantinonemertes californiensis (Nemertea: Hoplonemertea)

We describe the planuliform larval development of the high intertidal hoplonemertean Pantinonemertes californiensis using confocal microscopy. We discovered that the newly hatched planuliform larva has two pairs of epidermal invaginations that disappear later in development. The anterior pair of invaginations has an apparent counterpart in other planuliform nemertean larvae; they give rise to the cerebral organs in at least two other hoplonemertean species. Although the adult P. californiensis possesses cerebral organs, we were not able to distinguish the anterior invaginations after 3 days of development. The developmental fate and homology of the posterior pair of invaginations is uncertain. We show that the proboscis develops in newly hatched larvae as a fifth distinct invagination just ventral of the apical plate. P. californiensis possesses a transitory larval epidermis, composed of approximately 80 multiciliated cells, which is normally shed at 3–4 days of development at 12–16°C.