A. S. Schoeman

Are non‐reproductive male highveld mole‐rats, Cryptomys hottentotus pretoriae physiologically suppressed while in the confines of the natal colony?

The highveld mole-rat, Cryptomys hottentous pretoriae is a social, subterranean, co-operative breeder with a high reproductive skew. The relationship between reproductive status and reproductive physiology in male highveld mole-rats was investigated. Testicular morphometrics, histological parameters, plasma testosterone concentrations and sperm motility parameters were studied in 31 males (14 reproductive and 17 non-reproductive males). Reproductive males were significantly larger than non-reproductive males, with testicular mass and volume corrected for body mass considerably larger for the reproductive males. Circulating plasma testosterone concentrations of reproductive males were not significantly higher than non-reproductive males (reproductive males 10.3±1.8 nmol l−1vs non-reproductive males 7.3±1.74 nmol l−1). Sperm motility parameters were measured, but no significant differences were found between reproductive and non-reproductive males. All 14 reproductive males had motile sperm, whereas 13 of the 17 (76%) of non-reproductive males possessed motile sperm. A typical ejaculate of a reproductive male contains 48.3% motile sperm characterized by a high percentage of flagellar defects, whereas the non-reproductive male has an ejaculate containing 45.6% motile sperm with a high percentage of head defects. It is apparent that non-reproductive males are not physiologically suppressed from reproducing. Moreover, the non-reproductive males are excluded from incestuous matings as a result of being the offspring of the reproductive female.

The toxicity of five insecticides to earthworms of the Pheretima group, using an artificial soil test

An artificial soil test was used to assess the toxicity of five insecticides, used for turfgrass pest management, to earthworms of the Pheretima group (Megascolecidae). The effects of cyfluthrin, carbaryl, chlorpyrifos, fipronil and imidacloprid on earthworm mortality, earthworm biomass and individual earthworm mass, were assessed. Carbaryl and chlorpyrifos had a significant greater effect on earthworm mortality than cyfluthrin, seven days after the application of the insecticides. No other significant earthworm mortality was found. None of the insecticides had a significant influence on earthworm biomass. Cyfluthrin initially reduced individual earthworm mass, but not biomass, more than the other insecticides. Carbaryl reduced biomass more than the other insecticides for all the assessments. Carbaryl, imidacloprid and cyfluthrin had a larger negative effect than the control, fipronil and chlorpyrifos on individual earthworm mass in the 14 and 21 day assessments. © 2000 Society of Chemical Industry

Efficacy of pseudostem and pheromone seasonal trapping of the banana weevil Cosmopolites sordidus in South Africa

Abstract The banana weevil (Cosmopolites sordidus) is an important pest of bananas (Musaceae: Musa species) in South Africa. Adult trapping methods were compared in field trials using a randomised block design. Pseudostem traps, pitfall traps containing a pheromone (either Cosmolure® (Pheromone A) or Cosmolure+® (Pheromone B)), and unbaited pitfall traps (control), were compared over 5 weeks during all seasons along the Southeast coast of South Africa. Pseudostem traps treated with an insecticide, and rhizome traps, were included as additional treatments in autumn. In summer two treatments were also added: individual suspension of both pheromones above a pitfall trap either in combination with or without a pseudostem trap. The adult beetles were sexed, and the number of internal eggs noted. Pheromone A proved to be the most effective of the different pheromone lures. Grouping of the pheromones resulted in a synergistic response, while combining the pseudostem did not enhance trap efficacy. The different plant material traps and the control were usually equally effective in catching weevils. Plant material traps caught greater numbers of fecund females, but pheromone traps captured a higher proportion of females. Treatment effects were much less pronounced in summer, and compared to a pseudostem trap, pitfall traps were the most efficacious during spring. Compared to conventional pseudostem trapping, Pheromone A pitfall traps should be optimally applied during spring in South Africa.

Laboratory evaluation of lufenuron on immature stages of potato tuber moth (Lepidoptera: Gelechiidae).

