Development and parasitism of Lysiphlebus testaceipes (Cresson) and Aphidius colemani Viereck (Hymenoptera: Braconidae) on Aphis gossypii Glover (Hemiptera: Aphididae) on two chrysanthemum cultivars

The parasitoids Lysiphlebus testaceipes (Cresson) and Aphidius colemani Viereck play an important role on the regulation of aphid populations on chrysanthemum grown in greenhouses. This study evaluated the interaction of biological control and plant resistance by the development and the parasitism of L. testaceipes and A. colemani on Aphis gossypii Glover. The aphid host was kept on commercial cultivars of chrysanthemum susceptible Yellow Snowdon (YS) and resistant White Reagan (WR). The experiment was carried out in climatic chamber at 22 +/- 1 masculineC, 70 +/- 10% RH, and photophase 12h. Nymphs of 2nd and 3rd instars of A. gossypii attacked only once by the parasitoids were used in the experiment. The development time was 15.0 and 12.9 days for L. testaceipes and 17.0 and 16.3 days for A. colemani kept on A gossypii on cvs. YS and WR, respectively. The parasitoid L. testaceipes showed greater parasitism rate (68.4%) on A. gossypii on cv. YS than on WR (50%), and for A. colemani was not found significative difference on parasitism (46.8 and 35% to YS and WR, respectively). The emergence rates of L. testaceipes and A. colemani were 91.6% and 85.3% on A gossypii reared on YS, and 78.1% and 100% on WR, respectively. The longevity of A colemani and the parasitism rate of L. testaceipes were affected in a negative way by the cv. WR. The results indicated a positive interaction of biological control with parasitoids and the resistant cv. WR on A. gossypii control in protected cultivation.     

Fertility life table of Aphidius colemani Viereck (Hymenoptera: Braconidae, Aphidiinae) on Aphis gossypii Glover (Hemiptera: Aphididae)

The intrinsic rate of increase of a parasitoid related to its hosts play an important role in biological control programs. In this work, fertility of the parasitoid Aphidius colemani Viereck was evaluated on Aphis gossypii Glover by means of a fertility life table. To determine the immature mortality, the development time and the sex ratio, 12 mated females of A. colemani (24h old), and 240 nymphs of A. gossypii (3 days old) were used. To evaluate fertility 15 mated females (24h old) were used. For each parasitoid female, 300 nymphs were offered in the 1st day, 250 nymphs in the 2nd day, 200 nymphs in the 3rd day, 150 nymphs in the 4th day, 100 nymphs in the 5th day and 50 nymphs in the other days. Immature mortality of A. colemani was 22.1%, development time of males and females were 12.0 and 11.8 days, respectively, and sex ratio was 0.6. The females of A. colemani laid 420 eggs and had longevity of 5.9 days. The net reproduction rate (R(o)) was 194.81 females and the intrinsic rate of increase (r(m)) was 0.384 females/females/day. The finite rate of increase (lambda) was 1.48 females/day, the mean length of a generation (T) was 13.74 days and the time to duplication the population (TD) was 12.60 days. The parasitoid A. colemani had a great potential of population growth on A. gossypii as a host and could be an effective biological control agent of this aphid.     

Host instar and host plant effects on Aphidius colemani

Abstract:  The effect of Myzus persicae age (I–IV instar nymphs) on parasitism by Aphidus colemani was investigated in choice experiments with either aubergine ( Solanum melongena L.) or pepper ( Capsicum annuum L.) as the aphid host plant species. Aphidius colemani could develop successfully to the mummy stage in all ages of aphid tested, on both pepper and aubergine plants. The greatest proportion of parasitoid mummies was found with II and III aphid instars on pepper and on I, II and III aphid instars on aubergine. On aubergine, I instar nymphs were also parasitized to an appreciable degree. Successful parasitism of IV instar nymphs was consistently low on both crops. The potential implications of host plant effects on the effectiveness of A. colemani as a biological control agent are discussed.     

