Biological and ecological studies on the sugar-beet fly,Pegomyia mixta Vill. (Diptera: Anthomyiidae) on sugar-beet in Egypt

The sugar-beet fly, Pegomyia mixta Vill., is the most serious insect pest affecting sugar-beet plantations in Egypt. This study wase carried out in field in the El-Nubaria region ofEl-Behare Governorate. Peak numbers of flies were taken in sweep nets in December. Development of the fly appeared to be restricted to the months between November and May. In the hot months, adults were most active early in the morning and late in the afternoon, but in the cold months the peak of activity occurred at about midday. The flies were generally found on the upper surfaces of the leaves at temperatures below 16 °C and on the lower surfaces at temperatures above 24 °C. Females were generally more numerous than males. The eggs were observed from the first week of November to the end of April; the population was three blotches of eggs and 17 larvae/20 plants. The highest infestation of this insect in El-Nubaria was recorded at the end of March in both seasons (10 blotches of eggs, 20 larvae, and five pupae, and 12 blotches of eggs, 22 larvae, 13 pupae, respectively). The eggs are deposited in groups (3–8 eggs). The larvae bore its blotch in the leaf, about 3–7 larvae may be found in one blotch.     

Studies on an overwintering population of the mushroom phorid Megaselia halterata (Diptera: Phoridae) parasitized by Howardula husseyi (Nematoda: Allantonematidae)

An overwintering population of the mushroom phorid fly Megaselia halterata parasitized by Howardula husseyi was studied in an attempt to explain the winter decline in incidence of parasitism that has been observed in flies from mushroom farms. Fly larvae from eggs hatching in November developed into pupae in December and flies emerged in May. No selective mortality of parasitized specimens of larvae, pupae, or flies was observed. Dead parasites were found in only 10% of parasitized flies. The incidence of parasitism in the emerging flies (50%) was five times that of their parental generation and although parasitism significantly delayed fly emergence the delay was only 2–3 days. There was no evidence of winter decline in parasitism; instead there was strong evidence that parasitism enhanced phorid survival through the winter.     

Little effect of delayed mating on fecundity or fertility of female fungus gnats Lycoriella ingenua

The effect of delayed female mating for the mushroom fungus gnat Lycoriella ingenua is investigated. We examine the effect of delaying female mating on the fertility and egg viability of female flies that have a mating delay of 0–5 days after emergence. Male fly age is held constant. Female age does not impact male acceptance and most flies copulate within seconds of pairing. We find that female flies experiencing mating delays of 0–4 days after emergence lay a similar number of eggs onto artificial substrates. Females that experience a mating delay of 5 days lay 54% fewer eggs than those that mate on day 0 (day of emergence). There is no effect of mating delay on the percentage of larvae that emerge. The results of the present study indicate that mating delays have little effect on the fertility or fecundity of the mushroom fungus pest L. ingenua.     

Reproductive biology of the microtype tachinid fly Zenillia dolosa (Meigen) (Diptera: Tachinidae)

Reproductive biology including mating, adult longevity, fecundity and development of the tachinid fly Zenillia dolosa was investigated for optimizing rearing procedures using Mythimna separata as a host in the laboratory. Females lay microtype eggs containing a first instar larva on food plants of the host and then the eggs must be ingested by the host for parasitization. Mating success was 58.5% with mating duration of 80.7 min. Mating was most successful when day 0–1 females were kept with day 2–4 male flies. Female body size was positively correlated with its fecundity but not with longevity. However, females that survived longer produced more eggs during their lifetime. Parasitoids successfully developed in 4th to 6th instar host larvae. Host instars at the time of parasitoid egg ingestion significantly influenced development time of the immature parasitoid, but did not affect body size of the emerging parasitoid. We suggest that pairing newly emerged females with day 2–4 males should result in higher mating success and using the last instar hosts for parasitization should minimize development time of the parasitoid for rearing.     

Eat or be eaten: prevalence and impact of egg cannibalism on two-spot ladybirds, Adalia bipunctata

Ladybirds commonly engage in cannibalistic behaviour. Egg cannibalism by first instars is considered advantageous to the cannibal, because it not only results in direct metabolic gain but also a reduction in potential competitors. In this study, we quantified the effect of cannibalism on the development rate and survival of Adalia bipunctata (L.) (Coleoptera: Coccinellidae) larvae through development to the adult stage. We also assessed the synchrony of egg‐hatching in relation to laying order and compared the proportion of eggs cannibalized in egg batches laid as clusters or linearly. Larvae that had consumed a conspecific egg after hatching reached the adult stage 1.65 days earlier than those larvae that had not. Larval and pupal mortality was lower for cannibals compared to non‐cannibals; only 46% of non‐cannibalistic individuals reached the adult stage whereas 81% of cannibals pupated successfully. Egg cannibalism is undoubtedly advantageous to A. bipunctata larvae both in terms of faster development and increased survival. There is a positive correlation between laying and hatching order for eggs laid linearly or in a cluster. There was no significant difference in the proportion of eggs hatching in clusters or in a line (80 and 77%, respectively). The remaining eggs were either cannibalized or did not hatch. The ecological implications of these results are discussed with particular reference to trophic egg plasticity.     

