Mortality factors and resource use of the bud-galling sawfly, Euura mucronata (Hartig), on willows (Salix spp.) in arctic Eurasia

We studied egg and larval mortality factors in arctic populations of the bud-galling sawfly, Euura mucronata (Hartig) on three willow species (Salix glauca L., S. phylicifolia L., and S. lapponum L.) and the quality of resources (shoot length of willows) required for egg-laying. The survival was independent of latitude. There was a positive correlation in survival on different willow species among sampling sites, indicating that similar, locally operating factors affected survival. Host plant-based mortality factors were dominant and caused 17.9–48.0% mortality in eggs and 6.6–44.1% mortality in larvae. Parasitoids and inquilines caused relatively low and variable rates of mortality. Parasitoids were absent from several of the northernmost populations, but caused up to 11.0% mortality at southern sites. Mortality caused by inquilines was minor in other areas except in some sites in the Taymyr Peninsula, where it varied from 0 to 23.1%. E. mucronata laid eggs on the longest shoots available. Plant vigour as measured by shoot length decreased toward the north, and densities of galls were positively correlated with plant vigour. The difference in length between galled and ungalled shoots was 2.0- to 4.6-fold. Absence of E. mucronata in the most northern populations of willows was apparently caused by insufficient shoot growth. Short shoots failed to provide sufficient resources for successful development of galls. Our results suggest that the quality of host plants is the main factor determining abundance and distribution of E. mucronata in arctic areas. Received: 10 February 1997 / Accepted: 2 May 1997     

Plant age and attack by the bud galler,Euura mucronata

Summary As ramets of the willow, Salix cinerea L. (Salicaceae) aged shoot length decreased in the six populations studied in S.E. Finland. Many traits correlated positively with shoot length: basal diameter, number of internodes, internode length, leaf size, and length of growing period. The bud-galling sawfly, Euura mucronata (Hartig) Man. (Churchill) (Hymenoptera: Tenthredinidae), responded positively to shoot length or correlated traits, and negatively to ramet age in three forest populations. This herbivore attacked the most vigorous plants in a population, and numbers of attacks declined as ramets aged and senesced. The generality of this kind of herbivore response to plant quality is emphasized.     

Oviposition and mining by Phytobia betulae (Diptera: Agromyzidae) in genotypes of European white birch (Betula pendula)

Abstract 1 The colonization success of herbivorous insects depends partly on the ability of females to choose suitable host plants. Phytobia betulae Kangas (Diptera: Agromyzidae), a miner of differentiating xylem, infests birch (Betula pendula Roth and Betula pubescens Ehrh.) trees. 2 In a field experiment we measured successful ovipositions in the long shoots of eight 5‐year‐old‐birch genotypes. Later in the growing season, in the same experiment, we counted the number of larvae from the same birch genotypes (different replicates). 3 We attempted to determine where Phytobia females lay their eggs in the birch canopy, what kind of shoots Phytobia utilize, whether birch genotypes differ in their susceptibility to Phytobia, and which tree characteristics correlate with successful utilization of birch for oviposition and larval development. 4 The ovipositions were concentrated in fast growing shoots and only 5% of the available shoots were utilized. Usually a shoot contained only one oviposition (80% of the cases). However, oviposition pattern resulted in significant aggregations (two to four ovipositions per shoot): 11% of shoots selected for oviposition contained more than one Phytobia and 22% of larvae shared their shoot with at least one other larva. Although birch shoots were much more abundant than Phytobia, there may be intraspecific competition for host resources among Phytobia. 5 Birch genotypes differed in the number of ovipositions but not in the number of larvae, although in general the number of larvae was correlated positively with the number of ovipositions. There were more ovipositions in the faster growing genotypes.     