Influence of host size variation on the development of a koinobiont aphid parasitoid, Lysiphlebus ambiguus Haliday (Braconidae, Hymenoptera)

To determine whether host body size is the currency used by the aphidiine parasitoid, Lysiphlebus ambiguus Haliday (Hymenoptera: Braconidae), in assessing host quality, the aphid, Aphis fabae Scopoli (Homoptera: Aphididae), was reared at either high or low temperature to yield hosts of the same instar with different body sizes. Cohorts of A. fabae raised at 15 degrees C and 30 degrees C and exposed to individual female L. ambiguus in no-choice tests were successfully parasitized in all host stages from 1st instar nymphs to adults. However, younger and smaller aphids were more susceptible to parasitism than older and larger nymphs or adults, as measured by the number of mummies produced. For aphid cohorts reared at 15 degrees C, the proportion of female progeny, progeny adult size, and development time all increased linearly with aphid size at the time of attack. In contrast, for aphid cohorts raised at 30 degrees C, the proportion of female progeny and progeny adult size declined with aphid size, while development time remained unaffected. Through manipulation of host rearing temperature, we have shown that at cooler temperatures the koinobiont parasitoid, L. ambiguus, responds to host size in the same way as an idiobiont parasitoid, but that this response is compromised at higher temperatures. Our results suggest that differential mortality during development is likely to influence the observed secondary sex ratio in relation to aphid size for aphid cohorts raised at higher temperatures due to disruption of the activity of the host's primary endosymbiont and that such reduced nutritional quality of aphids cannot be compensated by increased development time.     

Life table of Tamarixia radiata (Hymenoptera: Eulophidae) on Diaphorina citri (Hemiptera: Psyllidae) at different temperatures

Tamarixia radiata (Waterston, 1922) is the main parasitoid of Diaphorina citri (Kuwayama, 1907), and has been used in classical biological control programs in several countries. The current study investigated the biology and determined the fertility life table of T. radiata in different temperatures, to obtain information to support the establishment of a biological control program for D. citri in Brazil. Fifth-instar nymphs of D. citri were offered to females of T. radiata for parasitism, for 24 h. Then, the parasitoid was removed and the nymphs were placed in incubators at 15, 20, 25, 30, or 35 +/- 1 degrees C, 70 +/- 10% RH, and a 14-h photophase. The percentages of parasitism and emergence, the sex ratio, and the preimaginal period of T. radiata were determined. The fertility life table was developed from the biological data. The highest parasitism rate (77.24%) was obtained at a temperature of 26.3 degrees C, and the lowest parasitism rates occurred at 15 and 35 degrees C (23.1 and 40.2%, respectively). The highest percentages of emergence of the parasitoid occurred at 25, 30, and 35 degrees C (86.7, 88.3, and 78.8%, respectively), with the calculated peak at 30.8 degrees C (89.90%). The duration of the preimaginal developmental period for both females and males of T. radiata was inversely proportional to temperature in the thermal range of 15-35 degrees C. The development of T. radiata occurred at all temperatures studied, and the highest viability of the preimaginal period occurred at 25 degrees C. The highest values of net reproductive rate and finite growth ratio (lambda) were observed at 25 degrees C, so that in each generation the population of T. radiata increased 126.79 times, higher than the values obtained at the other temperatures.     