Larval host plants of two lizard beetles in the genus Tetraphala (Coleoptera,Erotylidae, Languriinae,Languriini) from Taiwan,with a host plant list of Languriini

Lizard beetles (Erotylidae, Languriinae, Languriini) are known as stem borers of plants and contain agricultural pests and endangered species, but their species–host plant associations have been poorly documented. Here we investigated the larval host plants of two species of the genus Tetraphala Strum, T. collaris (Crotch) and Tetraphala sp. occurring in Taiwan. Females of T. collaris excavated living leafstalks and stems of the herbaceous dicot, Sambucus chinensis (Adoxaceae) using their mandibles for oviposition. We observed the eggs and early-instar larvae inside and nearby oviposition holes and late-instar larvae inside stems, suggesting that T. collaris uses living leafstalks and stems of S. chinensis as oviposition substrate and the larvae tunnel into stems with feeding on the tissues. Similarly, females of Tetraphala sp. excavated living leafstalks of the fern, Pteris wallichiana (Pteridaceae) using their mandibles for oviposition. We observed the eggs and early-instar larvae inside and nearby oviposition holes. When reared in laboratory, a larva reached adulthood inside the leafstalk. These results indicated that Tetraphala sp. uses living leafstalks of Pt. wallichiana as oviposition substrate and the larvae complete their development within. This study revealed that the genus Tetraphala contains both fern- and dicot-users during larval period. Further study is needed to clarify the evolutionary process of host plant use of languriines. Additionally, the host plant list of Languriini is provided.     

Taking a chance on moths: oviposition by Delia flavifrons (Diptera: Anthomyiidae) on the flowers of bladder campion, Silene vulgaris (Caryophyllaceae)

Abstract.

• 1 Delia flavifrons Zetterstedt (Diptera: Anthomyiidae) visits flowers of Silene vulgaris (Moench) Garcke (Caryophyllaceae), where the adults feed, mate, lay their eggs, and the larvae feed on developing seeds. The objective of the study was to examine how an ovipositing female fly assures a food resource for her progeny.
• 2 Ovipositing females preferred young, non-pollinated flowers over older pollinated ones. The flies did not pollinate the flowers and survival of the larvae depended on the flowers being pollinated by moths.
• 3 Flowers containing fly eggs were pollinated more often than expected from chance, probably as a result of both flies and moths visiting particular flowers.
• 4 Eggs were laid singly, and multiple oviposition occurred randomly. Although most eggs hatched, only about half produced larvae that made their way into the fruits. As a result, the probability of competition arising from multiple oviposition may be reduced to such an extent that selection does not favour females that avoid flowers with conspecific eggs.
• 5 Moth larvae of the noctuid genus Hadena also feed on the seed pods of S. vulgaris and will kill any fly larvae they encounter. However, there was no deviation from random oviposition by the flies in relation to eggs laid by the moths, but the competitively weaker fly usually started to lay eggs towards the end of the moth's egg-laying period.
• 6 The relationship between Delia flavifrons and Silene vulgaris superficially parallels that for known pollinator/predator systems, but floral adaptations to hypothetically pollinating flies seems not to have taken place.

     

Morphology and biology of Porphyrosela minuta Clarke 1953 (Lepidoptera: Gracillariidae, Lithocolletinae) in Uruguay

Porphyrosela minuta Clarke is a gracillariid that causes damage on white clover (Trifolium repens) in Uruguay. In this article, the eggs, all the larval instars, the pupa and the external morphological characteristics of the adult are described. Information about the insect's biology under laboratory and field conditions is presented. The eggs are laid singly on the upper surface of the leaflets. The larvae make extensive mines that appear as white blotches. The larvae develop through five instars and do not remain exposed during their development. At 25 degrees C the life cycle lasted 16.2 days, made up of 3.0 for eggs, 8.8 for larvae and 4.4 for pupae. Females began laying on the first night, and during an oviposition period that varied between five and 12 days deposited an average of 71.8 eggs. It is a multivoltine species and seven to nine generations occur between November and the end of March.     

