Reproductive biology of the microtype tachinid fly Zenillia dolosa (Meigen) (Diptera: Tachinidae)

Reproductive biology including mating, adult longevity, fecundity and development of the tachinid fly Zenillia dolosa was investigated for optimizing rearing procedures using Mythimna separata as a host in the laboratory. Females lay microtype eggs containing a first instar larva on food plants of the host and then the eggs must be ingested by the host for parasitization. Mating success was 58.5% with mating duration of 80.7 min. Mating was most successful when day 0–1 females were kept with day 2–4 male flies. Female body size was positively correlated with its fecundity but not with longevity. However, females that survived longer produced more eggs during their lifetime. Parasitoids successfully developed in 4th to 6th instar host larvae. Host instars at the time of parasitoid egg ingestion significantly influenced development time of the immature parasitoid, but did not affect body size of the emerging parasitoid. We suggest that pairing newly emerged females with day 2–4 males should result in higher mating success and using the last instar hosts for parasitization should minimize development time of the parasitoid for rearing.     

Neurosecretory cells in Diptera

The neurosecretory cells were studied in 20 dipteran species belonging to three suborders. The NSC are localized in (a) the frontal ganglion (in 10 of the 20 species studied), (b) the pars intercerebralis region of the protocerebrum (in the median and lateral groups), (c) the tritocerebral region of the brain (in 8 of the 20 species studied) and (d) the suboesophageal ganglion. In one species, NSC were also seen in the prothoracic ganglion. The NSC were classified as types A, B and C/D. The NSC of the median group of the pars intercerebralis were unusually large compared with the size of the brain. The number, size and distribution of the cells are discussed.     

春尺蠖生物学特性研究

【目的】为新疆北疆地区春尺蠖Apocheima cinerarius预测预报工作提供理论依据。【方法】本文在林间对春尺蠖的各虫态进行详细调查,记述了各虫态的形态特征、生活史、性比、行为与习性。【结果】春尺蠖蛹主要集中分布在树盘基部30~60 cm、土壤深度为20~30 cm范围的土层中,成虫羽化后,次日19:00—23:00或第3天下午4:00—6:00交尾,其交配行为是多次交配型。雌虫比雄虫羽化稍早,雌虫平均寿命为16~18 d,雄虫平均寿命为8~13 d。翌日黄昏开始产卵,卵期最长34 d,最短26 d,雌虫每天平均产卵块数最高达5.1块/头、平均卵粒数为363.1粒/头,最低为1块/头、平均卵粒数为86粒/头,平均孵化率为86%。1、2龄幼虫食叶量较低,3龄开始暴增,5龄最高,平均每日食叶量可达443 mm2/头。【结论】春尺蠖成虫按翅面斑纹和颜色,可分三种类型:深色型、常见型、浅色型。幼虫的头壳与虫龄呈显著直线正相关。幼虫1~2龄期间,死亡率较高,高达60.37%;4~5龄幼虫,死亡率较低,且食叶量占总食叶量的85.81%。所以应选择在3龄幼虫高峰期之前进行防治。雌雄比为1︰0.7068,可预测下一代种群数量呈上升趋势。     

Neurosecretory activity as related to feeding,mating, and oögenesis in the female cave tick, Ornithodoros tholozani

In virgin females neurosecretory activity increased immediately after feeding. This is probably related to gut stretching. After one hour NSC numbers decreased until 48 hr after feeding. Thereafter NSC numbers showed oscillations until the 10th day. During this period rapid blood digestion takes place. The peak in NSC numbers found on the 10th day can be related to high O₂ consumption and high protease activity. The peak in NSC number on the 14th day is possibly related to gut epithelial-cell proliferation. In mated and starved females no changes in NSC numbers could be found. Only when these females were fed, a marked increase in NSC was observed. A rise in NSC numbers observed during the period 5 to 15 days after mating could be related to oögenesis. Egg laying stimulated NS activity. It was found that certain types of NSC were connected with this phenomenon. A scheme is suggested to explain the interrelationship between the NSC in the CNS and physiological phenomena.     

