Kok-Boon Neoh

Do Termites Avoid Carcasses? Behavioral Responses Depend on the Nature of the Carcasses

Background Undertaking behavior is a significant adaptation to social life in enclosed nests. Workers are known to remove dead colony members from the nest. Such behavior prevents the spread of pathogens that may be detrimental to a colony. To date, little is known about the ethological aspects of how termites deal with carcasses. Methodology and Principal Findings In this study, we tested the responses to carcasses of four species from different subterranean termite taxa: Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe) (lower termites) and Microcerotermes crassus Snyder and Globitermes sulphureus Haviland (higher termites). We also used different types of carcasses (freshly killed, 1-, 3-, and 7-day-old, and oven-killed carcasses) and mutilated nestmates to investigate whether the termites exhibited any behavioral responses that were specific to carcasses in certain conditions. Some behavioral responses were performed specifically on certain types of carcasses or mutilated termites. C. formosanus and R. speratus exhibited the following behaviors: (1) the frequency and time spent in antennating, grooming, and carcass removal of freshly killed, 1-day-old, and oven-killed carcasses were high, but these behaviors decreased as the carcasses aged; (2) the termites repeatedly crawled under the aging carcass piles; and (3) only newly dead termites were consumed as a food source. In contrast, M. crassus and G. sulphureus workers performed relatively few behavioral acts. Our results cast a new light on the previous notion that termites are necrophobic in nature. Conclusion We conclude that the behavioral response towards carcasses depends largely on the nature of the carcasses and termite species, and the response is more complex than was previously thought. Such behavioral responses likely are associated with the threat posed to the colony by the carcasses and the feeding habits and nesting ecology of a given species.

Developmental Stages and Castes of Two Sympatric Subterranean Termites Macrotermes gilvus and Macrotermes carbonarius (Blattodea: Termitidae)

ABSTRACT The developmental stages and castes of two sympatric subterranean termites, Macro-termes gilvus (Hagen) and Macrotermes carbonarius (Hagen) (Blattodea: Termitidae) were studied and biometric descriptors of each caste were developed for the identification of both species. Biometric descriptors revealed five well-defined groups of larval castes. After sex determination, three larval instars were detected in the development of minor and major worker castes. The first larval instars consist of both males and females which are homogenous in size. Size sexual dimorphism, in which females are smaller than males, occurs in the second larval instars, third larval instars, and worker castes. Minor and major soldiers are female sterile castes. Pictorial evidence of the fourth larval instar of M. carbonarius is presented herein; the individuals closely resemble minor workers but are poorly pigmented and have a distended abdomen, future presoldier-like mandibles, and a meso- and metanotum. In reproductive caste development, nymphs (derived from the first larval instars) undergo five moults from first to fifth instars before becoming winged termites.

Elimination of Field Colonies of a Mound-Building Termite Globitermes sulphureus (Isoptera: Termitidae) by Bistrifluron Bait

ABSTRACT The efficacy of Xterm, which contains 1% bistrifluron, in the form of cellulose bait pellets was evaluated for its efficacy in eradicating field colonies of the mound-building termite Globitermes sulphureus (Haviland) (Isoptera: Termitidae). The termite mounds were dissected at the end of the experiment to determine whether the colonies were eliminated. By ≈2 mo postbaiting, the body of termite workers appeared marble white, and mites were present on the body. The soldier—worker ratio increased drastically in the colonies, and the wall surface of the mounds started to erode. Colony elimination required at least a 4-mo baiting period. Mound dissection revealed wet carton materials (food store) that were greatly consumed and overgrown by fast-growing fungi. Decaying cadavers were scattered all over the nests. On average, 84.1 ± 16.4 g of bait matrix (68.9 ± 13.4%, an equivalent of 841 ± 164 mg of bistrifluron) was consumed in each colony. Moreover, we found that a mere 143 mg of bistrifluron was sufficient to eliminate a colony of G. sulphureus.

Toxicity and horizontal transfer of chlorantraniliprole against the Asian subterranean termite Coptotermes gestroi (Wasmann): effects of donor:recipient ratio, exposure duration and soil type.

BACKGROUND The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay. RESULTS The topical bioassay showed that chlorantraniliprole was significantly less active to C. gestroi at 24 h post-treatment compared with the other insecticides tested. Nevertheless, it is likely that a lesser amount of chlorantraniliprole was required to cause 50% mortality of C. gestroi at 7 and 14 days post-treatment. The exposure duration and donor:recipient ratio affect the mortality of recipient termites. Mortality after exposure to chlorantraniliprole in sandy clay was significantly lower than in sand; however, by 14 days, > 90% of donor and recipient termites died in both substrates, irrespective of concentration. Fipronil and imidacloprid showed faster action, and high to moderate toxicity to C. gestroi. Termite workers also ceased to feed after exposure for 1 h to 50 mg kg(-1) chlorantraniliprole-treated sandy clay. CONCLUSION Chlorantraniliprole demonstrated delayed toxicity at the lowest label rate (50 mg kg(-1) ) in sandy clay. Its slow action will enable greater transfer of toxicant between nestmates, while feeding cessation will promote greater social interaction between healthy and exposed termites.