A case of abnormal size in eggs and larvae of the Taiga tick,Ixodes persulcatus (Acari: Ixodidae)

Egg batches laid by females of Ixodes persulcatus (maintained under a photoperiod of L:D 20:4 before feeding) contained eggs of two sizes: numerous normal eggs of 0.578 × 0.421 mm and some giant eggs of 0.776×0.515 mm. Giant eggs were 32–34% greater in length and 22–24% greater in width than normal eggs. Females maintained under a short-day photoperiod (L:D 12:12) laid only normal eggs (0.588×0.417 mm). There were no differences between these eggs in viability and developmental time, but larvae hatched from giant eggs were larger (length of body 23–28% greater and of gnathosoma 12–15% greater) than larvae from normal eggs. This dimorphism of eggs and larvae was not sex determined, but may be a maternal photoperiodic effect.     

Use of water hyacinths as shelter,foraging place,and transport by young piranhas,Serrasalmus spilopleura

Synopsis The water hyacinth, Eichhornia crassipes, plays an important role in the early life of the piranha, Serrasalmus spilopleura in southeastern Brazil. Larvae and early juveniles are found by both day and night among the roots of this free floating waterweed, thus gaining shelter, a rich foraging place, and potential rafting dispersal. Piranha larvae up to 19 mm SL feed mainly on small aquatic arthropods, slowly searched for inside the root tangle; larger juveniles tend to leave the plants and patrol more open areas. At 24 mm SL young piranhas begin to clip out pieces from fins of other fishes and seek shelter in water hyacinths only at night. About 30% of the rafting clumps of water hyacinths may harbour one to three piranha larvae, providing dispersal during floods.     

Laboratory biology and impact of a stem-boring weevil Apocnemidophorus pipitzi (Coleoptera: Curculionidae) on Schinus terebinthifolia

Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae), was introduced into Florida, USA, from South America as an ornamental plant in the late 19th and early 20th centuries. It eventually escaped cultivation and is a serious threat to the state’s biodiversity. In the 1980s, this invasive weed was targeted for classical biocontrol. Surveys for natural enemies of Brazilian peppertree conducted in the native range resulted in the discovery of several candidate biocontrol agents. A stem-boring weevil identified as Apocnemidophorus pipitzi (Faust) was collected in Paraguay and transported under permit to Florida, USA. A laboratory colony of A. pipitzi was established in April 2007 by caging adults on cut branches of Brazilian peppertree supplemented with leaf bouquets. Adults are defoliators that feed mainly on the upper surface of subterminal leaflets. Females deposit eggs singly inside the stems and larvae feed under the bark where they damage the vascular cambium. There are five instars, pupation occurs inside the stem and a new generation is produced in 3–4 months. Growth of potted plants with and without exposure to weevil herbivory was compared over an 11-month period. Feeding damage by adults and larvae significantly increased leaf abscission and reduced leaf and root biomass accumulation.     

X-ray doses to safely release the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) reared on Anastrepha fraterculus larvae (Diptera: Tephritidae)

Diachasmimorpha longicaudata is a koinobiont larval parasitoid that is currently used to control fruit flies of the genera Anastrepha, Ceratitis and Bactrocera. In the rearing process, a fraction of the host larvae that are exposed to parasitoids escape from parasitism and develop into viable and fertile flies. This creates the need to eliminate emerging flies before the parasitoids are shipped for release, increasing costs due to additional handling steps. Exposure of fly eggs or larvae to gamma-irradiation before they are parasitised has been used to reproductively sterilise hosts, or even inhibit their emergence. Our aim was to determine whether X-ray radiation applied to Anastrepha fraterculus third instar larvae before they are exposed to parasitoids, inhibits fly emergence in non-parasitised larvae without affecting the performance of the parasitoids that emerge from parasitised larvae. Three X-ray doses: 6250.2 R, 8333.6 R and 10417 R (equivalent to 60, 80 and 100 Gy, respectively) and one γ-ray dose (100 Gy) were tested. Fly emergence decreased with increasing doses of radiation, showing null values for the higher X-ray dose and the dose of 100 Gy. Irradiation showed either no impact or a positive effect on parasitism rate and fecundity. Sex rate was biased towards females in almost every dose. We conclude that the two types of radiation evaluated here were equally effective in suppressing fly emergence with no detrimental effects on the biological quality of the produced parasitoids. X-rays offer an alternative method of irradiation than the conventional radiation source, i.e. γ-rays. These results represent a significant improvement in the development of a biological control programme against A. fraterculus.     