Synthesis of the same two proteins prior to larval diapause and pupation in the spruce budworm,Choristoneura fumiferana

Spruce budworm larvae produce large quantities of two proteins (Choristoneura fumiferana diapause associated proteins 1 and 2, CfDAP1 and CfDAP2) that are diapause related. These proteins appeared soon after hatching and increased in abundance, reaching maximum levels by four days into the 1st instar, and they remained at high levels until three days after the termination of diapause. These two proteins were purified to homogeneity and their NH2-terminal sequences were obtained. Oligonucleotide primers designed on the basis of these NH2-terminal sequences were used in RT-PCR to isolate the cDNA fragments coding for these proteins. These PCR fragments were then used as probes to isolate the cDNAs that contained the complete coding region. The 2.5kb mRNAs coding for these proteins started to appear 24hr after hatching and large quantities of these mRNAs were detected in 1st instar and 2nd instar larvae until the 2nd instar larvae entered diapause. Low levels of these mRNAs were detected in the 2nd instar larvae that were preparing to enter diapause, in those that were in diapause as well as in those that terminated diapause. Low levels of CfDAP1 mRNA were also detected on days 1 and 2 after ecdysis to the 3rd instar. However, no CfDAP1 and CfDAP2 mRNAs could be detected during the 4th and 5th instar larval stages. The mRNAs reappeared 24hr after the 5th instar larvae molted into the 6th instar and increased to reach maximum levels by 60hr after ecdysis. The mRNA levels remained high until 156hr after ecdysis into the 6th instar (36-48hr before pupal ecdysis), after which they disappeared once again. Immunocytochemical analyses showed that CfDAP1 protein was present in 2nd and 6th instar larval fat body but not in 5th instar larval fat body. Thus, the same two genes were expressed for the first time before C. fumiferana larvae entered diapause and for a 2nd time before pupation.     

玫烟色拟青霉对小菜蛾致病力的时间-剂量-死亡率模型模拟

小菜蛾Plutella xylostella是我国南方十字花科蔬菜上的重要害虫,已对田间常用的化学杀虫剂产生了严重的抗性。为寻找有效的小菜蛾生物防治措施,本实验研究了一株分离自家白蚁的玫烟色拟青霉Paecilomyces fumosoroseus (SCAU-PFCF01)对小菜蛾2～4龄幼虫的致病力。实验采用浸液法,供试浓度为1×10³、1×10⁴、1×10⁵、1×10⁶和1×10⁷个孢子/mL。结果表明：随玫烟色拟青霉孢子浓度的升高,小菜蛾的感病死亡率增加,在浓度为1×10⁷ /mL时,小菜蛾2、3和4龄幼虫的累计死亡率分别为96%、85%和80%。玫烟色拟青霉对小菜蛾各龄幼虫的致病力与供试龄期有关,其感病的敏感顺序为2龄、3龄和4龄。用时间 剂量 死亡率模型（time-dose-mortality model,TDM）对各龄幼虫的致病力数据进行模拟,所建模型均顺利通过Hosmer-Lemeshow拟合异质性检验,表明模型拟合良好,并由模型估计出了该菌株对小菜蛾各龄幼虫的致死剂量与致死时间。2龄幼虫接种后第7天、3龄幼虫接种后第5天、4龄幼虫接种后第4天的LC₅₀估计值分别为1.17×10⁴、1.44×10⁴和5.21×10⁴ /mL,LC₉₀估计值分别为1.98×10⁶、3.82×10⁷和1.29×10⁸ /mL。玫烟色拟青霉对小菜蛾幼虫的致死时间与浓度相关,供试各龄幼虫的LT₅₀值随着孢子悬浮液浓度的增加而递减,在1×10⁵～1×10⁷ /mL的范围内,2龄幼虫的LT₅₀值从3.16天降低到1.72天,3龄幼虫的LT₅₀从3.21天降低到1.83天,4龄幼虫的LT₅₀从3.69天降低到2.04天。即2龄幼虫致死所需的时间最短,其次为3龄幼虫,4龄幼虫致死所需的时间最长。结果显示了该株玫烟色拟青霉在小菜蛾的生物防治中具较强的应用潜力。     

Relation of feeding,growth, and metabolism to age in the larval,female house cricket

