T.E. Mittler

Studies on the artificial feeding of the aphid Myzus persicae (Sulzer)—IV. Requirements for water-soluble vitamins and ascorbic acid

Abstract By means of growth experiments using synthetic diets from which individual vitamins were omitted, Myzus persicae was shown to require a dietary source of ascorbic acid and nine water-soluble vitamins: thiamin, riboflavin, nicotinic acid, pyridoxin, folic acid, calcium pantothenate, meso-inositol, choline, and biotin. In all cases the plant-reared mothers of experimental larvae were themselves maintained on the deficient diets for a few days preceding birth of experimental larvae, in order to deplete larvae of maternally derived stores of the particular vitamin being tested. Under these circumstances, deprivation of thiamin, nicotinic acid, and calcium pantothenate greatly reduced first-generation larval growth and prevented the development of mature adults. Individual omission of the other vitamins markedly reduced first-generation growth but did not prevent development to the adult stage. However, in experiments continued through the second generation, little growth occurred in the absence of any of the vitamins. Since anomalies which occurred in the dosage response to ascorbic acid suggested that this easily oxidized nutrient might be deteriorating in diets, a study was made of ascorbic acid loss from diet kept under various conditions approximating to those involved in experimental use and storage. Loss was rapid at experimental temperatures, less so under refrigeration at +5°C, and largely prevented by continuous frozen storage at −20°C. Considerable losses occurred if frozen storage was interrupted by thawing to room temperature for as little as an hour per day. These findings are discussed in relation to the importance of stringent care in the pre-experimental storage of diets that may contain labile nutrients.

Osmoregulation by the aphid Myzus persicae: A physiological role for honeydew oligosaccharides

The dry matter content of honeydew produced by Myzus persicae feeding on artificial diets increased with increasing sucrose concentrations of the diet. Whereas the diet osmolalities ranged from 828 to 1800 milliosmolal, the honeydew osmolality was relatively constant (about 500 milliosmolal). This osmoregulatory capacity is achieved largely by variations in the mean molecular weight of glucose-containing honeydew oligosaccharides.

Studies on the artificial feeding of the aphid Myzus persicae (Sulzer)—I. Relative uptake of water and sucrose solutions

Abstract A method is described for feeding the green peach aphid Myzus persicae (Sulzer) on liquids accessible via artificial membranes of stretched Parafilm ‘M’ (R) . The aphids ingest considerable amounts of water and sugary fluids entirely by their own sucking efforts. A simple colour scoring method is described which is convenient for routinely assessing the relative uptake by the aphids of various diets. The numbers and kinds of salivations produced by the aphids when penetrating and feeding through membranes are related to the amount of liquid imbibed. The numbers of larvae born to adult apterous aphids are dependent on both the amount of fluid imbibed and its composition. Probing and associated feeding behaviour under the artificial feeding conditions is discussed in relation to the normal feeding behaviour of aphids on their host plants. On the basis of the different criteria of uptake considered in this study, sucrose is distinctly phagostimulatory to M. persicae , 10 to 20 per cent being the optimal concentration range.

Studies on the artificial feeding of the aphid Myzus persicae (Sulzer)—III. Some major nutritional requirements

The development of synthetic diets on which both apteriform and alatiform larvae of Myzus persicae (Sulzer) could be reared to the adult stage is discussed. By the deletion or modification in concentration of particular dietary components, their effects on larval growth and on adult survival and larviposition were determined. Sugar was essential for survival, and sucrose concentrations between 10 and 20% were optimal for both larvae and adults. Larval growth was good with concentrations between 212 and 40% of sugar, but with adults, survival and larviposition deteriorated markedly with concentrations below 10%. No larval growth occurred without amino acids in the diet; with less than 2 per cent of amino acids growth rates fell sharply, the optimal level being about 3 per cent of the diet. The longevity of adults was unaffected by the absence of amino acids, but high rates of larviposition depended upon their presence; a maximal effect on larviposition was achieved with 0·5 per cent of amino acids in the diet. No larval growth occurred if either of the two salts in the diet were omitted, owing to stringent requirements for potassium, magnesium, and phosphorus; adult survival and larviposition were adversely affected if any of these were omitted. A requirement for water-soluble vitamins could be demonstrated only in larvae from parents which had themselves been maintained on the vitamin-deficient regime before bearing the larvae. Under these circumstances, the deleterious effect of vitamin deprivation on the larvae was shown to depend upon the duration of prior maternal deprivation. Apterous adults reared from birth on synthetic diet were able to deposit a small number of live larvae, but these were unable to grow and develop properly although many lived for considerable periods. Adults reared from birth on diet and then transferred to plants deposited larvae which grew and developed normally. From this it is argued that a comparatively simple deficiency condition is involved in the failure of diet-reared aphids to reproduce. The foregoing nutritional information is discussed in relation to the circumstance that the same major dietarily essential components also play an important role in phagostimulation, and the bearing of this on ideas about the relationship of aphids to their natural host plants is considered.