Maternal care in the red-headed spruce web-spinning sawfly,Cephalcia isshikii (Hymenoptera: Pamphiliidae)

We describe oviposition and maternal behavior in the sawfly Cephalcia isshikiiand examine the adaptive significance of this behavior. Females deposited eggs in a single but loose cluster on needles of terminal twigs of spruces, Piceaspp., and remained with the eggs usually on the underside of the twig facing toward the tip. The female attended her eggs until death without taking food but did not follow the first-instar larvae that moved from natal needles even if she survived until then. When the female was disturbed, she usually moved toward the source and attempted to bite it. Though at much lower frequencies, this aggressive behavior was also observed in gravid females and even in males. Field observations and female removal experiments indicated that the female enhanced the survival of the eggs through the reduction of arthropod prédation.     

Egg and larval load assessment and its influence on oviposition behaviour of the leaf beetle Galerucella nymphaeae

The oviposition behaviour of the water-lily beetle Galerucella nymphaeae was examined. This species is a specialist herbivore on the floating leaves of nymphaeids Nymphaeaceae and especially on the yellow water-lily, Nuphar lutea. Females lay their eggs in clutches on the leaves, and after hatching, the larvae feed on the leaves. The quality of the leaves decreases quickly after the larvae hatch, and eventually the leaves will sink below the water surface, whereupon the eggs, 1st-instar larvae and pupae are killed by drowning. The influence of conspecific eggs, larvae and feeding tracks on the oviposition preferences of the beetles was tested. Females were allowed to choose between fresh leaves and leaves with conspecific eggs and larvae as well as between leaves with larvae and leaves with feeding tracks but no larvae. An attempt was also made to determine whether eggs and larvae affect the oviposition rate of females when they are not given the opportunity to oviposit on untouched leaves. The results indicate that females tended to avoid leaves with conspecific larvae or to exhibit a decreased oviposition rate on such leaves. Females also avoided conspecific eggs, although the oviposition rate was not influenced by the presence of conspecific eggs. When females were allowed to choose between leaves with larvae and leaves with feeding tracks, possible discrimination against leaves with larvae just fails to reach the 5% level.     

Effects of gamma irradiation on the life stages of yellow flower thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae)

Irradiation at a minimum absorbed dose of 250 Grays (Gy) has been approved by the USDA as a quarantine treatment for certain fruits in Hawaii to control four species of tephritid fruit flies. Subsequent research must determine whether this dose is sufficient to control other quarantine pests, such as mealybugs, thrips, mites, beetles, moths, and scale insects, on other commodities with export potential that are approved for irradiation treatment for fruit flies. This study demonstrated that irradiation at 250 Gy caused non‐emergence of eggs and pupae, failure of larval development, and sterility of adults of yellow flower thrips, Frankliniella schultzei (Trybom). Adults were the most resistant stage tested, with 100% mortality at 57, 36 and 30 days post‐treatment for the 250, 350 and 400 Gy treatments, respectively. Untreated adults survived up to 66 days. After receiving an irradiation dose of 250 Gy, no one‐ to two‐day old eggs hatched successfully, while 3–4‐day old eggs hatched but did not develop beyond the larval stage. Of the controls, 96.0% of 1–2‐day old eggs and 75.9% of the 3–4‐day old eggs hatched and survived through pupation. No first or second instar larvae treated with a target dose of 250 Gy were able to pupate. When pupae were irradiated at 250 Gy, 37% emerged as adults and all were sterile compared to 88.3% emergence of controls.     

Erythritol ingestion impairs adult reproduction and causes larval mortality in Drosophila melanogaster fruit flies (Diptera: Drosophilidae)

Previous feeding studies showed the polyalcohol erythritol was toxic when ingested by adult laboratory fruit flies (Drosophila melanogaster). We asked whether erythritol could additionally affect fly population growth either through larval toxicity or through effects on adult reproduction. Females did not avoid laying on food substrates with 1M erythritol; laying rate on 1M erythritol food was similar to control food when females were given free‐choice access. Eggs laid or placed on 0.5 M to 2.5 M erythritol foods hatched at normal rates, suggesting erythritol was not toxic to eggs upon contact. Drosophila melanogaster larvae readily consumed food containing 1 M erythritol, but none of these larvae reached pupation. Longevity of larvae feeding on in 1 M erythritol food was significantly reduced relative to controls, and mean ± SE larval lifespan on erythritol was 1.54 ± 0.10 days (max. = 3 days). Exposing cohorts of second‐instar larvae to food with varying concentrations of erythritol showed the LD50 (at 24 hr) concentration was approximately 0.6 M. Taken together, these results suggest erythritol could be employed in effective larval‐sink baits. Adults flies fed with erythritol produced significantly fewer eggs on days when they fed on 1 M erythritol, and egg production was significantly reduced for one additional day after the adults were moved to control food. These findings suggest erythritol is rapid and effective at temporarily suppressing D. melanogaster reproduction, increasing its potential for use in effective insect population control.     