The effect of abiotic factors on foraging and oviposition success of the aphid parasitoid,Aphidius rosae

Searching patterns and oviposition success of the aphid parasitoid Aphidius rosae were analysed in different abiotic conditions (simulated wind, simulated drizzling rain, simulated shower, high temperature, low humidity, standard conditions) in the laboratory. Residence times, time allocation and oviposition success did not differ significantly between females foraging on rose shoots during periods with high temperature (>33°C) and low humidity (35%–40% relative humidity) and females searching under standard laboratory conditions (20°C, 65%–70% relative humidity, no wind). A wind speed of 2 m/s reduced the oviposition numbers significantly, and females spent much more time resting than searching for hosts. Females did not leave a shoot during wind, but departed quickly after wind had ceased. Simulated drizzling rain or simulated showers had the strongest effects on A. rosae foraging. Both types of rain prevented all foraging activities including departure from the shoot, and females laid no eggs during rain. After rain had stopped, females were mainly engaged with cleaning themselves and laid relatively few eggs compared to standard conditions. The impact of unfavourable abiotic environmental factors like wind or rain may help to explain why many parasitoids lay only a small proportion of their available eggs when foraging in the field.     

Why does the bud-galling sawfly,Euura mucronata,attack long shoots?

Summary The bud-galling sawfly, Euura mucronata, attacked longer shoot length classes on its host, Salix cinerea, more frequently than shorter shoots. Shoot length accounted for 76 to 93 percent of the variance in number of galls per 100 shoots in three habitats: forest, watermeadow, and lakeside. The reasons for this pattern were addressed with studies on shoot length in relation to: 1. Number of resources (buds) per shoot; 2. Success in establishment of larvae in galls; 3. Gall size and resources per gall; and 4. Survival of larvae after establishment as influenced by plant resistance and natural enemy attack. The most important factors proved to be success in establishment of larvae, with percent of variance accounted for ranging from 57 to 77 percent in three of four sites where relationships were significant, and survival after establishment of larvae, with variance accounted for ranging from 40 to 54 percent in the same three sites. The pattern of survival was dictated by plant resistance and not by natural enemies. These two additive factors resulted in a general relationship across all sites of increasing emergence of fully developed larvae per cohort as shoot length increased, accounting for 78 percent of the variance. These adaptive advantages to attacking longer shoots are sufficient to account for the pattern of increased probability of shoots being attacked as they increase in length.     

Resistance and susceptibility of Boronia megastigma cultivars to infestations by the psyllid Ctenarytaina thysanura

Studies were conducted on 23 boronia cultivars to determine the mechanisms of resistance and susceptibility to the psyllid, Ctenarytaina thysanura Ferris and Klyver. No antibiosis effects were detected in any of the boronia cultivars investigated. No cultivar was tolerant to C. thysanura attack. However, in both free-choice and no-choice tests in the glasshouse, ovipositional antixenosis (non-preference) was detected in cultivar HC27, whereas cultivars HC4 and HC142 were most preferred for oviposition. Measurement of terminal shoot hardness of cultivars revealed variations in relative hardness. Given a choice between boronia cultivars of the same size and colour but of differing hardness of the terminal shoots, C. thysanura laid more eggs on those cultivars with softer terminal shoots (HC4 and HC142) and laid fewest eggs on harder terminal shoots (HC27). This may explain differences in the psyllid population on different cultivars in the field. Fewer eggs were laid on terminal shoots exceeding a hardness rating of 80 g/mm terminal shoot thickness.     

Effects of time-dependent intraspecific competition on offspring survival in the butterfly, Anthocharis scolymus (L.) (Lepidoptera: Pieridae)

Effects of mothers' eclosion and oviposition timing on the survival of their offspring in the pierid butterfly Anthocharis scolymus (L.) was examined. I recorded the performance of individual eggs and larvae that differed in their mother's eclosion and oviposition timing in a natural population, where A. scolymus feeds on Turritis glabra (L.) Bernh. Eggs laid early in the season, and larvae emerging from these eggs, had higher survival than eggs laid later, and larvae emerging from eggs that were laid later in the season, the causal factor being egg cannibalism by larvae on the same host plant. Logistic regression showed that females eclosing early in the season had higher offspring survival than females eclosing later. I conclude that optimal timing of adult eclosion in A. scolymus is a trade-off between eclosing early with associated higher offspring survival but lower egg-laying rate, and eclosing later with associated lower offspring survival but higher egg-laying rate. Received: 4 August 1997 / Accepted: 19 October 1997     

Growth of coyote willow and the attack and survival of a mid-rib galling sawfly,Euura sp.

