Effects of food quality,particularly nitrogen concentrations,of Eucalyptus blakelyi foliage on the growth of Paropsis atomaria larvae (Coleoptera: Chrysomelidae)

Five groups of E. blakelyi seedlings were differentially fertilized to obtain a range of N concentrations from 0.8–3.0% dry wt in the foliage. Groups of P. atomaria larvae were reared from eclosion to the prepupal stage on these seedlings. The effects on larval growth and development caused by foliar concentrations of N, moisture content, and tannins and leaf toughness were measured. Pupal dry weight and development time of P. atomaria did not differ between those reared on foliage with N levels of 1.7–3.0% but there was a significant decrease in pupal weight and increase in development time for individuals fed foliage with N below this level. Larvae fed foliage with an average of 0.8% N died before reaching instar III. Total dry matter consumption increased with a decrease in N concentration. Larval nitrogen utilization efficiency increased as foliar N level decreased until N reached a level somewhere between 1.7%–1.2% below which it decreased. There appeared to be an N concentration threshold above which P. atomaria larvae received adequate N by regulating consumption and nitrogen utilization efficiency but below which they could no longer accumulate enough N by compensation to maintain an optimum growth rate and development time. Effects of food quality variables on relative growth and consumption rates are presented and discussed.     

Effect of cassava exudate and prey densities on the survival and reproduction of Typhlodromalus limonicus (Garman & McGregor) s.l. (Acari: Phytoseiidae), a predator of the cassava green mite,Mononychellus tanajoa (Bondar) (Acari: Tetranychidae)

The effects of cassava exudate and prey densities on reproduction and survival of the predatory mite, Typhlodromalus limonicus (Garman & McGregor) (Acari: Phytoseiidae), were investigated in the laboratory. Females were provided either cassava exudate ad lib. daily, low or high numbers of the cassava green mite prey, Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) daily, or exudate for 5 or 10 days before switching to a low or high prey diet. Females fed only exudate laid no eggs. Females fed exudate before prey experienced a significant decrease (30%) in the number of eggs laid compared to females fed high numbers of prey daily. The reduction in fecundity was the result of prolonged preoviposition periods (2.0 days on prey daily vs 4.0 days on exudate before prey) and reduced number of eggs laid per female per day (1.7 eggs per female per day on prey daily vs 0.4 eggs per female per day on exudate before prey). Females fed only exudate had a greater survival rate and longevity than females fed prey daily or females fed exudate before a diet of prey. These results suggest that T. limonicus can survice for a limited period on cassava exudate during periods of low prey availability, but requires prey to complete oögenesis and propagate the population.     

Larviposition in the ovoviviparous blowfly Calliphora dubia

This study examined larviposition in Calliphora dubia Macquart (Diptera: Calliphoridae), an ovoviviparous blowfly of considerable forensic importance in Australia. Females in the field carried 22–83 live larvae, exhibiting a strong linear relationship between female size and the number of live larvae carried. Females took just over 1 min (mean 67.7 ± 7.7 s, n = 54) to larviposit live larvae on or near fresh liver in the laboratory. Females laid larvae at a mean rate of 1.2 ± 0.1 larvae/s, with the fastest rate being 3.4 larvae/s. Most females (70%) laid live larvae only, but 14% laid larvae and eggs at the same time and 16% laid eggs only (none of the eggs laid were viable). Females laying only live larvae laid a mean of 53.7 ± 2.3 larvae, whereas those laying only eggs laid a mean of 48.6 ± 2.8 eggs on each occasion. None of the eggs laid were viable. Most females (86%) laid all their larvae in a single spot, even if they engaged in several bouts of laying live larvae. Nearly one‐third of females did not lay all the live larvae in their ovisacs, but retained half of their complement of developed larvae. Females may be opting to spread their larvae across several carcasses in order to increase their survival and not to overcrowd small, ephemeral carcasses. The fact that a blowfly can lay either eggs or live larvae has enormous implications for the accurate determination of the post‐mortem interval (PMI) as the presence of larvae derived from eggs laid on the body add 6–18 h to the PMI. This paper represents the first report of the ability of female calliphorids to resorb some of their own live larvae.     