Quality of different aphids as hosts of the parasitoid Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae)

Lysiphlebus testaceipes (Cresson) has a broad aphid host range; however the quality of these preys may interfere in its biological feature. This study aimed to evaluate the quality of three Macrosiphini, Brevicoryne brassicae (L.), Lipaphis erysimi (Kaltenbach) and Myzus persicae (Sulzer), and three Aphidini Schizaphis graminum (Rondani) Rhopalosiphum maidis (Fitch) and Aphis gossypii Glover as hosts to L. testaceipes and to determine the relation possible of host preference, of size and quality of the host. The tests were carried out in climatic chamber at 25 +/- 1 degrees C, RH 70 +/- 10% and 12h photophase. The parasitoid did not oviposite in B. brassicae and L. erysimi, while the other species were nutritionally suitable to the parasitoid. L. testaceipes showed preference for aphids from tribe Aphidini and these hosts presented better quality to the parasitoid when compared to Macrosiphini. Interactions among size, preference and quality between the Aphidini were found. L testaceipes showed preference (parasitism rate 76.7%) for R. maidis, the bigger host (hind tibia with 0.281 mm). This host provided bigger size (hind tibia with 0.49 mm) and higher emergence rate (95.6%) to the parasitoid when compared to A. gossypii (parasitism rate of 55.7%). Also the smaller host A. gossypii (0.266 mm) provided smaller size hind tibia (0.45 mm) and higher mortality of the parasitoid (emergence rate 72.1%). However, the development time was shorter and the longevity was higher in A. gossypii (6.3 and 5.4 days, respectively) when compared to the host R. maidis (6.7 and 3.8 days, respectively), and not been related to host size.     

Biology and host selection behaviour of the aphid hyperparasitoid Alloxysta victrix in association with the primary parasitoid Aphidius colemani and the host aphid Myzus persicae

The biology of the aphid hyperparasitoid Alloxysta victrix was investigated with respect to its interaction with the primary parasitoid Aphidius colemani and the host aphid Myzus persicae. Laboratory investigations of host selection behaviour indicated that naive A. victrix females could rapidly distinguish between unparasitized aphids and those parasitized by A. colemani, but showed little tendency to discriminate between aphids parasitized by the primary parasitoid three, five, seven, or ten days earlier (even though the latter were already mummified). Host suitability studies, in contrast, indicated that aphids parasitized by A. colemani became progressively less suitable as the primary parasitoid developed. When aphids were exposed to A. victrix more than seven days after being parasitized by A. colemani, survivorship of both primary and secondary parasitoid species decreased, with a significantly higher proportion of mummies producing no viable adult parasitoid of either species. The developmental period (egg to adult eclosion) of surviving hyperparasitoids was also longer in older host stages, and females developed significantly more slowly than males (14.2 days versus 13.6 days, respectively). The sex ratio of hyperparasitoid broods emerging from all host stages was consistently male-biased (31–46% female), but adult longevity was higher for females than for males (37.1 days versus 23.6 days).     

褐带蚜小蜂成虫生物学特性

[目的]褐带蚜小蜂Aphelinus maculatus是近几年发现的棉蚜Aphis gossypii重要寄生蜂之一.目前关于该寄生蜂生物学特性包括行为习性方面的研究非常少.为有效挖掘利用褐带蚜小蜂,对其成虫生物学特性进行了研究.[方法]在室内采取体视显微镜下观察和记录褐带蚜小蜂的羽化节律、交配行为、交配各阶段持续时间...     

Effect of temperature on the development and viability of Gryon gallardoi (Brethes) (Hymenoptera: Scelionidae) parasitizing Spartocera dentiventris (Berg) (Hemiptera: Coreidae) eggs.

The development and viability of Gryon gallardoi (Brethes) (Hym.: Scelionidae) in Spartocera dentiventris (Berg) (Hem.: Coreidae) eggs were studied under four temperatures: 15, 20, 25, and 30 +/- 1 degree C, with a 12-h photophase. No parasitoid developed at 15 degrees C. Otherwise, viability reached 98.8% without varying significantly over the temperature range tested. The duration of development for males and females was inversely proportional to the temperature increase, varying respectively from 46.2 +/- 0.13 and 47.1 +/- 0.11 days (20 degrees C) to 13.3 +/- 0.07 and 13.4 +/- 0.06 days (30 degrees C). Males developed faster than females. The values estimated for the lowest thermic thresholds of development and the thermic constants were 15.5 degrees C and 185.19 DD for males and 15.6 degrees C and 192.31 DD for females, respectively. Given the average weather conditions in Porto Alegre, RS (30 degrees 01' S and 51 degrees 13' W), Brazil, G. gallardoi could annually produce 8.54 and 8.07 generations of males and females, respectively. The low rates of parasitism observed in the field during the first generation of its host may be due to the small number of G. gallardoi generations in this period.     