We studied the relationship between variation in age and shoot characteristics of the host plant Salix exigua Nuttall (coyote or sandbar willow) and the attack and survival of Euura sp. (an unnamed leaf-midrib galling sawfly). Variation in shoot characteristics resulted from reduced growth as willow ramets aged. Mean shoot length per ramet and mean longest leaf length per shoot decreased by 95% and 50% respectively between 1- and 9-year-old willow ramets. All measured shoot characteristics-shoot length, longest leaf length, number of leaves per shoot, and mean internode length-were significantly negatively correlated with ramet age (r ² ranged from –0.23 to –0.41). Correlations between shoot characteristics were highly positive, indicating that plants also grew in a strongly integrated fashion (r ² ranged from 0.54 to 0.85). Four hypotheses were examined to explain sawfly attack patterns. The host-plant hypothesis was supported in explaining enhanced larval sawfly survival through reduced plant resistance. As willow ramets aged, the probability of Euura sp. attack decreased over 10-fold, from 0.315 on 1-year-old ramets to 0.024 on 2- to 9-year-old ramets. As shoot length increased, the probability of sawfly attack increased over 100-fold, from 0.007 on shoots <100 mm, to 0.800 on shoots in the 1001–1100 mm shoot length class. These attack patterns occurred even though 1-year-old ramets and shoots >500 mm each represented less than 2% of the total shoots available for oviposition. Host plant induced mortality of the egg/early instar stage decreased by 50% on longer leaves and was the most important factor determining survival differences between vigorous and non-vigorous hosts. Sawfly attack was not determined by the resource distribution hypothesis. Although shoots <200 mm contained 82% of the total leaves available, they contained only 43% of the galls initiated. The attack pattern also was not explained by the gall volume hypothesis. Although gall volume increased on longer shoots, there was no significant variation in mid or late instar mortality over shoot length, as would be expected if food resources within smaller galls were limited. The natural enemy attack hypothesis could not explain the pattern of oviposition since predation was greater on longer shoots and leaves. In addition, larval survival was related to oviposition behavior. Due to a 69% reduction in late instar death and an 83% reduction in parasitism, survival of progeny in galls initiated close to the petiole base was 2.8 times greater than in galls initiated near the leaf tip. A 75% reduction in gall volume over this range of gall positions may account for the observed increases in late instar mortality and parasitism.     

Semiochemical mediation of oviposition by the phlebotomine sandfly Lutzomyia longipalpis

Abstract. Extracts of rabbit food, hay and rabbit faeces elicited a positive oviposition response from gravid female Lutzomyia longipalpis sandflies (Diptera: Phlebotominae). Combined extract of rabbit food and oviposition pheromone had a synergistic effect on sandfly egg-laying, greatly increasing the number of eggs laid and resulting in a highly targeted response. Individually tubed flies, exposed to the combined extract, were shown to be 3.5 times more likely to survive oviposition and laid 2.5 times more eggs than control flies. A laboratory oviposition trap baited with the combined extract was tested in a cage and caught 31 (62%) of 50 gravid L.longipalpis over a 72h period.     

Searching at different spatial scales: the foraging behaviour of the aphid parasitoid Aphidius rosae in rose bushes

The searching patterns of the aphid parasitoid Aphidius rosae were analysed at three different spatial scales: leaves, shoots and bushes. Parasitoid females searched aphid-infested leaves and shoots intensively and remained on average more than twice as long on infested than on uninfested shoots. Patch times and oviposition numbers per shoot were highly variable both between females and for different shoot visits within females. However, at the shoot and bush level low oviposition numbers were generally found. The time spent on different behavioural patterns (searching, resting, feeding, host handling) changed significantly during subsequent shoot visits of individual females but oviposition success was not influenced by this change. Parasitoids searched individual leaves and shoots mainly by walking, while moving between shoots occurred exclusively by flight. The travel time between shoots (i.e. flight time) accounted for less than 1% of the residence time in a bush. At the bush level foraging was characterized by a high ability to localize infested shoots and consequently little time was wasted in searching on uninfested shoots. The pattern of resource exploitation of individual females was consistent with the distribution of A. rosae larvae in field samples taken from individual rose bushes.     

