The following two species of Encyrtidae are recorded for the first time as parasites of Antonina graminis (Maskell) from South Africa: Neodusmetia sangwani (Subba Rao), originally known from India, and Stemmatosteres primus, which is descriptionbed as new.
The spotted alfalfa aphid, T. trifolii f. maculata, is regarded as a variant form of the yellow clover aphid, T. trifolii, which is indigenous to Europe, northern Africa, the Middle East, Afghanistan and India. It has become established in the USA, eastern Canada, Mexico and, more recently, Australia and South Africa. In Australia it was first discovered on 29 March 1977 in Queensland and on 10 May 1977 in South Australia. An account is given of its spread to all the lucerne-growing areas in South Australia within a year of discovery. Factors influencing the spread of the aphid are discussed.
At constant temperatures of 20, 25, 30, and 35ï¿½C, the incubation periods ranged from 6,7 to 2,1 days, the larval periods from 43,9 to 20,8, the prepupal periods from over 10 to 4, and the pupal periods from 11,1 to 6,0 (no pupae formed at 20ï¿½C). Females kept at 35 ï¿½C laid fewer eggs (mean 605) than those kept at the lower temperatures (1129-1464). Egg mass was inversely related to temperature (0.33 mg at 20 ï¿½C, 0,18 mg at 35ï¿½C).
Zebra stripes have traditionally been thought of as an adaptation against detection by vertebrate predators, such as lions and hyaenas. A different hypothesis is suggested: that the stripes are an adaptation against visually orienting biting flies and act by obliterating the stimulus presented by a large dark form, which is important in host-finding by many Diptera. This hypothesis is supported by some indirect evidence and by a field experiment which compares fly catches on moving and stationary black, white and striped models. Striped models caught significantly fewer tsetse and other flies than solid black or white models, but this difference was much reduced in the presence of olfactory attractants.
Copidosoma koehleri Blanchard and Apanteles subandinus Blanchard were introduced into South Africa in 1965-69 and now account for about 90% of parasitism of tuber-moth larvae in potato fields. Every year they undergo a cyclical change in relative numbers. Copidosoma predominates in the first generation of larvae in September (spring), but is rapidly superseded by Apanteles, which predominates from October to December. Thereafter, Copidosoma overtakes Apanteles and comes to outnumber it by about 4:1 in February.
A method of rearing Cinara cronartii in the laboratory on freshly cut pine logs is descriptionbed. At 23 ï¿½C, 50-70% R. H., and 16-h day-length the nymphs reached maturity in about 9 days. Only two adult morphs of C. cronartii occur in South Africa, apterous and alate viviparae. On average, apterous females lived for 21 days and produced 67 nymphs during that time, alate females lived for 19 days and produced 40 nymphs. Ovulation did not occur in adults, and the number of embryos in the ovaries at final moult accurately reflected the fecundity of the apterae, The numbers of ovarioles in the ovaries ranged from 10 to 14 for apterae and from 10 to 12 for alatae. Aphids from the same colonies usually had the same number of ovarioles.
Predators of larvae of the sugarcane borer Eldana saccharina Walker were identified by a serological technique called cross-over electrophoresis. Tests were conducted on the stomach contents of 1521 arthropods, which were collected from sugarcane fields in two regions; one where the density of the pest was high, and the other where the density was low. Ants and spiders were the commonest predators. Members of these taxa were the most abundant predacious arthropods associated with sugarcane in Natal.