Does Manipulation by the Parasitoid Wasp Cotesia glomerata (L.) Cause Attachment Behaviour of Host Caterpillars on Cocoon Clusters?

Some parasitoid wasps appear to control the behaviour of their hosts. However, altered behaviours of parasitised hosts are not necessarily caused by parasitoids but are sometimes the result of traumatic side effects of parasitism. However, it was difficult for us to discriminate the cause of host's behaviours between manipulation by parasitoids and traumatic side effects. Larvae of the parasitoid wasp Cotesia glomerata form cocoon clusters after egression from the parasitised host caterpillar Pieris brassicae . Following parasitoid egression, host caterpillars survive for several days and remain near the cocoon clusters. These caterpillars may repel solitary pteromalid hyperparasitoid wasps, Trichomalopsis apanteloctena , that attempt to parasitise fresh C. glomerata pupae. We allowed hyperparasitoids to attack cocoon clusters in the field and laboratory and then assessed the costs and benefits to C. glomerata of attachment by the parasitised caterpillars. The eclosion success of C. glomerata in cocoon clusters with attached caterpillars was higher than that in clusters without attached caterpillars in both field and laboratory experiments. This difference was attributed to shorter hyperparasitoid visits to cocoon clusters with attached host caterpillars. However, large cluster size was potentially costly for host attachment, because the duration of host caterpillar attachment decreased with increasing numbers of C. glomerata per caterpillar. This trade-off may be related to shortages of fat body resources, which are shared between the development of wasp larvae and the survival of host caterpillars. Therefore, we concluded that caterpillar attachment satisfied some requirements of host manipulation by C. glomerata .     

Effect of humidity on the development and fecundity of <Emphasis Type="Italic">Ophraella communa</Emphasis> (Coleoptera: Chrysomelidae)

Ophraella communa, an unintentionally introduced leaf beetle in China, has good control efficiency on ragweed, Ambrosia artemisiifolia. Aspects of the climatic requirements for development, survival, longevity and fecundity of O. communa were studied under the conditions of constant temperature (25 ± 1°C), photoperiod of 14 L:10 D and three relative humidities (60%, 75% and 90% RHs). The results showed that the developmental periods of O. communa at different stages shortened along with the increasing relative humidity, except that of the pupal stage. Although no differences were observed in the pupal survival rate, ovipositional period, fecundity, longevity and adult female age-specific survivorship of O. communa under the three humidity conditions, the survival rates during the egg, larva and entire immature stage were significantly higher at 75% RH and 90% RH than at 60% RH. The innate rate of increase (r _m), net reproductive rate (R ₀), finite rate of increase (λ) reached the maximum at 75% RH, with values of 0.181, 1116.4 and 1.198, respectively. These results indicated that the optimum relative humidity for the development of O. communa ranged from 75% RH to 90% RH. Thus O. communa prefers moist microclimate habitats. Its population may expand rapidly during mid-May to late August in south, east and central China, when the humidity is relatively high.     

Remarkable similarity in body mass of a secondary hyperparasitoid Lysibia nana and its primary parasitoid host Cotesia glomerata emerging from cocoons of comparable size

Lysibia nana is a solitary, secondary idiobiont hyperparasitoid that attacks newly cocooned pre-pupae and pupae of several closely related gregarious endoparasitoids in the genus Cotesia, including C. glomerata. Prior to oviposition, the female wasp injects paralysing venom into the host, thus preventing further development. Here, host fate, emerging hyperparasitoid mass, and egg-to-adult development time was compared in hosts parasitized at different ages over 24-h intervals. Cocoons of C. glomerata were parasitized by L. nana at 12, 36, 60, 84, and 108 h post-egression from the secondary host, Pieris brassicae. Hyperparasitoid survival exceeded 80% in hosts parasitized within the first 60 h after pupation, but dropped thereafter, with no hyperparasitoids emerging in hosts aged 108 h. The mass of hyperparasitoids was positively correlated with the mass of the host cocoon, and this relationship remained consistent in hosts up to 60 h old. Within each host age cohort, the mass of male and female wasps was not significantly different. Development time in L. nana was uniform in hosts up to 60 h old, but increased significantly in 84-h-old hosts, and male wasps completed their development earlier than female wasps. Regulation of host growth varied with the age of the host at parasitism, with the early growth of older hosts reduced much more dramatically than young hosts. Unlike most parasitoids, pupal hyperparasitoids do not make cocoons but instead pupate within the already prepared cocoon of the host parasitoid. Consequently, for a given mass of cocoon, newly emerged L. nana adults were remarkably similar in size with male and female adults of C. glomerata. This reveals that L. nana is extremely efficient at exploiting its primary parasitoid host.     