Dynamics of growth,carbon and nutrient translocation in Zizania latifolia

We studied the seasonal resource dynamics between organs of wild rice (Zizania latifolia (Griseb.) Turcz. ex Stapf.) to obtain a better understanding of its growth dynamics, carbon and nutrient translocation. The results of observation from January 2002 to February 2004 showed the shoot density markedly increased after emergence of shoots at the end of March until May (up to 800 ind/m²). However the shoot mortality due to self-thinning reduced the total new shoots by more than 70% by the end of July. Thereafter, the shoot density was nearly constant with the aboveground biomass peaking at the end of August. In the late winter, the rhizome biomass declined by respiration loss to about 25% of its peak value. Meanwhile the decline in rhizome reserves from January to the end of April was about 20%. This small reduction compared with other perennial emergent species implies that there is a lower contribution of rhizome reserves to support new shoot formation. The initial heterotrophic growth of new shoots based on the rhizome resources lasted for a short period, then switched to autotrophic growth at the end of April or the beginning of May. Thus, in most periods of foliage development, nutrients were obtained mostly from soil through uptake by roots, not through resource allocation of the rhizome. In autumn, the standing dead shoots retained most of the nutrients and carbohydrates without translocating downwards. This suggests that in practice, the plant can remove nutrients from sediment more efficiently than other emergent plants.     

Field oviposition rates and egg load dynamics of pollen beetles (Meligethes aeneus Fab.) (Colepotera: Nitidulidae)

Abstract 1 Egg loads from field collected pollen beetles (Meligethes aeneus Fab., Coleoptera: Nitidulidae) were determined by dissecting beetles caught at the beginning and end of the putative daily oviposition period. Field collected beetles were offered Brassica napus (L.) plants in cages for 8 (morning and early afternoon), 16 (overnight), and 24 h to ascertain the number of eggs laid during these time periods. 2 Most eggs were laid in the morning and early afternoon. The proportion of gravid females was higher at the beginning of the oviposition period than at the end. Most females in the morning carried two eggs, whereas one egg was more common in the afternoon. 3 We hypothesized that the number of eggs laid during the oviposition period would be equivalent to the difference between egg loads at the beginning and end of oviposition. This was not the case; differences in egg loads were significantly lower than number of eggs laid. However, the number of eggs laid was equivalent to the egg load at the beginning of the oviposition period, suggesting that eggs available in the morning are laid during the following day. 4 Population estimates of daily oviposition rates, approximately 0.7 eggs per beetle and day, were close to estimates from laboratory studies when the proportion of gravid females was taken into consideration.     

The pollen beetle, Meligethes aeneus, changes egg production rate to match host quality

Motivation-based models dominate current theory concerning host plant selection for oviposition by herbivorous insects. A female searching for a host plant will be more likely to accept a host which is of inferior quality for her offspring if motivation is high, e.g. a large eggload or long time since last oviposition. This implies that insects will accumulate eggs if exposed to hosts of low acceptability and after a time lay eggs on such hosts. An alternative strategy for insects when exposed to less acceptable hosts is to stop producing, instead of accumulating, eggs. Thus, resources would be saved until a more acceptable host is found. If this hypothesis is true, a herbivorous insect would cease egg production when exposed to hosts of low acceptability and resume egg production when exposed to hosts of high acceptability. Previous exposure should not affect oviposition rate when an insect encounters a new host of a different quality. In an earlier study pollen beetles, Meligethes aeneus (F.) (Coleoptera: Nitidulidae), did not accumulate eggs in the absence of high quality hosts. In this study we monitored the daily oviposition rate of female pollen beetles on hosts plants of low (Sinapis alba L.), intermediate (Brassica nigra Koch) or high (B. napus L.) acceptability over a 5-day period. Individuals were then switched to an oviposition resource of a different acceptability. Beetles moved from high- to low-acceptability plants reduced their oviposition rate considerably. In the opposite case, low to high acceptability, the rate of oviposition increased markedly after the switch. When M. aeneus were moved from the high-acceptability host to that of intermediate acceptability oviposition rate was modified accordingly. However, when moved to the intermediate host from a host of low acceptability oviposition on B. nigra was much less than would normally be expected. A possible mechanism for this finding is discussed. M. aeneus, by adjusting oviposition rate to host acceptability, maximizes the average host quality for offspring, even at the cost of a lower egg-laying rate. Received: 5 October 1998 / Accepted: 20 April 1999     