Development of the parasitoid,Cotesia rubecula (Hymenoptera: Braconidae) in Pieris rapae and Pieris brassicae (Lepidoptera: Pieridae): evidence for host regulation

Several recent models examining the developmental strategies of parasitoids attacking hosts which continue feeding and growing after parasitism (=koinobiont parasitoids) assume that host quality is a non-linear function of host size at oviposition. We tested this assumption by comparing the growth and development of males of the solitary koinobiont endoparasitoid, Cotesia rubecula, in first (L1) to third (L3) larval instars of its preferred host, Pieris rapae and in a less preferred host, Pieris brassicae. Beginning 3 days after parasitism, hosts were dissected daily, and both host and parasitoid dry mass was determined. Using data on parasitoid dry mass, we measured the mean relative growth rate of C. rubecula, and compared the trajectories of larval growth of the parasitoid during the larval and pupal stages using non-linear equations. Parasitoids generally survived better, completed development faster, and grew larger in earlier than in later instars of both host species, and adult wasps emerging from P. rapae were significantly larger than wasps emerging from all corresponding instars of P. brassicae. During their early larval stages, parasitoids grew most slowly in L1 P. rapae, whereas in all other host classes of both host species growth to pupation proceeded fairly uniformly. The growth of both host species was markedly reduced after parasitism compared with controls, with the development of P. brassicae arrested at an earlier stage, and at a smaller body mass, than P. rapae. Our results suggest that C. rubecula regulates certain biochemical processes more effectively in P. rapae than in P. brassicae, in accordance with its own nutritional and physiological requirements. Furthermore, we propose that, for parasitoids such as C. rubecula, which do not consume all host tissues prior to pupation, that parasitoid size and host quality may vary independently of host size at oviposition and at larval parasitoid egression.     

Impact of the entomopathogenic fungus Verticillium lecanii on development of an aphid parasitoid, Aphidius colemani

The parasitoid Aphidius colemani developed normally (approximately 90% adult emergence) when its cotton aphid (Aphis gossypii) host was treated with Verticillum lecanii conidia 5 or 7 days after parasitization. Fungus exposure 1 day before or up to 3 days after parasitization, however, reduced A. colemani emergence from 0 to 10%. Also, numbers of spores and mycelial fragments in aphid homogenates were much higher in aphids exposed to the fungus up to 3 days after parasitization than in aphids treated after 5 or 7 days. Our results suggest that the parasitoid and fungus may be used together for aphid biocontrol as long as fungus applications are timed to allow late-instar development of the parasitoid.     

Psyttalia ponerophaga (Hymenoptera: Braconidae) as a potential biological control agent of olive fruit fly Bactrocera oleae (Diptera: Tephritidae) in California

The olive fruit fly, Bactrocera oleae (Rossi), is a newly invasive, significant threat to California's olive industry. As part of a classical biological control programme, Psyttalia ponerophaga (Silvestri) was imported to California from Pakistan and evaluated in quarantine. Biological parameters that would improve rearing and field-release protocols and permit comparisons to other olive fruit fly biological control agents were measured. Potential barriers to the successful establishment of P. ponerophaga, including the geographic origins of parasitoid and pest populations and constraints imposed by fruit size, were also evaluated as part of this investigation. Under insectary conditions, all larval stages except neonates were acceptable hosts. Provided a choice of host ages, the parasitoids' host-searching and oviposition preferences were a positive function of host age, with most offspring reared from hosts attacked as third instars. Immature developmental time was a negative function of tested temperatures, ranging from 25.5 to 12.4 days at 22 and 30 degrees C, respectively. Evaluation of adult longevity, at constant temperatures ranging from 15 to 34 degrees C, showed that P. ponerophaga had a broad tolerance of temperature, living from 3 to 34 days at 34 and 15 degrees C, respectively. Lifetime fecundity was 18.7 +/- 2.8 adult offspring per female, with most eggs deposited within 12 days after adult eclosion. Olive size affected parasitoid performance, with lower parasitism levels on hosts feeding in larger olives. The implications of these findings are discussed with respect to field manipulation and selection of parasitoid species for olive fruit fly biological control in California and worldwide.     