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.     

Protein consumption by mated, unmated, sterile and fertile adults of the Queensland fruit fly, Bactrocera tryoni and its relation to egg production

Abstract. Female adults of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) at 25 °C require more than 0.1 mg of yeast autolysate per day to mature their oocytes to the vitellogenic stage and mate. Those given 0.2 mg per day from day 2 of adult life mated (when given the opportunity between 11 and 13 days) and each laid approximately 100 eggs (just over one egg per ovariole) by day 56. Females allowed to feed ad libitum from day 2, then 0 or 0.2 mg per day from day 14, laid approximately 75 and 100 eggs, respectively (after mating), whereas those fed ad libitum from day 2 to day 56 laid approximately 540 eggs after mating (averaging just over six eggs per ovariole). The developmental pattern of intake of normal females when on an ad libitum diet showed a rise to a peak at 5–7 days, followed by a decline to sustained low levels if not mated, but rising to a lower peak if mated between days 11–13 followed by a steady decline. Female flies that had been sterilized by 80 Gy gamma irradiation at the puparial stage had a pattern of food consumption similar to that of normal females mated at 7 days but they produced no yolky oocytes and had a darkened fat body. Normal and irradiated males had a feeding pattern similar to that of unmated nonirradiated females but at a lower level. The results are discussed in terms of the control of protein intake and the rate of its conversion to yolk.     

Limitation of reproduction by feeding condition in a carabid beetle,Carabus yaconinus

1. Effects of the amount of food consumed on reproduction of the carabid beetle, Carabus yaconinus B., were studied in the laboratory by rearing beetles at different food levels, and the feeding and oviposition rates in the field were estimated on the basis of the relationships between the amount of food consumed, body weight and egg production obtained in the experiment.
2. The maximum amount of food consumed was 150 mg of minced beef per day. The number of eggs laid per day and the mean body weight increased with an increase in the amount of food consumed. High mortality occurred only when the beetles consumed less than 25 mg of minced beef per day.
3. The ratio of current body weight to the minimum one just before death by starvation, W/W_min, was used for the estimation of the rates of food consumption and egg production. The relationships between mean W/W_min ratio, the amount of food consumed and the number of eggs laid per day were clarified.
4. The relationships between ovary states (ovary weight and the number of mature eggs in the ovary) and W/W_min ratio were examined for the females caught in the field. Females with higher values of W/W_min ratio had more mature eggs.
5. The amount of food consumed by females in the field during the reproductive period was estimated to be 50–70% of the maximum value attained in the experiment and the estimated rate of oviposition was 45–59% of the maximum rate attained in the experiment.

     

Insect grazing on Eucalyptus in response to variation in leaf tannins and nitrogen

Summary Many species of Eucalyptus, one of the dominant genera in Australian forests and woodlands, contain high levels of tannins and other phenols and are also heavily damaged by grazing insects. These phenols do not appear to affect insect attack because a wide range of concentrations of condensed tannins and other phenols in leaves of 13 Eucalyptus sp. influenced neither feeding rates of Paropsis atomaria larvae, nor their nitrogen use efficiencies. We discuss reasons why tannins may not appreciably reduce the availability of nitrogen (N) to these insects. Performance was directly related to leaf N concentration, and growth rates, N gains, and N use efficiencies all increased as leaf N content increased, although absolute feeding rates remained constant. These relationships differ from those found in insects feeding on other plants, and we suggest that the low N contents common in Eucalyptus leaves may be responsble. We propose that the extensive damage observed in many eucalypts is in part related to the high feeding rates maintained by individual larvae.To whom offprint requests shouid be sent     

Influence of sulphur plant nutrition on oviposition and larval performance of the cabbage root fly