The maximum growth rate occurs in the first half of the 7th and 8th larval instars of the house cricket, at which time food and water consumption is maximal. Growth ceases in the last 2 to 3 days of each instar when food consumption is almost nil. The metabolic rate is twice, and the locomotory activity is four times, higher in the first 2 to 3 days than in the last 2 to 3 days of each instar. The %-gain in dry wt is 120% for the 7th and 139% for the 8th instar. The average digestive coefficient (AD) for the 8th instar is 67% and the average efficiency of food conversion to tissue (dry wt ECI) is 27%. The average daily food consumption for 8th instar larvae is 31.4 mg, and, therefore, we calculate that an average of 12 mg food is burnt per day for energy which is confirmed by the observed average V_O2 of 1.2 ml O₂/g-cricket/hr. Total lipids as %-total wt (239% mg-gain) increases in the first 4 days then remains constant in spite of cessation of feeding in the last 2 days. The RQ confirms the conversion of carbohydrates to lipids in the first half of each instar. In the moulting cycle carbohydrates are used for maintenance (when not feeding), but lipids are used at apolysis.     

The two duplicated insecticyanin genes, ins-a and ins-b are differentially expressed in the tobacco hornworm, Manduca sexta.

Two gene-specific probes were generated from the unique sequences in the 3' non-coding regions of the two insecticyanin genes, ins-a and ins-b to study the developmental expression of these genes in Manduca sexta. Both genes were initially transcribed in the freshly hatched first instar larvae and then expressed in the epidermis and to a lesser degree in the fat body during every larval feeding stage. In the epidermis of the 4th and 5th instar larvae, both mRNAs appeared shortly before ecdysis and accumulated to maximal levels within a day. As the larval epidermis became pupally committed on day 3 of the 5th (final) instar, INS-a mRNA quickly decreased, whereas INS-b mRNA showed a second peak of accumulation. In the fat body, both genes showed a similar expression pattern within the 4th instar to that of the epidermis except that levels were lower and ins-b mRNA dominated. In the final instar, only ins-b mRNA was present in significant amount. These findings not only reveal that the two duplicated insecticyanin genes have diverged in their expression pattern but also demonstrate, for the first time, that fat body also expresses insecticyanin genes.     

Haemolymph levels of juvenile hormone,ecdysteroids and protein during the last two larval instars of Locusta migratoria

The radioimmunoassay of ecdysteroids and juvenile hormone has enabled us to relate hormone levels to haemolymph protein concentrations and weight increase during the 4th and 5th instar of the migratory locust. The two hormones are never present in high concentrations in the blood simultaneously. The levels of ecdysteroids are high on the 5th day during the 4th larval stage: they show a small peak on the 3rd day, and then a large peak on the 8th day during the 5th instar. JHI-immunoreactive substances are high during the first 4 days of the 4th instar, and during the first 5 hr during the 5th instar. Protein concentrations in the haemolymph begin to rise when ecdysteroid levels increase during stage 4, and immediately after the small peak (on day 3) in the 4th stage larva. The rise in protein levels is correlated with an increase in weight.     

饥饿程度对美国白蛾生长发育和繁殖的影响

不同龄期幼虫饥饿对美国白蛾Hyphantria cunea(Drury)生长发育和繁殖影响的研究结果表明:美国白蛾低龄(2龄)幼虫短时间的饥饿对其生长发育和繁殖的影响不明显;美国白蛾中龄(4龄)幼虫饥饿2,4,6d使美国白蛾的历期相应增长,存活率、化蛹率、羽化率、产卵量都相应降低,交配率与对照之间没有差异;老熟(6龄)幼虫短时间饥饿(4d)的存活率、羽化率、交配率、产卵量都稍有下降;长时间饥饿(12d)的老熟幼虫有70%左右因饥饿而提前化蛹,提前化蛹的蛹体外没有薄茧的包裹。提前化蛹的美国白蛾的羽化率、交配率均非常低,产卵量很少。     