班氏跳小蜂对新寄主资源的寄生适合度

【目的】班氏跳小蜂Aenasius bambawalei是扶桑绵粉蚧Phenacoccus solenopsis的伴迁性天敌,迄今已知该寄生蜂只能寄生扶桑绵粉蚧,但是我们发现该寄生蜂还能成功寄生另一种外来有害生物——石蒜绵粉蚧P. solani。本研究旨在明确班氏跳小蜂对该新寄主资源的寄生适合度,为今后充分开发、利用该寄生蜂提供科学依据。【方法】在实验室条件下,以马铃薯Solanum tuberosum块茎作为粉蚧的寄主植物,测定了班氏跳小蜂对不同龄期石蒜绵粉蚧的寄生适合度,并在非选择条件下测定了上述两种寄主上僵蚧形成时间以及该寄生蜂羽化时间、寿命、后足胫节长度、寄生率、羽化率及子代性比。【结果】班氏跳小蜂可寄生石蒜绵粉蚧的雌成虫及2龄和3龄若虫,但只有寄生雌成虫才能正常羽化出蜂。分别以石蒜绵粉蚧与扶桑绵粉蚧为寄主时,最适合的蜂蚧比分别为2∶15和2∶20。不同寄主对僵蚧形成时间及班氏跳小蜂的羽化时间无显著影响,但显著影响班氏跳小蜂的寿命以及雌蜂后足胫节长度,尤其是扶桑绵粉蚧上羽化的寄生蜂的寿命比以石蒜绵粉蚧上的长约20 d。而且,班氏跳小蜂对扶桑绵粉蚧的寄生率(54.0%)显著高于对石蒜绵粉蚧的(25.3%),但班氏跳小蜂在这两种寄主上的羽化率均在90%以上,差异不显著;寄生扶桑绵粉蚧的雌蜂比例高于寄生石蒜绵粉蚧的雌蜂比例。【结论】班氏跳小蜂能寄生石蒜绵粉蚧,且只在雌成虫上完成世代发育;与在更适寄主扶桑绵粉蚧上比较,石蒜绵粉蚧上羽化的班氏跳小蜂在寿命及雌蜂个体大小上有劣势。     

Host Age Choice for Oviposition in Pauesia juniperorum (Hymenoptera: Braconidae: Aphidiinae) and its Effect on the Parasitoid's Biology and Host Population Growth

Pauesia juniperorum has been selected as a potential agent for the biological control of Cinara cupressivora, an important introduced pest of conifers in Africa. As part of the pre-introductory assessment studies, selection of different host age categories for oviposition was studied in choice and no choice experiments. The duration of development and adult size of parasitoid progeny developing in different host age categories were compared. The effects of parasitism on survival and reproduction of five categories of the apterous morph of the host ranging in age from 3-15 days was also studied. The age of hosts had a significant influence on the degree with which different categories were parasitized. Host defensive behaviour, which increased with age, influenced the outcome of attempts by the parasitoid to oviposit. The effect was greater in older hosts, but in young hosts their small size was more important in enabling aphids to escape parasitism. The duration of development decreased while adult size increased with age of hosts. This demonstrated that fitness attributes of P. juniperorum were affected by larval ontogeny with older/larger hosts being more optimal. The ability of the parasitoid to exploit hosts of varying age was suggestive of a high degree of phenotypic plasticity which is potentially of adaptive value. Hosts parasitized before they were 9-days-old became mummies without reproducing. Those that were 9 days or older achieved part of their reproductive capacity before dying. Thus, the impact of P. juniperorum is markedly reduced when attacking older hosts.     