Abstract The effects of the chitin synthesis inhibitor lufenuron againstpotato tuber moth, Phthorimaea operculella (Zeller), eggswere determined by topically exposing different age groups of eggs(1–4 d old) to treated potato tubers (Solanum tuberosum L.)under laboratory conditions. Larval hatch from both treated (4 and12 g [AI]/100 liter) and untreated tubers was >95%, butmortality of first instars was high in treated tubers (>90%) comparedwith untreated tubers. Examination of the treated tubers showed thatmost of the larvae were unable to penetrate or cause any noticeabledamage to the potato tubers. However, the few first instars thatsurvived were able to penetrate the tubers and continue theirdevelopment to the pupal or adult stages. At 12 g (AI)/100 liter,adult emergence was <2% and most of the emerged adults hadmorphological deformities such as reduced wing size and they wereunable to free themselves from the pupal sacs. These data suggest thattopical application of lufenuron to eggs before larval hatch wouldreduce the amount of damage caused by potato tuber moth as part ofintegrated pest management program.

RELATIVE AGE AND REPRODUCTIVE STATUS IN CRYPTOMYS HOTTENTOTUS PRETORIAE (RODENTIA: BATHYERGIDAE) FROM SOUTH AFRICA

Abstract The degree of molar eruption and wear were used to assign individuals of the social highveld mole-rat (Cryptomys hottentotus pretoriae) from South Africa into 9 relative age classes. Reproductive animals were found to be the oldest and heaviest members of colonies. Cranial morphometric analysis of 4 geographically disparate populations in South Africa generally showed lack of sexual dimorphism in cranial characteristics, but revealed 2 distinct groupings among the 9 relative age classes. The 1st grouping comprised individuals of age classes 1–4, which were all nonreproductive animals and considered to represent a combination of juveniles and subadults. The 2nd grouping included individuals of age classes 7–9, which included reproductive animals. Individuals of age classes 5 and 6, however, were largely intermediate, with some individuals included among both the younger and older age classes, but only a few of these animals were reproductive. These groupings suggest that if age classes are visualized as demarcating sections of variable and unknown length on a hypothetical growth curve, then individuals of age classes 5 and 6 appear to fall at a point on the curve just before it begins to stabilize. These results, together with a proposed microsatellite study, have the potential to provide additional tools to improve our current understanding of social structuring within colonies of the highveld mole-rat.

Aseasonal reproduction in the Hottentot golden mole, Amblysomus hottentotus (Afrosoricida: Chrysochloridae) from KwaZulu-Natal, South Africa

The Hottentot golden mole, Amblysomus hottentotus, is a subterranean mammal that exhibits aseasonal breeding. Reproductive organs of golden moles that had been killed on a monthly basis over a period of one year were examined. Reproductive tract measurements and body mass of each individual was measured and ovarian and testicular histology investigated. Body mass of males was significantly higher than that of females. Ovarian and testicular volume as well as seminiferous tubule diameter did not vary statistically on a seasonal basis. Graafian follicles and corpora lutea were present in the ovaries for nine months of the year, suggesting that ovulation can occur in any month. Despite the lack of seasonality, there appears to be enhanced follicular development during the warm, wet summer months. The litters tend to be small, mean ± S.E.: 2.0 ± 0.1 (range 1.0–3.0).

Efficacy of cultural control measures against the banana weevil, Cosmopolites sordidus (Germar), in South Africa