Effect of relative humidity on development, survival and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae)

The effect of five constant relative humidity (RH) regimes (12%, 33%, 55%, 75% and 94%) on the preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister was studied at 26 ± 1 °C and a photoperiod of 16:8 (L:D) under laboratory conditions. For the experiments, larvae were fed individually on eggs of the flour moth Ephestia kuehniella (Zeller), whereas adults on a liquid diet consisting of water, yeast hydrolysate, sugar and honey. The experimental insects were maintained individually in sealed plastic containers with saturated water salt solutions at the base to control RH. Preimaginal developmental time from egg to adult for females and males was significantly shorter at 75% and 94% RHs than at other RHs in the range from 12% to 55%. Percentages of adult emergence were similar at all RHs tested and varied from 52.5% to 75.0%. Adult females that had no access to water and were maintained at 12%–75% RH lived on average less than two weeks and laid no eggs, whereas at 94% RH they lived longer and each laid on average 201 eggs. When the females had periodic access to a water source a significant increase in both longevity and egg production occurred and the estimated intrinsic rate of increase was high, irrespective of RH. These results could be useful for the mass-rearing of D. prasina and for better understanding its population dynamics under field conditions.     

Life-history traits in closely related secondary parasitoids sharing the same primary parasitoid host: evolutionary opportunities and constraints

Thus far, few studies have compared life-history traits amongst secondary parasitoids attacking and developing in cocoons of their primary parasitoid hosts. This study examines development and reproduction in Lysibia nana Gravenhorst and Acrolyta nens Hartig (both Hymenoptera: Ichneumonidae), two related and morphologically similar secondary parasitoids that attack pupae of the gregarious endoparasitoid, Cotesia glomerata L. (Hymenoptera: Braconidae). On black mustard, Brassica nigra L. (Brassicaceae) plants in a field plot, adults of L. nana and A. nens frequently emerged from the same cocoon broods of C. glomerata . Based on similarities in their phylogeny and morphology, it was hypothesized that both species would exhibit considerable overlap in other life-history traits. In both L. nana and A. nens , adult wasp size increased with host cocoon mass at parasitism, although L. nana wasps were slightly larger than A. nens wasps, and completed their development earlier. Adult females of both species emerged with no eggs but matured eggs at similar rates over the following days. When provided with 20 host cocoons daily, fecundity in female L. nana was slightly more skewed towards early life than in A. nens , although lifetime fecundity did not differ between the two species. Longevity was significantly reduced in females of both species that were provided with hosts. Both parasitoids were found to exhibit strong similarities in life-history and development traits and in their ecological niche, thereby supporting our general hypothesis. Competition between L. nana and A. nens is presumably diffused because their preferred host ( C. glomerata ) is relatively abundant in open habitats.     

Behavioral manipulation of host caterpillars by the primary parasitoid wasp Cotesia glomerata (L.) to construct defensive webs against hyperparasitism

Many parasitoids control the behavior of their hosts to achieve more preferable conditions. Decreasing predation pressure is a main aim of host manipulation. Some parasitoids control host behavior to escape from their enemies, whereas others manipulate hosts into constructing defensive structures as barriers against hyperparasitism. Larvae of the parasitoid wasp Cotesia glomerata form cocoon clusters after egression from the parasitized host caterpillar of the butterfly Pieris brassicae. After the egression of parasitoids, the perforated host caterpillar lives for a short period and constructs a silk web that covers the cocoon cluster. We examined whether these silk webs protect C. glomerata cocoons against the hyperparasitoid wasp Trichomalopsis apanteroctena. In cocoon clusters that were not covered by silk webs (bare clusters), only cocoons hidden beneath others avoided hyperparasitism. In covered cocoon clusters, both cocoons hidden beneath others and those with a space between them and the silk web avoided hyperparasitism, whereas cocoons that contacted the silk webs were parasitized. The frequency of cocoons that were hidden beneath others increased with the increasing number of cocoons in a cluster, but the defensive effect of cluster size was thought to be lower than that of silk webs. However, the rate of hyperparasitism did not differ between covered and bare clusters when we allowed the hyperparasitoids to attack the cocoon clusters in an experimental arena. This result was thought to have been caused by low oviposition frequency by these hyperparasitoids. As a result, silk webs did not guard the cocoons from hyperparasitoids in our experiments, but would protect cocoons under high hyperparasitism pressure by forming a space through which the ovipositors could not reach the cocoons.     