Larval competition between Aphidius ervi and Praon volucre (Hymenoptera: Braconidae: Aphidiinae) in Macrosiphum euphorbiae (Hemiptera: Aphididae)

Interspecific competition between parasitoid larvae may influence the size, structure, and stability of the population, leading to a reduction in total parasitism and thus restricting the pest control. Aphidius ervi (Haliday) and Praon volucre (Haliday) are endoparasitoids that possess a wide host range and present considerable potential for the biological control of the aphid Macrosiphum euphorbiae (Thomas). The larval competition between A. ervi and P. volucre, and the possible intrinsic competitive superiority of one of the parasitoids in M. euphorbiae, have been studied. In single parasitism experiments, mated parasitoid females (n=10) were maintained individually in contact with M. euphorbiae hosts (n=30) inside petri dishes containing lettuce leaf discs and maintained in environmental chamber at 22 ± 1°C, 70 ± 10% RH, and 12-h photophase. The multiple parasitism experiments consisted of exposing single parasitized aphids (n=120) to the second parasitoid species. Two oviposition events were performed with a 4-h interval between them, namely the following: sequence A (oviposition by A. ervi, followed by P. volucre) and sequence B (oviposition by P. volucre, followed by A. ervi). Oviposition sequence A generated 24 A. ervi and 55 P. volucre adults, whereas oviposition sequence B generated 23 and 49 adults. P. volucre is an intrinsically superior competitor compared with A. ervi, and the use of the two species simultaneously may result in competitive exclusion and influence the stability of the parasitoid population.     

Biology and thermal requirements of Trichogramma atopovirilia Oatman & Platner (Hymenoptera: Trichogrammatidae) parasitizing eggs of Diaphania hyalinata L. (Lepidoptera: Pyralidae)

The development and parasitism of Diaphania hyalinata L. eggs by Trichogramma atopovirilia Oatman & Platner and its thermal requirements were studied at the temperatures of 18, 21, 24, 27, 30 and 33 degrees C. Thirty eggs of D. hyalinata were exposed to three females of T. atopovirilia for 5h at 25 degrees C and incubated at the different temperatures. The developmental time from egg exposure to adult, parasitism viability, number of adults per parasitized host egg and progeny sex ratio were monitored. The developmental time from egg to adult emergence of the parasitoid exhibited inverse relationship to the temperature, lasting 24.12 days at 18 degrees C and 7.36 days at 33 degrees C. Parasitism viability at 24, 27 and 30 degrees C was higher than 90%. The ratio of T. atapovirilia adult produced per egg and its sex ratio were not affected when using D. hialynata as host. The lowest threshold temperature (Tb) and estimated degree-days over Tb required by T. atopovirilia to develop on eggs of D. hyalinata was 11.99 degrees C and 130.42 masculine C, respectively. Considering the temperature regimes of two areas where cucurbitaces are cultivated in Bahia State (Rio Real and Inhambupe County) it was estimated that T. atopovirilia can achieve more than 32 generation per year. The results suggest that T. atopovirilia has potential to control D. hyalinata eggs with better chance of success under temperature regimes ranging from 24 to 27 degrees C that meets the suitable field conditions for cropping cucurbitaces.     