Effect of artificial diet composition on wing-production by the aphid Myzus persicae

Abstract Groups of plant-reared adult apterous Myzus persicae were fed for 1 week on artificial diets differing in the concentration of sucrose, all amino acids, methionine, magnesium chloride, monobasic potassium phosphate, vitamins, trace minerals, and ascorbic acid. The larvae deposited were allowed to develop on the same diets as their mothers received. The proportions of winged individuals among the progeny deposited on each of the 7 days, as well as the growth of these larvae, was markedly effected by the concentrations of the diet. In general, the mothers responded to imbalanced diets by producing a greater proportion of apterous offspring than on a diet on which larval growth was optimal. Thus, except on diets lacking vitamins, trace minerals (EDTA complexes), or ascorbic acid, poor larval growth was associated with the production of apterous rather than alate progeny by their mothers. On diets containing ascorbic acid and the EDTA complexes, a temporary increase in aptera-production was observed and related to similar increases in aptera-production by mothers that were temporarily starved or deprived of all nutrients other than sucrose and water. The results appear to contradict the generally accepted concept that alata-production is enhanced by poor nutrition.

Wing development and parthenogenesis induced in progenies of kinoprene-treated gynoparae of Aphis fabae and Myzus persicae

Abstract Presumptive gynoparae of Aphis fabae and Myzus persicae were exposed to various levels of kinoprene (Zoecons ZR 777) by being placed as 4th-instar alatiform larvae on bean or radish seedlings that had been sprayed with different concentrations of kinoprene in an acetone-tween-water emulsion. Larvae exposed to the highest (0.1%) concentration tested developed into adults 1 to 2 days sooner than those on control plants. The adults on the treated plants had variously deformed wings, reduced sclerotization (and pigmentation in the case of M. persicae) and other apteriform features. On reaching adulthood the affected aphids settled to feed and started to larviposit some days earlier than the control aphids. After two weeks as adults, treated gynoparae of M. persicae produced more larvae than the 7 to 9 typically deposited by control gynoparae under the short-day and cool temperature conditions employed in these tests. Whereas most or all of the larvae produced by the control gynoparae developed into oviparae (apterous, egg-laying, sexual females), gynoparae exposed to 0.1% kinoprene-treated plants predominantly produced alatiform viviparous offspring. If the latter were allowed to develop on untreated plants they deposited a few oviparous larvae. Alatiform virginoparae of M. persicae (from the same holocyclic strain that produced the gynoparae) also responded to kinoprene by developing wing deformities and by producing alatiform offspring. In contrast, alatiform virginoparae from an androcyclic strain of M. persicae, although developing wing deformities, produced only apterous progeny. The stimulation by kinoprene of wing development and parthenogenesis in the progeny of treated gynoparae is discussed in the light of our present knowledge of these aspects of aphid polymorphism.