STUDIES ON BIONOMICS OF LIPOSCELIS ENTOMOPHILA (PSOCOPTERA:LIPOSCELIDIDAE) INFESTING STORED PRODUCTS*

Abstract This paper deals with the biological characteristics of the psocid Liposcelis entomophila (Enderlein) on a diet composed of whole wheat flour and yeast (10: 1) under different temperatures (17.5–35C) and relative humidities (50%-90% RH). The results showed that at 75% RH development time from egg to adult varied from 71. 9 d at 20% to 21.7 d at 35C. At 28C it varied from 23.0 d at 90% RH to 34.4 d at 60% RH. The development threshold and the effective accumulated temperature for entire immature stages were estimated at 15. 7C and 460. 7 day-degree, respectively. The survival rate from egg to adult was 64. 5% at 27. 5C while at 20C and 35C it was only 32.1% and 37. 0%, respectively. At 28C the survival rate ranged from 31. 2% at 60% RH to 67.8% at 80% RH. L. entomophila could not survive at any humidity at 17. 5C and below 50% RH. The average longevity of adult ranged from 32.4 d at 35C and 64.4 d at 20C. At 75% RH the mean egg production varied from 27.1 at 27. 5 C and 13. 9 at 20C and the greatest fecundity occurred at 90% RH with 28C. The optimal ranges of temperature and humidity for L. entomophila population growth were 27. 5–30C and 80%—90% RH. The distribution and the reason for its serious infestation in China are discussed.     

Temporal organization of chilling resistance in cotton seedlings: effects of low temperature and relative humidity

The effect of temperature and relative humidity (RH) on the time course of the rhythmic endogenous changes of chilling resistance was studied in cotton (Gossypium hirsutum L. cv. Deltapine 50) seedlings grown under light-dark cycles of 12:12 h. The resistant phase to 5° C, 85% RH lasted during most of the dark period while to 5° C, 100% RH it was longer and extended into the last half of the light period because a transient phase advance occurred when chilling started at the middle of the light period. Seedlings acclimated by low temperature were resistant throughout the light-dark cycle. A treatment with 100% RH before chilling to acclimated seedlings introduced a sensitive phase that corresponded to that of non-acclimated seedlings. In non-acclimated seedlings, this treatment decreased the resistance but the basic pattern of the rhythm was sustained. Changes in chilling resistance were analyzed under fluctuating temperatures and RHs, and explained taking into consideration the functioning of the circadian clock and environmental induction of resistance.Abbreviations CR chilling resistance - LDC light-dark cycle of 24 h - RH relative humidity     

The adaptive value of hatching towards the end of the night: lessons from eggs of the haematophagous bug Rhodnius prolixus

Abstract. The daily hatching rhythm of Rhodnius prolixus eggs is established under an LD 12 : 12 h photoperiod. The endogenous nature of this rhythm is demonstrated under continuous darkness. Hatching takes place during the last half of the night, when the maximum environmental relative humidity (RH) and minimum temperature (i.e. the combination that yields the lower water vapour saturation deficits) occur in wild habitats. This temporal window of approximately 7 h recurs at 24‐h intervals, producing a hatching rhythm in the population. The effects of the RH upon egg‐hatching are analysed. In agreement with previous studies, hatching success is strongly affected by environmental RH. Although 88% of eggs hatch at 75% RH, only 4% and 10% hatch at 0% or 100% RH, respectively. These results support the hypothesis that temporal synchronization is related to the avoidance of low environmental RHs, high environmental temperatures, or high water vapour saturation deficit during hatching, thus minimizing their deleterious effects. Given that eggs cannot choose optimum microclimatic conditions, selective pressures appear to have originated from an adaptive temporal rather than spatial hygropreference.     