Biology of Anagrus atomus (Hymenoptera: Mymaridae), an egg parasitoid of the grape leafhopper Arboridia kermanshah (Homoptera: Cicadellidae)

Biology, morphology and oviposition behavior of Anagrus atomus (Linnaeus), an egg parasitoid of the grape leafhopper Arboridia kermanshah Dlabola in Isfahan, Iran, were investigated. Adults were smaller than those so far reported from other regions. Females continuously drummed on plant surfaces with their antennae to search for host eggs. Parasitoid eggs hatched 2–3 days after oviposition, and A. atomus had two larval instars. First instar larvae were sacciform and immobile. Second instar larvae appeared 4 days after oviposition and were very active, and doubled their body length. The prepupal and pupal stages lasted for 1 and 5–6 days, respectively. Adult emergence began 16 days after oviposition, and peaked on day 17.     

Differential Kin Discrimination by Red-spotted Newts (Notophthalmus viridescens) and Smooth Newts (Triturus vulgaris)

In organisms lacking parental care or when eggs of more than one female are layed together, parents preferentially tend to avoid eating their own offspring. In some species of newts (Caudata: Salamandridae), there is no parental care and cannibalism of eggs and larvae occurs when philopatric adults remain in the pond throughout the breeding season where eggs and larvae develop. Kin discrimination by both adult newts and larvae would be expected to occur during the breeding season as it would enable individuals to benefit from the nutrients obtained from eating eggs and larvae while they avoid eating close relatives. The effects of kinship on cannibalism of eggs and larvae were examined in two species of newts. In separate, but similar, paired behavioral trials adult female red-spotted newts, Notophthalmus viridescens, and smooth newts, Triturus vulgaris, were allowed to consume their own egg or an egg from another female. Female red-spotted newts, but not smooth newts, preferred to eat eggs of other females rather than their own, and overall smooth newts were ‘reluctant’ to eat conspecific eggs. To test for ontogenetic shifts in discrimination abilities, additional experiments were performed with adult female red-spotted newts paired with their own larvae and a larva from another female. In addition, the effects of kinship on the attraction or repulsion of larvae was also studied in red-spotted newts. Females showed no significant discrimination abilities during acts of cannibalism on larvae. Larvae spent similar amounts of time with siblings and non-siblings. These results suggest that the ability of adult newts to discriminate among eggs varies between species and that the elicitation of a kin-discrimination response may be context-dependent. For red-spotted newts, there was no evidence of discrimination abilities within and between other life-history stages.     

Parasitism of Heterotylenchus autumnalis Nickle (Nematoda: Sphaerulariidae) to the Face Fly,Musca autumnalis De Geer (Diptera: Muscidae)

New information is reported on the parasitism of Heterotylenchus autumnalis upon its principal known host, Musca autumnalis. Black to brown spots are produced on the cuticle of all infected host larvae where the nematode penetrated. The principal damage to the host is castration of the female. In laboratory tests nematode larvae were not infective and did not leave the hosts before the female fly was 1 1 days old. Nematode larvae removed from infected male flies infected other hosts, but it is believed that in nature these larvae are unable to leave the host.     

The effects of temperature on development of the large narcissus fly (Merodon equestris)

Eggs, larvae, pupae and adults of the large narcissus fly (Merodon equestris) were reared at a series of constant temperatures between 9–24°C. Egg development required from 37 days at 9°C to 7 days at 21.5°C. The low-temperature threshold for development was 6.7°C. Larvae reared at 1424°C were fully-grown after 18 weeks, but it took much longer for such insects to pupate, and adult flies emerged only after about 45 weeks of development. Large narcissus flies enter diapause during the larval stage and overwinter as fully-fed larvae, forming pupae in the following spring. Post-winter pupation and pupal development took from 169 days at 10°C to 36 days at 21.5°C. Of this, pupal development required from 91 days at 10°C to 19 days at 21.5°C. The low-temperature threshold for post-winter pupation and pupal development was 7.1°C, and for pupal development alone, 7.2°C. Females maintained at or below 19°C laid few eggs, whereas some females kept at or above 21.5°C laid more than 100 eggs (mean 69 ± 36). Approximately 50% of females maintained at or above 21.5°C laid less than 10 eggs during their lifetime. The mean egg-laying time was 6 to 9 days. Although temperatures at or below 19°C inhibited mating, once a female had mated, such temperatures did not prevent oviposition.