Life Table of Paederus fuscipes (Coleoptera: Staphylinidae)

ABSTRACT The life history characteristics of the rove beetle Paederus fuscipes Curtis were studied under laboratory conditions using three field strains from Malaysia: Desa Wawasan (DW), Sri Pinang (SP), and Ampang Jajar (AJ). The total development time of immature stages differed significantly among the three strains, especially between DW (17.43 ± 0.16 d), SP (18.60 ± 0.19 d), and AJ (18.68 ± 0.22 d). Adult females and males from DW also exhibited a shorter life span, although the difference among strains was not significant. In terms of fecundity, the numbers of eggs laid per female for DW, SP, and AJ were 121.28 ± 15.98, 127.30 ± 18.01, and 147.45 ± 17.12, respectively. Additionally, because of the shorter life span in DW strain, two apparent peaks in age-stage specific fecundity were detected. The beetles compensated for their shorter life span by increasing their reproductive activity to sustain the progeny in the population. The intrinsic rates of increase (r) of P. fuscipes from DW, SP, and AJ were 0.0773 ± 0.0046 d-1 0.0788 ± 0.0051 d-1, and 0.0873 ± 0.0054 d-1, respectively; and the net reproduction rates (R 0) were 40.09 ± 7.39 offspring, 45.29 ± 8.74 offspring, and 42.34 ± 8.25 offspring, respectively. The mean generation time of P. fuscipes from AJ was 43.08 ± 1.07 d, which was significantly higher than that from DW (47.95 ± 1.36 d) and SP (48.57 ± 1.43 d). The total immature development time of P. fuscipes in this study was shorter than values reported in previous studies.

Flight activity of two sympatric termite species, Macrotermes gilvus and Macrotermes carbonarius (Termitidae: Macrotermitinae).

ABSTRACT Flight activities of two sympatric termite species, Macrotermes gilvus (Hagen) and Macrotermes carbonarius (Hagen), were studied in Penang Island, Malaysia. Herein, we present the first documentation of chronological reproductive isolation of M. gilvus and M. carbonarius. Flights of M. gilvus were recorded over a remarkably long 7-mo period from March to September, whereas swarming of M. carbonarius took place from November to January. Swarming events of M. gilvus and M. carbonarius occurred under atmospheric pressures of 1,005–1,011 and 1,006–1,010 hPa, respectively. Most flights of M. gilvus occurred on days with rain, whereas M. carbonarius avoided rain. Flight activity of M. gilvus was correlated significantly with atmospheric pressure and rainfall. The threshold temperature and relative humidity of M. gilvus flights were between 23 and 26°C and 83 and 98% RH, respectively; M. carbonarius swarmed between 25 and 30°C and 72 and 83% RH, respectively. The flight activity of M. gilvus concentrated in the warmer and humid months with a monthly total rainfall of 228 mm. Both species swarmed at distinct times of day during the limited field observations: Flights of M. gilvus began between 0300 and 0430 hours (light intensity <1 Lx), and flights of M. carbonarius lasted for only 4–10 min between 1900 and 1910 hours (at dusk; light intensity: 20–200 Lx). Windless conditions were preferred for the flights of both species.

Influence of Temperature on Survival and Water Relations of Paederus fuscipes (Coleoptera: Staphylinidae)

ABSTRACT The effects of four temperatures (15, 23.5, 28, and 35°C) on the biological characteristics of the rove beetle Paederus fuscipes Curtis were studied, and its cuticular permeability also was measured. Specimens successfully developed to adulthood at each temperature tested, but development time of each preadult stage significantly decreased with increasing temperature. Both egg and L1 stages required at least 80 degree days above a threshold of ≈10°C to develop to the subsequent stage. The lengthy development time and high survival rate of preadults at 15°C suggests that P. fuscipes can survive in a harsh environment during cold weather by hibernating, and this ability could allow preadults to succeed ecologically in temperate countries. However, adult longevity was short, and no fecundity was recorded at 15°C. At 28°C, P. fuscipes exhibited a high survival rate of adults, which had a longer life span and high fecundity; thus, the population had the highest intrinsic rate of increase (0.0788 ± 0.0051 d-1) and the shortest mean generation time (48.57 ± 1.43 d) at 28°C. At this temperature, the population might reach a size that could facilitate invasion into residential areas. However, in the absence of a hygric environment, P. fuscipes was unable to survive despite favorable temperature. Unlike in adults and pupae, high cuticular permeability values were found in the larval stages. This indicates that larvae are highly susceptible to desiccation, and it explains why the distribution of P. fuscipes is restricted to moist habitats.