Influence of Temperature and Relative Humidity on Germinability of Mucor piriformis Spores

Studies were conducted to determine the influence of temperature and relative humidity (RH) on germinability and viability of Mucor piriformis spores. Spores did not survive when stored at 35 °C and their survival rate decreased rapidly at 30 °C; however, spores remained viable for more than 1 year at 0 °C. RH also significantly affected spore viability. Spores held at 26 °C and 100% RH no longer germinated after 35 days, while those held at 75 or 90% RH germinated for 65 days. At 20 °C, RH had little effect on spore germinability. The effect of temperature and RH on percentage spore germination also varied. At all temperatures studied, spore viability decreased more rapidly with time at 100% RH than at 75 or 90% RH. The least favorable, temperature-humidity combination, 30 °C and 100% RH, decreased spore germination from 100% to less than 1% in 14 days.     

Cold tolerance of coccons ofAllorhogas pyralophagus [Hym.: Braconidae]

Cold tolerance studies were conducted under laboratory conditions for coccons ofAllorhogas pyralophagus Marsh, a Mexican parasitoid of graminaceous borers. By storage, developmental time (from cocoon to adult emergence) could be extended by 2 to 6 times. However, cocoons stored for more than 14 days at 2°C failed to survive, while at 5 and 10°C, about 50% emergence was recorded for upto 21 days of storage. With respect to survival and adult longevity, 10°C seemed to be the most suitable storage temperature. Pre-emergence period was also significantly increased by storing cocoons for 21 to 35 days at this temperature. Sex-ratio of emerging adults was not significantly affected by storage. Fecundity was adversely affected in all the treatments except in the case of females emerging from cocoons stored at 5°C for 7 days. The progeny of parasitoids which emerged from cocoons stored at 5 and 10°C for 35 days consisted of only males. It is clear from the present study thatA. pyralophagus cocoons are more amenable to short-term storage. Contribution No. 285/87 of the Indian Institute of Horticultural Research, Bangalore-560 089.     

Effect of temperature and relative humidity on spinning behaviour of silkworm (Bombyx mori.L)

The rate of spinning of silkworm larva (Bombyx mori.L) was slow at 22 degrees C and fast at 38 degrees C. The time taken for completion of cocoon was longest at 98 +/- 2% and least at 40 +/- 2% RH. However, good quality cocoons were spun at 22 degrees C and 65 +/- 5% RH, hence it would be advantageous to maintain this temperature and relative humidity at the time of cocoon spinning in the case of CB race of silkworm.     

脱水速率和降温速率对葡萄柚种子超低温保存的影响

以新鲜葡萄柚(Citrus paradise)种子为材料,使用3种脱水速率处理至约20%含水量,然后用饱和盐溶液平衡至10种不同的含水量,再进行简化的二步法超低温保存;同时,以经过15 ℃、50%相对湿度(RH)条件脱水至含水量约12%的葡萄柚种子为材料,使用程序降温仪进行5个降温速率和3个预冷温度的传统二步法超低温保存。结果表明,葡萄柚种子对脱水敏感,种子含水量越低,成苗率越低。而且,脱水速率越快,对种子的损伤越大,成苗率呈现75% RH>50% RH>15% RH;冷冻处理对种子有进一步的伤害,含水量6%～8%的种子超低温保存效果最佳,但脱水速率对超低温保存的种子成苗率的影响不明显。用传统二步法超低温保存葡萄柚种子,与预冷对照相比,经液氮冷冻的种子成苗率都有明显下降。在预冷对照组中,-2.5 ℃·min^-1降温速率的种子成苗率最高,在冷冻保存中-0.5 ℃·min^-1和-0.25 ℃·min^-1的降温速率最有利于超低温保存。预冷温度从-40 ℃降至-60 ℃,未超低温处理种子的发芽率降低,但超低温处理种子的发芽率提高。     

The parasitoid wasp Eruga unilabiana Pádua & Sobczak,sp. nov. (Hymenoptera: Ichneumonidae) induces behavioral modification in its spider host