Oviposition preference and larval performance of Epiphyas postvittana (Lepidoptera: Tortricidae) on Botrytis cinerea (Helotiales: Sclerotiniaceae) infected berries of Vitis vinifera (Vitales: Vitaceae)

In this paper we tested the behavior of gravid Epiphyas postvittana in selecting the most‐appropriate site for oviposition thus benefitting offspring performance. Our hypothesis was built on Jaenike's preference–performance hypothesis (also referred to as the “mother‐knows‐the‐best” hypothesis). To test this, we used the interacting Epiphyas postvittana, its host Vitis vinifera, and the pathogenic microbe Botrytis cinerea system. Populations of E. postvittana and B. cinerea often exist concurrently on V. vinifera in Australasia and their interaction and mutual influence are currently being explored, although the suggestion presently is that the relationship between E. postvittana and B. cinerea is mutualistic. We tested the effect of volatiles from B. cinerea‐infected berries and uninfected (control) berries of V. vinifera on the oviposition behavior of E. postvittana. We also characterized the effects of B. cinerea infection on the berries of V. vinifera on the growth and development of E. postvittana. Contrary to the preference–performance hypothesis, oviposition choices made by gravid E. postvittana did not result in the best offspring survival, development, and performance. The preference for oviposition by E. postvittana was strongly influenced by the olfactory and tactile cues. She laid fewer eggs on B. cinerea‐infected berries compared to uninfected berries of V. vinifera. The larvae of E. postvittana showed no preference to uninfected berries of V. vinifera. The larvae fed on B. cinerea‐infected berries of V. vinifera showing greater survival rate, shorter time to pupation, greater pupal mass, and on becoming adults they laid more numbers of eggs than the larvae that were enabled to feed on uninfected berries. The larvae of E. postvittana transport the conidia of B. cinerea and transmit grey‐mould disease to uninfected berries of V. vinifera.     

Long term oviposition preference and larval performance of Schizomyia macrocapillata (Diptera: Cecidomyiidae) on larger shoots of its host plant Bauhinia brevipes (Fabaceae)

The Plant Vigor Hypothesis (PVH) proposes that natural selection on female oviposition choice results from higher fitness of larvae on more vigorous and larger plant modules. For six consecutive years we tested the PVH predictions by investigating the effect of shoot size of Bauhinia brevipes (Fabaceae) on the oviposition preference and offspring survival of the gall-midge Schizomyia macrocapillata (Diptera: Cecidomyiidae). Additionally, we analyzed the effects of bottom-up and top-down mortality forces on the system. The hypersensitive reaction (bottom-up effect) accounted for more than 90% larval mortality of S. macrocapillata, making available few galls to be found and killed by natural enemies (top-down effect). Smaller shoots were always more abundant while longer shoots were rare. Nevertheless, the percent number of galls induced by S. macrocapillata was up to 10-fold greater on the largest shoots, corroborating the preference prediction of the PVH. Schizomyia macrocapillata should use over-exploit larger shoots to maximize the preference for, and consequently increase the performance on these shoots. Our results partially support the performance prediction of the PVH: (1) the observed survival was higher than expected on longer shoots, and (2) the ratio of survival per shoot was positively related with shoot length only in 2 years. Thus, we found a link between female preference and larval performance on large-sized shoots, at least in some years. The gall-midge attack pattern in this study might be an evolved response to maximize the female preference and increased larval performance on longer shoots of the host plant.     

Indirect effects mediated by compensatory shoot growth on subsequent generations of a willow spittlebug