1 Oilseed rape plants (Brassica napus) (L.) (Brassicaceae) were grown under different levels of sulphur supply and tested for the oviposition preference and larval performance of cabbage root flies Delia radicum (L.) (Diptera: Anthomyiidae). 2 Adult females laid more than three‐fold as many eggs on control S_n (normal field concentration) than on sulphur‐free S₀ plants. By contrast, no significant difference was observed between control and double normal concentration (S₊) plants. 3 The larval performance was evaluated using three additional, intermediate sulphur levels between S₀ and S_n, and the plants were infected with equal numbers of eggs. The percentage pupation at the end of larval feeding ranged from 6% (S₀) to 32% (S_n or S₊) and the average number of pupae, or of emerging flies, was significantly correlated with sulphur application. 4 The weight of emerging males and females was correlated with plant sulphur supply. 5 The duration of development from eggs to adult emergence was approximately 2 days longer in females than in males. Females originating from plants with a normal or higher sulphur supply tended to emerge 1–2 days earlier.     

Effects of delayed mating and male mating history on the reproductive potential of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

Abstract 1 Despite the importance of Leucoptera coffeella (Guérin‐Mèneville) in coffee production worldwide, there is a lack of information on its reproduction. This knowledge will help in mass rearing, and support the development of behavioural control techniques for this insect. The present study determined the effects of delayed mating and previous matings of male L. coffeella on fecundity, egg viability and frequency of female remating. 2 The highest levels of fecundity and egg viability were obtained from matings of 1–3‐day‐old females. When females mated at 5 days of age, there were reductions of 40% in oviposition and of 43% in egg viability. 3 Females mated with 2‐day‐old virgin males were more fecund than those mated with older males; egg viability was also low (18%) from females mated with older males. 4 Virgin females that mated with virgin males laid a greater number of eggs than those mated with previously copulated males. Egg viability decreased with the increase in the number of previous male matings. 5 Five‐day‐old females remated in greater proportion than 2–3‐day‐old females. Females that copulated with males that had previously mated three times had higher rates of remating than those that copulated with virgin males. 6 The results obtained indicate that 1–3 days after emergence is the optimum age for mating. The implications of these findings for the control of L. coffeella by synthetic sex pheromone are discussed.     

Oviposition behaviour and response of Monochamus scutellatus (Coleoptera: Cerambycidae) to conspecific eggs and larvae

• 1 The oviposition behaviour of white‐spotted sawyer beetle Monochamus scutellatus (Say) (Coleoptera: Cerambycidae) females was studied under laboratory and field conditions.
• 2 Females walked over the bark surface and stopped to palpate it with their labial and maxillary palpi. Once a potential oviposition site was located, the female excavated a scar in the bark with her mandibles, deposited an egg and brown plug in the scar and inserted her mandibles again into the scar prior to leaving the area.
• 3 Female M. scutellatus preferred to lay eggs on bolts containing no eggs (control) to those containing eggs from other females, but did not show this preference when provided with control bolts and those containing their own eggs. When females were provided with bolts containing their own eggs and bolts containing eggs from other females, they laid more eggs on bolts containing their own eggs. Females laid more eggs on control bolts than on bolts containing their own larvae or larvae from other females.
• 4 The brown plug in the oviposition scar may provide a protective barrier to the egg, a chemical message that the site is occupied, or both.

     

Male Lekking duration and Mating Benefits in a Lek-Forming Hawaiian Drosophila

Variation in lekking duration of males of a Hawaiian Drosophila, D. grimshawi, was examined in laboratory enclosures. The relationship between variation in male lekking activity and number of eggs laid by females, proportion of eggs hatching, and total offspring production was investigated. Females mating highly active males laid fewer eggs and thus had lower offspring production than females mating less active males, even though other studies have shown that D. grimshawi females prefer more active males as mates. These results are discussed in terms of conflict between males and females over mating benefits and in trade-offs faced by males between lekking duration and offspring production per mating. Testis mass was not related to lekking activity levels, but males with heavier testes produced more offspring per mating, suggesting that males may vary in other ways that correlate with possible direct fitness gains for females.     