Some polysphinctine parasitoid wasps can alter the web building behavior of their host spiders. In this paper, we describe and illustrate a new species Eruga unilabiana sp. nov. and report for the first time, to the best of our knowledge, the interaction between this parasitic wasp and the linyphiid spider Dubiaranea sp. We investigated the wasp's host selection, development, and manipulation of host behavior. We found that most of the parasitized spiders were intermediate‐sized adult females that probably provide sufficient resources for parasitoid larvae and are less vulnerable for parasitoid females than larger host individuals at attack. The cocoon web of Dubiaranea sp. consists of a complex three‐dimensional tangle structure with several non‐stick radial lines that converge at the cocoon. In addition, E. unilabiana individuals construct their cocoons horizontally, which differ from cocoons of the majority of polysphinctine wasps. This study provides important information and discussion to further understand the evolution of parasitoid wasp–spider interactions.     

湿度对木薯单爪螨Mononchellus mcgregori发育与繁殖的影响

【目的】木薯单爪螨是新入侵我国的重要检疫性害螨,主要危害木薯,也可危害橡胶。近年来,该螨种群数量迅速增多,扩散范围不断增大,目前已在海南、云南、广西、广东等重要木薯产区发生并加重危害,危害严重时可导致木薯减产40%~60%。湿度是影响木薯单爪螨发育和繁殖的重要因素之一,但有关该方面的研究较少。【方法】通过室内饲养,观察比较了不同湿度条件下木薯单爪螨发育及繁殖情况。【结果】当湿度为75%和85%时,卵孵化率均达100%,平均每雌产卵量分别达49.22和43.67粒,雌成螨寿命分别为21.00和22.00 d;当湿度为55%和95%时,卵孵化率和后代产卵量显著降低,雌成螨寿命显著缩短;当湿度为65%时,卵孵化率、平均每雌产卵量以及成螨寿命均与75%和85%湿度处理无显著差异,但其发育历期显著延长。【结论】75%和85%是木薯单爪螨发育与繁殖的适宜湿度条件。     

Biological assessment of Tetrastichus brontispae,a pupal parasitoid of coconut leaf beetle Brontispa longissima

To control coconut leaf beetle, Brontispa longissima (Gestro), the pupal parasitoid Tetrastichus brontispae Ferrière was imported from Taiwan and its biology was studied in quarantine in Hainan, China. The parasitoid development includes an egg, three larval instars and three pupal stages. Its developmental time from egg to adult was 19.5±0.5 days under conditions of 24±2°C and 75±5% relative humidity (RH). Temperature had no effect on the sex ratio of offspring, but significantly affected the parasitism rate and reproduction. The parasitism rates were 98.07, 97.97 and 95.03% at 28, 24 and 20°C, respectively, whereas the parasitism rate was 52.18% at 18°C and 69.48% at 30°C, respectively. Furthermore, the parasitoids reared at 18 and 30°C produced fewer offspring than those at 20, 24 and 28°C, respectively. With the increase in temperature, developmental time decreased linearly from 46.19 days at 18°C to 17.10 days at 28°C. RH significantly influenced development, parasitism rate and the reproduction of T. brontispa. With the decrease of RH, developmental time increased from 22.94 days at 20% RH to 18.84 days at 95% RH. In contrast, parasitism rate and the number of offspring per female increased with the increase of RH. Though emergence rates between 50 and 95% RH were much higher than those between 20 and 35% RH, the sex ratios between 20 and 95% RH were not different. Photoperiod had no effect on parasitism, the number of offspring per female, emergence and the sex ratio of T. brontispae, but developmental time was significantly different for different photoperiods. Sucrose, honey and glucose significantly enhanced adult longevity, parasitism and the number of offspring per female of T. brontispae, but had no effect on the sex ratio and survival. Females of T. brontispae only parasitized fourth to fifth larval instars and 1–5-day-old pupae, but there was a significant difference in the number of offspring per female, development time, emergence and the sex ratio of offspring in different instars. These results showed that 1-day-old pupae, a temperature of 24–28°C and 65–95% RH were optimal for T. brontispae. These findings should be helpful in developing a production system to rear and release T. brontispae in large enough quantities to effectively control coconut leaf beetle.     