Dispersal Pattern of Paederus fuscipes (Coleoptera: Staphylinidae: Paederinae) in Relation to Environmental Factors and the Annual Rice Crop Cycle

ABSTRACT Paederus fuscipes Curtis, a dermatitis linearis causing agent, has received increasing attention from the public, as it poses a serious health threat after mass dispersal into human-dominated areas. Preventive measures against this insect have so far been unsuccessful partly because of limited knowledge about its dispersal pattern. In this study, the dispersal activity of P. fuscipes was studied at infestation-prone residential buildings in Mainland Penang, Malaysia. The dispersal activity of P. fuscipes showed two peaks, that is, from February to April and August to October. Overall, there was no statistical significant correlation between dispersal and climatic parameters, that is, temperature, relative humidity, total rainfall, at all sampling localities. However, dispersal was primarily caused by human activities in rice fields, which accounted for >60% of the variability in dispersal. Particularly, rice harvesting, including straw burning, and cultivation were the major factors triggering P. fuscipes dispersal. These activities presumably disrupted the habitat and normal activities of P. fuscipes and rendered the rice fields unfavorable refuges. In addition, the beetles might also face food shortages after the disturbance of their prey base in the crop fields. The current study provides a predictive tool of P. fuscipes flight periods to ensure insecticide residual spraying is timed in the infestation-prone residential areas before the onset of infestation.

Subterranean termite open-air foraging and tolerance to desiccation: Comparative water relation of two sympatric Macrotermes spp. (Blattodea: Termitidae) ☆

The foraging patterns of termites are strongly related to physiological limits in overcoming desiccation stress. In this study, we examined moisture preferences and physiological characteristics of Macrotermes carbonarius (Hagen) and M. gilvus (Hagen) as both exhibit conspicuous patterns of foraging activity. Despite both species showing no significant differences in calculated cuticular permeability, and percentage of total body water, they differed greatly in rate of water loss and surface area to volume ratio. For example, M. carbonarius which had a lower surface area to volume ratio (29.26-53.66) showed lower rate of water loss and percentage of total body water loss. This also resulted in higher LT(50) when exposed to extreme conditions (≈2% RH). However, contrasting observations were made in M. gilvus that has smaller size with higher surface area to volume ratio of 40.28-69.75. It is likely that the standard equation for calculating insect surface areas is inadequate for these termite species. The trend was further supported by the result of a moisture preference bioassay that indicated M. carbonarius had a broader range of moisture preference (between 5% and 20%) than M. gilvus which had a relatively narrow moisture preference (only 20%). These results explain why M. carbonarius can tolerate desiccation stress for a longer period foraging above-ground in the open air; while M. gilvus only forages below ground or concealed within foraging mud tubes.

Colony Size Affects the Efficacy of Bait Containing Chlorfluazuron against the Fungus-Growing Termite Macrotermes gilvus (Blattodea: Termitidae)

ABSTRACT The efficacy of chitin synthesis inhibitors (CSIs) against fungus-growing termites is known to vary. In this study, 0.1% chlorfluazuron (CFZ) cellulose bait was tested against medium and large field colonies of Macrotermes gilvus (Hagen). The termite mounds were dissected to determine the health of the colony. Individual termites (i.e., workers and larvae) and fungus combs were subjected to gas chromatography-mass spectrometry (GC—MS) analysis to detect the presence of CFZ. In this study, 540.0 ± 25.8 g (or equivalent to 540.0 ± 25.8 mg active ingredient) and 680.0 ± 49.0 g (680.0 ± 49.0 mg active ingredient) of bait matrix were removed by the medium- and large-sized colonies, respectively, after baiting. All treated medium-sized colonies were moribund. The dead termites were scattered in the mound, larvae were absent, population size had decreased by 90%, and the queens appeared unhealthy. In contrast, no or limited effects were found in large-sized colonies. Only trace amounts of CFZ were detected in workers, larvae, and fungus combs, and the population of large-sized colonies had declined by only up to 40%. This might be owing to the presence of large amount of basidiomycete fungus and a drastic decrease of CFZ content per unit fungus comb (a main food source of larvae) in the large-sized colonies, and hence reduced the toxic effect and longer time is required to accumulate the lethal dose in larvae. Nevertheless, we do not deny the possibility of CSI bait eliminating or suppressing the higher termite if the test colonies could pick up adequate lethal dose by installing more bait stations and prolonging the baiting period.