可疑柄瘤蚜茧蜂对高温下不同龄期黑豆蚜的寄生及其适合度表现

研究寄生蜂对寄主不同龄期的寄生策略通常采用适温下（≈25℃）培养的寄主进行试验。 为探究蚜茧蜂对高温下生长的寄主蚜虫的寄生反应及其适合度表现,在30℃条件下饲养寄主孤雌胎生无翅黑豆蚜Aphis fabae Scopli,获得不同龄期若蚜和刚羽化的成蚜,分别提供给可疑柄瘤蚜茧蜂Lysiphlebus ambiguous Haliday寄生,观察蚜茧蜂的寄生率以及后代性比、体型大小和发育时间等适合度相关特性。结果表明： 可疑柄瘤蚜茧蜂对1至4龄若蚜及成蚜均寄生,但偏向寄生较早龄期的若蚜,对成蚜的寄生率为28.0％,显著低于对1龄（400％）和2龄（42.8%）寄主若蚜的寄生率。后代雌蜂比例和体型随寄主龄期（体型）增大而减小,而发育历期则呈现“中间低,两头高”的格局。后代性比、体型大小及发育历期等适合度表现与此前适温（≈25℃）下得到的结果截然相反。因此推测,寄主黑豆蚜体型或龄期可能不是或不全部是可疑柄瘤蚜茧蜂评价寄主质量的依据,其他与寄主蚜虫内共生菌动态相关的线索（如行为的,化学的等）可能才是其评价寄主质量的依据。     

Effects of egg age of Spartocera dentiventris (Berg) (Hemiptera: Coreidae) on parasitism by Gryon gallardoi (Brethes) (Hymenoptera: Scelionidae)

To evaluate the effect of egg age of Spartocera dentiventris (Berg) on the parasitism by Gryon gallardoi (Brethes), groups of 12 eggs of 2, 3, 4, 5, 6, 7, 8, and 12 days old were exposed to one female of G. gallardoi on a test tube, with the wasp observed for 2h subsequently. Later, the eggs were individualised and incubated (25 +/- 1 degrees C; 12h photoperiod) until adult emergence. To identify the preferred age, groups of 12 eggs of 1, 3, 5, 7 and 12 days of age were simultaneously exposed to a parasitoid female on an arena for 2h. These groups were also individualised and incubated until parasitism was confirmed. On all ages tested parasitism was at about 88.5 +/- 2.64%, with a reduction in adult parasitoid emergence with age increasing (P < 0.01). The development time increased with increasing egg age (P < 0.01), with males developing faster. Parasitoid sex ratio for all ages tested was female-biased (0.49:1), with the proportion of males invariant with host age (P > 0.05). When the egg groups were exposed simultaneously, the female preferred eggs one and three days old. The results indicate a preference of G gallardoi for younger eggs of S. dentiventris, with host egg age exerting a negative effect on development time and offspring emergence of the parasitoid.     

椰心叶甲蛹寄生蜂——椰心叶甲啮小蜂的生物学特性

椰心叶甲啮小蜂Tetrastichus brontispae Ferrière是椰心叶甲Brontispa longissima（Gestro）蛹的重要内寄生蜂,2004年从台湾引入到海南。在实验室条件下,对椰心叶甲啮小蜂的形态、行为、发育、存活、繁殖等生物学特性进行了观察研究。结果表明,雌蜂个体比雄蜂大,腹部明显可见产卵器。每头寄主蛹出蜂量平均为21.5头,其中雌蜂约占77.4%。椰心叶甲啮小蜂羽化不久即能交配,交配时间约为1～2 min。椰心叶甲啮小蜂的产卵高峰期在交配后的24 h内,且产卵量受温度的影响较大; 蜂蜜、蔗糖、葡萄糖均能有效地延长其成虫的寿命,并能提高其怀卵量和寄生率,其中以取食蜂蜜的效果最好。该蜂发育、存活和繁殖的适宜温度为20℃～28℃,低于16℃或高于30℃对其存活不利。利用16℃、20℃、24℃、28℃、30℃下的发育历期和有效积温公式计算出椰心叶甲啮小蜂的发育起点温度（C）为9.6℃,有效积温（K）为324.9日·度。