麻疯树柄细蛾形态和生物学特性观察

麻疯树柄细蛾Stomphastis thraustica Meyrick是在我国新发现的麻疯树Jatropha curcas L.潜叶蛾类重要害虫。通过室内饲养与野外调查相结合对该虫形态、发育习性及生活史进行了研究。本文对麻疯树柄细蛾成虫、卵、各龄幼虫和蛹的形态及大小进行了详细描述。95.54%(n=426)的老熟幼虫在10点至18点结茧。89.19%（n=111）在夜间20点至次日凌晨6点羽化。交配在清晨进行, 持续30~210 min不等。87.53%（n=441）的卵在夜间20点以后至次日6点以前产出。卵多产于叶脉边缘与叶片形成的凹陷处。66.77%（n=8 266）的卵产于叶片背面, 其余产于叶片正面。每雌产卵平均60.03粒(n=32)。麻疯树柄细蛾在攀枝花全年均可发育。以成虫在每年2月至5月越冬。一年发生10代以上, 世代重叠明显。以6月室外平均气温25.15℃条件下, 全世代发育需18~20 d。卵期3~4 d, 1龄幼虫期1 d, 2龄幼虫期1~2 d, 3龄幼虫期1~2 d, 4龄幼虫期1~2 d, 5龄幼虫期2~3 d, 预蛹期1 d, 蛹期4~6 d, 成虫产卵前期1 d。     

Growth and development of Encarsia formosa (Hymenoptera: Aphelinidae) in the greenhouse whitefly, Trialeurodes vaporariorum (Homoptera: Aleyrodidae): effect of host age

The tiny parasitoid wasp, Encarsia formosa, has been used successfully to control greenhouse whiteflies (GHWFs) in greenhouses in many countries throughout the world. Therefore, there has been considerable interest in developing methods for artificially rearing this wasp. However, little information is available concerning the regulation of its development including the host-parasitoid interactions that are required for the parasitoid to complete its life cycle. Here we confirm that parasitoid developmental rates differ significantly based upon the host instar parasitized. Development was faster when 3rd and 4th instar GHWFs were offered for parasitization than when 1st or 2nd instars were used. Our results show that it is primarily the embryo and the first two parasitoid instars that exhibit prolonged developmental times when 1st and 2nd instar whiteflies are parasitized. Although percent emergence was not affected by host age at the time of parasitization, adult longevity as well as adult emergence pattern varied greatly depending upon the instar parasitized. When 3rd and 4th instar GHWFs were selected for oviposition, adult wasps lived significantly longer than when 1st or 2nd instars were used; also, there was a sharp emergence peak on the 2nd day after emergence was first observed (reduced or absent when 1st or 2nd instar GHWFs were parasitized) and the emergence period was reduced from between 8 and 11 days to 5 days. In general, the younger the host instar parasitized, the less synchronous was parasitoid development. Previous reports that E. formosa will not molt to the 2nd instar until the host has reached its 4th instar were not confirmed. When 1st instar host nymphs were parasitized, 2nd instar parasitoids were detected in 3rd instar hosts. Importantly, however, no matter which instar was parasitized, the parasitoid never molted to its last instar until the host had reached Stage 5 of its last instar, a stage in which host pharate adult formation has been initiated. It appears, then, that a condition(s) associated with host pharate adult formation is required for the parasitoid's final larval molt. Results reported here should facilitate the development of in vitro rearing systems for E. formosa.     

Neuroendocrine regulation of corpus allatum activity in Manduca sexta: The endocrine basis for starvation-induced supernumerary larval moult

When newly-ecdysed 5th instar larvae of Manduca sexta were starved for 3 days and thereafter fed on standard diet the majority (90%) of the surviving larvae moulted into 6th instars. Allatectomy prior to starvation abolished the supernumerary moult, while denervation of the corpora allata (CA) had no effect.Cautery of medial neurosecretory cells, but not of the lateral cells, prevented supernumerary moulting and pupation ensued. Transplantation of brains from young 5th instar donors into larvae, whose medial neurosecretory cells were cauterized prior to starvation, restored the extra larval moult. Neither CA nor corpora cardiaca (CC) could be substituted for the medial neurosecretory cells.For induction of the supernumerary moult the medial neurosecretory cells are required only until day 1 after refeeding whereas the CA are required until day 3 after refeeding. Allatectomy on day 3 after refeeding resulted in the production of black 6th instar larvae.We conclude that starvation-induced supernumerary moulting is due to activation of the CA by allatotropin produced by medial neurosecretory cells in the brain. The anteromedial cells (group II) appear to be the source of allatotropin.     