Water balance and humidity requirements of house dust mites

The house dust mites,Dermatophagoides farinae, D. pteronyssinus andEuroglyphus maynei, are prevalent in homes in humid geographical areas throughout the world. These mites thrive in humid environments in human dwellings where there is no liquid water to drink. However, their bodies contain 70–75% water by weight, which must be maintained in order to reproduce. Their primary source of water is water vapor which is actively extracted from unsaturated air. At relative humidities above 65–70%, adequate amounts of water can be extracted from unsaturated air to compensate for that lost by all avenues. Active uptake is associated with ingestion of a hyperosmotic solution which is secreted by the supracoxal glands. Active mites do not survive longer than 6–11 days at RHs 50%. They survive extended dry periods by forming a desiccation-resistant protonymphal stage which can survive for months at RHs below the critical humidity for active stages. Feeding rate and allergen production is directly influenced by RH. Mites feed, multiply, and produce more fecal matter at higher RHs than at lower ones.     

Photosynthetic response to dynamic changes of light and air humidity in two moss species from the Tibetan Plateau

Bryophytes are widely distributed in alpine meadow and wetlands on the Tibetan Plateau, where light intensity and air moisture are highly variable in time. To address how bryophytes respond to their light and moisture environments, we examined dynamic photosynthesis in two moss species, Distichium inclinatum common in meadow, and Encalypta alpine frequently found in wetland. Photosynthetic induction response was faster in the two moss species than in most vascular species. In both species the 90% induction time after a sudden light increase from 50 to 600 μmol m⁻² s⁻¹ was within 3 min. The induction was faster in mosses experiencing a period of weak light than in those in total darkness. E. alpina, the wetland species, showed more rapid induction response and shorter post-illumination CO₂ fixation to sunflecks than D. inclinatum, the meadow species. Photosynthetic rate (A _max) under saturated light in the two species increased linearly with increasing air relative humidity (RH). The meadow species D. inclinatum showed higher A _max under low RHs, but exhibited lower A _max under high RHs in comparison with the wetland moss E. alpina. Moreover, the quantum efficiency increased linearly with increasing RH, indicating that air humidity plays a critical role in photochemical activities in the alpine mosses. The study suggests that there are acclimations in dynamic photosynthesis in response to light and humidity, and the acclimations would benefit a high leaf carbon gain in the two alpine moss species in their common habitats.     

Effects of temperature and humidity on emergence dynamics of Plutella xylostella (Lepidoptera: Plutellidae)

The effects of temperature and humidity on the emergence patterns of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were studied at four temperatures (20, 25, 28, and 33 degrees C),three relative humidities (50, 70, and 90%) and a photoperiod of 14:10 (L:D) h. Both sexes emerged primarily in the late afternoon to early morning, and the peaks of emergence varied depending on temperature and humidity. Females emerged significantly earlier than males. Incubation at 33 degrees C and 90% RH had a significant effect on the emergence rate, but no significant interaction was found between temperature and humidity. Emergence duration was 25.3 h for both sexes at 90% RH, with emergence duration at 33 degrees C lower than the other treatments. The sex ratios of diamondback moth under different temperature and humidity treatments were approximately 1:1, and there were no significant effects of temperature and humidity or interactions between these two factors.     

Reproduction of Lumbricillus rivalis (Levinsen) in laboratory cultures and in decaying seaweed

The cocoon production of 144 Lumbricillus rivalis cultured in pairs at 10 ± 1 °C was high over the first 2 weeks of breeding activity and then declined, chiefly because of high mortality. Cocoon deposition lasted for between 1 and 16 weeks, eight pairs of worms producing cocoons for 9 weeks and one pair for 16 weeks. During the total period of cocoon deposition over 9000 eggs (mean 17·4 per cocoon) were deposited. Two decaying wrack bed populations of L. rivalis showed a low level of cocoon and egg production in autumn, rising to an annual maximum in late winter/early spring. In these populations the mean egg content varied seasonally from 17·1 to 47·8 eggs per cocoon. When cocoons in the laboratory were transferred from the site of deposition to incubation dishes 31% hatched, but those left in the substrate showed a 92% hatch. In the naturally occurring populations 19% of the cocoons detached from seaweed fronds hatched, but 62% of those left in situ. Eggs and worm embryos developed to relatively late stages in most cocoons, whatever the rate of hatching; development often continued for up to 2 months after deposition without hatching. Over 50% of the fertile eggs in cocoons from decaying wrack hatched and developed to 5 mm worms.