Host plant conspicuousness and the distribution of eggs and larvae in the butterfly,Anthocharis scolymus (Lepidoptera: Pieridae)

We investigated how the distribution pattern of eggs and larval on the host plant, Turritus glabra, was influenced by the oviposition behavior of the pierid butterfly Anthocharis scolymus. Females searched for the host plants visually and they frequently approached taller host plants with sparse surrounding vegetation. After encountering host plants, oviposition behavior of females was independent of host plant characteristics such as height, density, and type of surrounding vegetation. A female laid eggs singly on a host plants. Most females appeared to lay their eggs regardless of the presense of eggs on the host plant. Consequently egg and larva tended to be abundant on conspicuous host plants as measured by height or relative isolation from other plants. However, overcrowding of eggs on an individual host decreased the survival rate of larvae.     

Do Golden Egg Bugs (Phyllomorpha laciniata: Heteroptera, Coreidae) Require Conspecifics for Oviposition?

Golden egg bug (Phyllomorpha laciniata) females lay eggs on the bodies of conspecifics of both sexes. We investigated to what extent reproduction depended on the availability of conspecifics as oviposition substrate and the acceptability of the host plant as an alternative oviposition substrate in the absence of conspecifics. Mated females were placed in experimental enclosures each containing a sprig of fresh host plant. Each experimental female was subjected to one of three treatments: isolated from conspecifics (solitary), paired with another female, or paired with a male. Solitary females laid a few eggs on the host plant but then stopped laying eggs, and solitary females laid significantly fewer eggs than those enclosed with another female or a male. Females enclosed with a male laid no more eggs than those enclosed with a female. When two previously isolated females were later enclosed together, they soon renewed oviposition. Females in nature contained significantly more oviducal eggs than did females that were enclosed with other females for a short period. Thus the availability of suitable conspecifics as oviposition substrate stimulates the deposition of mature eggs, and reproduction depends on the presence of conspecifics of either sex as oviposition substrate.     

Leaf age and larval performance of the leaf beetle Paropsis atomaria

ABSTRACT.

• 1 Larval performance of the leaf beetle Paropsis atomaria Oliver was determined for larvae raised on both new and mature leaves of Eucalyptus blakelyi Maiden. Larvae were transferred to mature leaves at different ages; control larvae stayed on new leaves through all instars.
• 2 Only larvae reared on new leaves through the third instar survived to pupate on mature leaves; developmental time was prolonged by 20% and pupal weight was reduced by 50% in these larvae compared with larvae reared entirely on new leaves. Almost all larvae died when transferred to mature leaves as first, second or third instars.
• 3 Low survival and slow development on mature leaves was mainly due to failure by larvae to feed. Larvae palpated leaves and could discriminate among leaf ages immediately, without biting into the leaf tissue.
• 4 New leaves had higher concentrations of oil and tannins than old leaves, while there were no significant differences in nitrogen concentrations in the two types of leaves. Mature leaves were more than 3 times tougher than new leaves, in terms of g mm^?2 of penetrometer force.
• 5 In drought years E. blakelyi may not produce sufficient new leaves to supply specialist herbivores with their preferred food resource. We infer that drought years reduce P. atomaria larval performance significantly, and influence the population dynamics of the insect.

     

Predators induce egg retention in prey

To prevent predation on their eggs, prey often avoid patches occupied by predators. As a result, they need to delay oviposition until they reach predator-free patches. Because many species allocate energy to egg production in a continuous fashion, it is not clear what kind of mechanism prey use to delay oviposition. We used females of the phytoseiid mite Neoseiulus cucumeris to study these mechanisms. Females were placed in patches with pollen, a food source they use for egg production, and they were exposed to another phytoseiid mite, Iphiseius degenerans, which is an intraguild predator of N. cucumeris juveniles. We found that the oviposition of N. cucumeris females on patches with the predator was lower than on patches without the predator. Cues left by the intraguild predator were not sufficient to elicit such behaviour. Females of N. cucumeris reduced oviposition when exposed to the predator by retaining the egg inside their body, resulting in a lower developmental rate once these eggs were laid. Hence, females are capable of retaining eggs, but the development of these eggs continues inside the mother’s body. In this way, females gain some time to search for less risky oviposition sites.     