 We investigated whether oviposition by the spittlebug Aphrophora pectoralis on Salix miyabeana and S. sachalinensis in fall 1998 affected shoot growth pattern and further oviposition by subsequent generations of the willow spittlebug in early September 1999 and 2000. Spittlebug oviposition enhanced the growth of current-year shoots on 1-year shoots with oviposition (O-shoots) compared to those without oviposition (N-shoots): the length of current-year shoots increased in 1999 and 2000, the number of current-year shoots increased in 2000 despite a decrease in 1999, and the shoot abscission rate decreased during the 1999 winter. The number of egg masses per current-year shoot was greater on O-shoots than on N-shoots in 1999, and this tendency was reinforced in 2000. The total number of egg masses was greater on O-shoots than on N-shoots in 2000, although there was no significant difference in 1999. There is thus a positive feedback system between spittlebug attack and compensatory growth on willow. Received: April 11, 2002 / Accepted: July 30, 2002 Present address: Center for Ecological Research, Kyoto University, Otsu, Japan Acknowledgments We thank Masanori J. Toda and Andrew Davis for valuable comments and critical reading on this paper. Financial support was provided by a Japanese Ministry of Education, Science, Sports, and Culture Grant-in-Aid for Creative Basic Research to Takayuki Ohgushi. Correspondence to:A. Nozawa     

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.

     

Within‐plant variation in defences in response to simulated herbivory in a semi‐arid southern African savannah

Within‐plant spatial variation in herbivore pressure can induce localized antiherbivory defence responses. We tested this hypothesis by studying branch‐specific responses of Acacia robusta, Dichrostachys cinerea and Ziziphus mucronata to simulated mammalian herbivory. Herbivory was simulated by clipping the terminal shoots (3 cm from tip) of tree branchlets, allowing them one year of regrowth and then comparing their spine length and density and condensed tannins with those of adjacent unclipped branchlets. Condensed tannins concentrations were higher in clipped branchlets than in unclipped branchlets in all three woody species (P < 0.05). Spine length was higher in clipped branchlets than in unclipped branchlets in A. robusta (P < 0.05) but was similar in both D. cinerea and Z. mucronata (P > 0.05). Spine density was double in clipped branchlets as compared to the unclipped branchlets in Z. mucronata (P < 0.05) but was similar in both A. robusta and D. cinerea (P > 0.05). We found evidence of within‐plant variation in condensed tannins concentration and spine length and density in response to simulated herbivory in the three woody species.     

Organogenesis, shoot regeneration, and flowering response of Vernonia cinerea to different auxin/cytokinin combinations

Summary A viable protocol has been developed for direct and indirect shoot regeneration of Vernonia cinerea. To establish a stable and high-frequency plant regeneration system, leaf and stem explants were tested with different combinations of α-naphthalene acetic acid (NAA), indole-3-acetic acid (IAA), and benzylaminopurine (BA). Lateral buds on nodal explants grew into shoots within 2 wk of culture in Murashige and Skoog (MS) basal medium supplemented with 20.9 μM BA. Excision and culture of nodal segments from in vitro-raised shoots on fresh medium with the same concentration of BA facilitated development of more than 15 shoots per node. Similarly leaf, nodal, and internodal explants were cultured on MS basal medium supplemented with different concentrations of BA, NAA, and IAA either alone or in combinations for callus induction and organogenesis. Shoot buds and/or roots were regenerated on callus. Shoot buds formed multiple shoots within 4 wk after incubation in induction medium. Adventitious buds and shoots proliferated when callus was cut into pieces and subcultured on MS basal medium containing 20.9 μM BA and 5.3 μM NAA. This combination proved to be the best medium for enhanced adventitious shoot bud multiplication, generating a maximum of 50 shoots in 4 wk. This medium was also used successfully for shoot proliferation in liquid medium. Root formation was observed from callus induced in medium containing 8.05–13.4 μM NAA. Regenerated shoots exhibited flowering and root formation in MS basal medium without any growth regulators. Plantlets established in the field showed 85% survival and exhibited identical morphological characteristics as the donor plant.     

Studies on the oviposition and longevity ofIlione albiseta [Dipt.: Sciomyzidae] — Potential biological control agent of liver fluke

The effect of 5 constant temperatures (10, 14, 17, 20 and 23°C) on the oviposition and longevity ofIlione albiseta was investigated. Most eggs were laid at 14–17°C and mean oviposition period declined progressively above and below 14°C. There was no significant difference between oviposition rates or preoviposition periods at each constant temperature, but the mean number of days between egg laying for each female was significantly greater at 10 °C than at 17, 20 and 23 °C than at 20 °C. The percentage of infertile eggs laid ranged from 9.2% at 23 °C to 17.9 % at 20 °C and these eggs tended to be laid at the beginning and end of each oviposition period. A possible association between sex ratio of the emergent adult and temperature is also discussed.