Host plant quality is a key determinant of the fecundity of herbivorous insects. Components of host plant quality (such as carbon, nitrogen, and defensive metabolites) directly affect potential and achieved herbivore fecundity. The responses of insect herbivores to changes in host plant quality vary within and between feeding guilds. Host plant quality also affects insect reproductive strategies: Egg size and quality, the allocation of resources to eggs, and the choice of oviposition sites may all be influenced by plant quality, as may egg or embryo resorption on poor-quality hosts. Many insect herbivores change the quality of their host plants, affecting both inter- and intraspecific interactions. Higher-trophic level interactions, such as the performance of predators and parasitoids, may also be affected by host plant quality. We conclude that host plant quality affects the fecundity of herbivorous insects at both the individual and the population scale.

Host plant quality and fecundity in herbivorous insects

A tool changer is disclosed for automatically removing a working tool after having been used from the spindle of a machine tool such as a vertical milling machine, transferring the used working tool to a rack which stores a plurality of working tools, picking up from the rack another working tool for the next machining operation, transferring such new working tool to the spindle, and operatively mounting such new working tool on the spindle.

Temperature and Organism Size—A Biological Law for Ectotherms?

A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

The relationship between intra-specific variation in female body size and potential fecundity was investigated using the published literature on 57 oviparous species of Coleoptera, Diptera, Ephemeroptera, Heteroptera, Homoptera, Hymenoptera, Lepidoptera, and Trichoptera, and 11 species of larviparous Aphidina and Diptera. Female body sizes were converted to dry body weight. Variation in body weight and fecundity was expressed as percentage deviation from the median values. The increase in fecundity with body weight was similar in most taxa, with only a few important exceptions. The common regression for oviparous and larviparous species predicts a 0.95% increase in median fecundity for each 1% increase in dry body weight. The number of ovarioles (in 10 species of Coleoptera, Diptera, Hymenoptera and Orthoptera) also increased with body weight. The general relationship predicted a 0.81% increase in ovariole number for each 1% increase in dry body weight. The slope of ovariole number versus weight relationship was greater in species with many ovarioles than in species with few. The common slope of the fecundity/size relationship is close to 1 and this indicates that female size is a principal constraint on insect potential fecundity.

https://www.jstor.org/stable/pdfplus/3544943.pdf

Intraspecific variation in body size and fecundity in insects: a general relationship

Mathematical Handbook for Scientists and Engineers

Temporal changes in aphid abundance pose a considerable challenge to ovipositing aphidophagous ladybirds, as in order to maximize their fitness they need to synchronize their reproduction with the early development of aphid populations. Field census data and laboratory experiments were used to determine how ovipositing females of the two-spot ladybird, Adalia bipunctata (L.), assess whether an aphid population is suitable for exploitation. In the field, two-spot ladybirds usually laid eggs well before aphid populations peaked in abundance. In the laboratory they showed a marked reduction in their reproductive numerical response in the presence of larvae of their own species but not of other aphidophagous ladybirds. At the highest aphid density this was not a consequence of competition for food between larvae and ovipositing females. In the presence of conspecific larvae gravid females were very active and as a consequence more likely to leave an area, and when confined with other conspecific females or larvae laid fewer eggs and later than females kept on their own. The extent of the inhibition of egg laying is negatively correlated with the rate of encounter with larvae. Thus it is proposed that gravid females appear mainly to use the presence of conspecific larvae to assess the potential of an aphid colony for supporting the development of their offspring.

Attack strategy of ladybird beetles (Coccinellidae): factors shaping their numerical response

The biology and pest status of Rhopalosiphum padi (L.) in Europe are critically reviewed. New data are presented and the temporal occurrence of the aphid and its host-plants considered. In Britain, R. padi is a pest mainly because of its ability to transmit virus diseases, in particular barley yellow dwarf virus. In other European countries, especially in Scandinavia, R. padi is a pest in its own right. Predator and parasite complexes in Britain and Finland are compared and contrasted. The occurrence of R. padi as a pest of cereals in Europe is compared with that of Sitobion avenae (F.) and Metopolophium dirhodum (Walker). It is postulated that the great abundance of the primary host of R. padi, bird cherry (Prunus padus), and the spring planting of cereals in colder climates such as in Finland are major factors contributing to the differences in pest status of this aphid between Britain and in Scandinavia.

Factors determining the pest status of the bird cherry-oat aphid, Rhopalo-siphum padi (L.) (Hemiptera: Aphididae), in Europe: a study and review

SUMMARY (1) Individuals of six species of aphid from two families were dissected and the number of ovarioles recorded. Variation in ovariole number occurred within and between generations. The spring generation(s) in each species had the highest number. (2) Generations with many ovarioles were more fecund than those with few. In those generations showing variability an individual with a high number of ovarioles was potentially more fecund and reproduced at a greater rate than individuals with few ovarioles. (3) The changes in reproductive potential are programmed and anticipate predictable

Seasonal variation in reproductive potential: a programmed feature of aphid life cycles.

Birth weight and food quality had a positive effect on adult weight, while temperature had a negative effect when the aphids were reared on high quality food, but no effect when reared on low quality food. Size was a consequence of the relative effect of birth weight, nutrition and temperature on developmental and growth rates.



ZUSAMMENFASSUNG

Faktoren, welche die Grosse von Blattlausen beeinflussen, mit besonderer Berucksichtigung der Schwarzen Bohnenlaus, Aphis fabae



Das Geburtsgewicht und die Nahrungsqualitat hatte einen positiven Effekt auf das Gewicht der Adulten. Dagegen hatte die Temperatur einen negativen Effekt, wenn die Blattlause auf guter Nahrung und keinen Effekt, wenn sie auf schlechter Nahrung gezogen wurden. Die Grosse der Blattlause war eine Folge der Effekte von Geburtsgewicht. Ernahrung und Temperatur auf die Entwicklung und auf die Wachstumsgeschwindigkeit.

A. F. G. Dixon

Papers

Attack strategy of ladybird beetles (Coccinellidae): factors shaping their numerical response

Factors determining the pest status of the bird cherry-oat aphid, Rhopalo-siphum padi (L.) (Hemiptera: Aphididae), in Europe: a study and review

Seasonal variation in reproductive potential: a programmed feature of aphid life cycles.

Factors affecting size in aphids with particular reference to the black bean aphid, aphis fabae

Crop loss assessment.