Costs and benefits of host feeding in the parasitoid wasp Trichogramma turkestanica

Females of the parasitoid wasp Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae) generally host feed after ovipositing on the first egg of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) they encounter. We measured the impact of host feeding on the fecundity and longevity of females, in absence of host or food, and on the fitness of their progeny. We also determined if the frequency of host feeding is influenced by the humidity level at which T. turkestanica females developed. Host feeding increased egg production by 70% but decreased female longevity. This impact of host feeding on the longevity of females is probably due to the allocation of carbohydrates to egg production at the expense of somatic maintenance. Humidity did not influence the occurrence or duration of host feeding. The size of individuals developing in eggs on which females host fed was smaller, indicating that their fitness was affected.     

Interaction between Sitona lepidus and red clover lines selected for formononetin content

Adult clover root weevil Sitona lepidus show a feeding preference for white clover Trifolium repens over red clover Trifolium pratense. The effects on S. lepidus of three red clover T. pratense lines, selected for high, medium, or low levels of the isoflavone formononetin in foliage, were compared in three experiments using white clover as a control. In a no‐choice slant board experiment, weevil larval weights were greater for larvae feeding on white clover roots than those feeding on roots of the red clovers. The effect of larval root herbivory on plant growth was similar for all four clovers. Following root herbivory, a large increase in root and shoot formononetin levels was observed in the high‐formononetin selection of red clover but little change in the low‐formononetin red clover. In a no‐choice experiment with sexually mature female adult weevils feeding on foliage of the four clovers, all the red clovers had increased weevil mortality. Female weevils eating the high‐formononetin red clover laid fewer eggs than weevils eating white clover. The red clover diet caused a large accumulation of abdominal fat and/or oil in the weevils, whereas weevils feeding on white clover did not accumulate fat/oil. When sexually immature adult weevils were given a choice of foliage from all four clovers, white clover was eaten preferentially, and the low‐formononetin red clover was preferred to the high‐formononetin red clover. The results suggest that formononetin and associated metabolites in red clover may act as chemical defences against adult S. lepidus and that distribution in forage legumes can be manipulated by plant breeding to improve root health.     

Leaf age and life history variables of a leafminer: the case of Liriomyza trifolii on potato leaves

Field observations and laboratory experiments have demonstrated that infestation by the serpentine leaf miner, Liriomyza trifolii Burgess (Diptera: Agromyzidae), begins in the lower leaves of the potato plant, and proceeds through the middle leaves to those of the upper canopy. In choice and no‐choice experiments, mated adult L. trifolii females were given access for 48 h to potato plants, and caged on differently aged leaves. The extent of their feeding and oviposition on the 5–7 leaflets of the upper, middle, and lower leaves were recorded. The life history variables of the next generation were estimated: percentage egg hatch, number of mines formed, larval survival, number of pupae formed, size and weight of pupae, percentage pupation, number of adults formed, percentage emergence, size and weight of adults, sex ratio, adult longevity, and their reproductive performance. The results showed that L. trifolii females laid fewer eggs on the upper leaves, which were poor hosts for larvae. However, a comparison of oviposition behavior between the middle and lower leaves showed that the data did not fit the oviposition preference–offspring performance hypothesis, which postulates that females preferentially oviposit on hosts on which larvae perform best. Females exhibited a preference for the larger, older, lower leaves, although the middle leaves were superior for the growth and development of the young stages. It is hypothesized that adult ovipositional preference for the older, larger, and thicker leaves of the lower foliage may be influenced by factors other than resource quality for larvae.     

Rhythmicity of mating and oviposition inCallosobruchus subinnotatus (Pic) (Coleoptera: Bruchidae)

Mating and oviposition behaviors were studied inCallosobruchus subinnotatus. Copulation was most frequent during the late scotophase, 2–3 h before onset of photophase. The females were less willing to mate during photophase, which increased the time to initiate mating while decreasing the duration of mating. Females exhibited increased movement prior to mating, resting immediately after mating, and remained stationary for 6 h when oviposition commenced. Multiple mating by both males and females affected the number of eggs laid, duration of mating, and uncoupling time at the end of mating. Females that mated two or three times laid more eggs than females that mated once or more than three times. Females that remainedin copula for less than 18 min showed greater readiness to remate than those that remainedin copula longer. There was a gradual decrease in the number of eggs females could lay with an increase in the number of previous matings by males.     

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.