Utilization of dehydroascorbic acid and some related compounds by the aphid Myzus persicae feeding on an improved diet

Abstract Modifications are described in the formulation of an artificial diet for rearing Myzus persicae. Using this aphid species and the dietary improvements, we determined the relative growth of larvae, derived from ascorbic acid-deprived apterous mothers, on diets containing ascorbic acid or related compounds at various concentrations. l -Dehydroascorbic acid (the oxidized form of l -ascorbic acid) is utilizable, but only about 50 per cent as efficiently as equivalent amounts of l -ascorbic acid. d -Araboascorbic acid (an epimer of l -ascorbic acid about C5) is almost equivalent to l -ascorbic acid. d -Glucurono-γ-lactone and l -gulono-γ-lactone (intermediates in the biosynthesis of ascorbic acid in some mammals) are not utilized to any extent, nor was reduced glutathione (an unrelated reducing substance). The results are discussed in relation to the enzyme specificity and biosynthetic capabilities of other insects and animals.

Influence of larval dietary supply on the food consumption, food utilization efficiency, growth and development of the lacewing Chrysoperla carnea

Larvae of the common green lacewing, Chrysoperla carnea (Stephens)(Neuroptera: Chrysopidae), were fed either an optimal or a suboptimal number of eggs of the moth Anagasta kuehniella (Zeller) in the first and/or second larval instar, or in all three larval instars. Parameters for the duration, growth, and the efficiency of conversion of ingested food to body substance (ECI) of each instar were established for seven different dietary regimes. Larvae that had a suboptimal food supply in the first instar had a significantly longer developmental time, gained significantly less weight, and had a slightly lower ECI in that instar larvae. Suboptimally‐fed second less, but remained only slightly longer in that instar and had a similar ECI to optimally‐fed second instar larvae. The developmental time of suboptimally‐fed third instar larvae was similar to that of optimally‐fed larvae of that stage. Whereas the growth of the former was significantly less than that of larvae optimally fed in that instar, the ECI of the former was significantly higher. Despite the relatively smaller size of larvae fed suboptimally in the first and/or second instar, when such larvae were subsequently supplied with an overabundance of prey eggs, they consumed approximately the same number of eggs during the remainder of their larval life as did larvae whose food supply had not been restricted previously. When larvae were allowed to consume different numbers of eggs in their third instar, their gain in weight and therefore the weights attained by the resulting adults (based on the weights of 3‐day‐old cocoons) had a highly significant positive correlation with the number of eggs consumed in this instar.

Influence of larval food consumption on the fecundity of the lacewing Chrysoperla carnea

The effects of food consumption on larval growth and development and adult fecundity of the common green lacewing, Chrysoperla carnea (Stephens), were studied on two populations of larvae derived from either a laboratory colony or from field‐collected adults. The number of eggs of the Mediterranean flour moth, Anagasta kuehniella (Zeller), provided to individual lacewing larvae was varied to produce three food‐supply treatments: low, intermediate, and high. Food‐supply was found to influence larval growth and development and adult fecundity. Lacewing larvae provided with an overabundance of moth eggs developed faster than larvae provided with fewer moth eggs than they could have consumed. Adult females that developed from the high feeding treatment had a substantially shorter preoviposition period, a later decline in egg deposition, and a significantly higher fecundity than adults arising from the other feeding classes. Unrestricted feeding by adult lacewings on an artificial diet did not compensate for prior low feeding regimes. The overall performance of the lacewings derived from the laboratory colony was substantially poorer than that of the lacewings derived from field‐collected adults. This effect was accentuated when the larvae were given a low food‐supply. This overall decrease in vigor is attributed to inbreeding of the laboratory culture over a one year period. These finds are relevant to mass rearing programs for this biological control agent.

An aphid circadian rhythm: factors affecting the release of sex pheromone by oviparae of the greenbug, Schizaphis graminum.

Abstract Adult oviparae of Schizaphis graminum emit a sex pheromone from scent plaques on the metathoracic tibiae, as do oviparae of other aphid species. By allowing males to walk along a wire walkway, a turning response and an increased rate of antennation were observed when the aphids were within 1–2 cm of a pheromone source. Adult males responded but 4th instar larval males did not. The onset of the release of the pheromone by the oviparae is triggered by the initiation of the light phase in a LD-cycle, and is governed by a circadian rhythm with a free-running period of 25.6 hr under continuous illumination of 15 lx. Daily pheromone release peaks 4–7 hr after lights-on and reaches a maximum on days 6–8 of adulthood.