The banana weevil, Cosmopolites sordidus, is the most important insect pest of banana and plantain in the world. Cultural control methods were investigated over 2 years in southern KwaZulu‐Natal, South Africa. Harvesting at ground level and dissection of remnants (treatment 1), and covering the base of the mat (entire plant consisting of several meristems) with soil and moving debris to the inter‐row (treatment 2), were compared to a positive control that involved treatment of plants with a registered pesticide (treatment 3), and a negative control that involved harvesting at 150 cm from the collar with no soil or sanitation amendments (treatment 4). Yield, weevil damage and pseudostem girth of plants were measured from August to November annually, while adult beetle densities were assessed over 4 weeks in October/November and April. Nematode samples were taken and analysed in October/November every year. Damage parameters included the coefficient of infestation, the percentage coefficient of infestation (PCI) at two intervals, the summed PCI value, the percentage cross‐sectional damage of the central cylinder and cortex, and the mean cross‐sectional damage percentage. A randomized block design with three replicates was used in the trial. The parameters were similar before the onset of the trial. Fruit yield and plant girth, corrected by nematode densities, were not significantly different in any treatment, nor were the nematodes controlled. Soil cover and recession of remnants was the only effective treatment, significantly reducing the CI, but not the adult density or the other damage parameters. Soil cover showed promise as a cultural control method because it only needs to be applied seasonally and reduced the percentage cross‐sectional damage of the central cylinder, the damage parameter most closely related to yield, by 14%.

STRIDULATION OF GRYLLOTALPA AFRICANA (ORTHOPTERA: GRYLLOTALPIDAE) ON TURF GRASS IN SOUTH AFRICA

Abstract During spring to autumn, Gryllotalpa africana males stridulate and produce phonotactic calling songs from specially constructed acoustical burrows. Songs start just after dusk and continue for several hours. The characteristics of the trilling song and sound pressure levels produced were investigated by near field digital recordings made during autumn 2002 and spring 2002 with soil temperatures noted by measuring sound pressures beyond the near field with a sound level meter in spring 2002, respectively. The carrier frequency (2.161-2.477 kHz) and syllable duration (7.340-12.078 ms) of calls showed no significant relationship with soil temperature and no significant differences between autumn and spring with soil temperature constant. Syllable period (10.455-17.221 ms) and inter syllable interval (1.912-9.607 ms) were significantly negatively correlated with soil temperature, and with the latter constant, significantly longer in spring than in autumn. The syllable repetition rate (0.058-0.096 syllables/ms) and duty cycle (43.31-81.72%) showed a significant positive relationship with soil temperature and significant decrease in values with soil temperature constant in spring relative to autumn. Sound pressure levels (re. 20 μPa) at 200 mm from the burrow varied from 77.6 to 89.8 dB.

Seasonal development of Gryllotalpa africana (Orthoptera: Gryllotalpidae) on turfgrass in South Africa

Abstract The population dynamics (in terms of seasonal development) of Gryllotalpa africana Palisot de Beauvois was documented for the first time in South Africa. An irritant drench (soapy water solution) was used to quantify life stage occurrence on turfgrass over a one-year period. Oviposition took place from early October (spring), with eggs incubating for approximately three weeks. Nymphs reached the adult stage from March (late summer) and most individuals overwintered in this stage. Adult numbers peaked in early September (early spring), declining through spring. G. africana was therefore univoltine in the study area. The adult population was female biased in spring. The smallest nymphs and adults (in relation to mean length) were collected in December (early summer), while the smallest nymphs (in relation to mean length) occurred in November (late spring).

Flight Patterns of Gryllotalpa africana (Orthoptera: Gryllotalpidae) in South Africa

Abstract Flights of univoltine mole crickets are usually female biased and peak during spring and autumn. A male Gryllotalpa africana Palisot de Beauvois song recording was broadcast weekly at 93.7 dB (200 mm from speakers, 20 μPa) just after sunset for 1.5 h over an annual period. Attracted individuals (conspecifics) were sexed and females were dissected. Temperatures were measured at each sampling date, and moon phase was recorded. Adult G. africana flew to the song broadcast from spring to autumn, with activity peaking mid-spring and again in late summer to early autumn. Spring flights were characterized by a significant female bias, whereas sexes were present in equal proportions during summer and autumn. The monthly sex ratio of flying individuals was not significantly different from that of mole crickets sampled in the field. Flying females were only reproductively mature in spring to early summer and contained eggs beginning in late spring. Eggs per flying female declined into summer. Flight activity and gender of G. africana were significantly positively related to temperature, with air temperature showing the highest degree of correlation. Moon phase showed no significant relationship with the total number of flying individuals or that of genders.