Evidence for the presence of a threshold weight for entering diapause in the yellow-spotted longicorn beetle, Psacothea hilaris

Under long-day conditions larvae of Psacothea hilaris (Coleoptera: Cerambycidae) pupate after the 4th or 5th instar, while under short-day conditions they undergo 2-4 nonstationary supernumerary molts and eventually enter diapause. To explore the possibility of a threshold weight for entering diapause, P. hilaris larvae were deprived of food on days 0 (day of ecdysis), 4 or 8 of the 4th, 5th and 6th instars under short-day conditions. Within the first 40 days of starvation, 60% of the larvae starved starting on day 0 of the 4th instar died, but all the larvae starved at later stages survived. The incidence of diapause in these survivors was determined by the occurrence of pupation after a temporary chilling at 15 degrees C for 15 days. Diapause incidence increased as the onset of starvation was delayed; from 11% in the larvae starved on day 0 of the 5th instar to 100% in the larvae starved on day 4 and day 8 of the 6th instar. Analysis of the relationship between the initial weight of a respective larva at the onset of starvation and its pupation success revealed that none of the larvae weighing 690 mg did. This finding suggests the presence of a threshold weight (about 600 mg), below which larvae are incapable of entering diapause. We discuss these findings with reference to the life history of P. hilaris.     

Titres of biogenic amines and ecdysteroids: effect of octopamine on the production of ecdysteroids in the silkworm Bombyx mori

At day two, a sharp peak of octopamine (OA) was observed in last instar female Bombyx mori larvae. This peak also appeared in male larvae a day later than in females at day three. An OA peak was also observed before the 3rd ecdysis. However, no OA peaks were observed in 4th instar larvae. At day eight and nine of the 5th instar, another OA peak was observed for male and female, respectively. A peak of tyramine (TA) was found at day one followed by a peak of OA at day two in 3rd instar larvae. At day two, a day before OA peak, a peak of TA was observed for male insects and before the 2nd peak of OA, TA titre was also high in 5th instar larvae. Immediately after 3rd ecdysis, a high titre of DL-beta-(3,4-dihydroxyphenyl)alanine (DOPA) was observed, followed by a peak of dopamine (DA) at day five. A peak of DOPA was found at day one followed by a peak of DA at day two in 3rd instar larvae. Similarly, a small peak of DOPA was observed at day two, followed by an increase of DA at days eight and nine after the 4th ecdysis. Ecdysteroid peaks were observed just before the 3rd and 4th ecdysis and an ecdysteroid titre increased after the start of spinning. The effects of OA and JH on production of ecdysteroids by prothoracic glands (PGs) were examined in order to identify neuromediators responsible for triggering pupation in B. mori larvae. Exogeneous OA (10-100 mM) reduced and 10 &mgr;M OA stimulated the production of ecdysteroids in the presence and absence of brain extracts by PGs in the final instar (day five) of B. mori in vitro. Meanwhile, exogeneous JHI (10 &mgr;g/ml) stimulated and at 5 &mgr;g/ml it reduced production of ecdysteroids in the presence of brain extracts. Gramine, an OA antagonist, delayed pupation when applied in the diet. Thus, OA may produce some biological effects on the programming of larval-pupal development.     

Sexual size dimorphism in the two spot ladybird beetle Adalia bipunctata: developmental mechanism and its consequences for mating

Abstract  1. The literature on ladybirds indicates that males are consistently smaller than females but take the same length of time to complete their development. Rearing Adalia bipunctata at 20 and 25 °C confirmed that protandry cannot account for sexual size dimorphism in this species, nor can a difference in egg size.
2. Female larvae consumed more food and had a higher relative growth rate in the fourth instar than did male larvae.
3. When food is limited, small males appear to be more successful at mating than are large males.
4. To account for these results, it is hypothesised that the gonads of male larvae compete more strongly with the soma for resources and that this reduces the growth potential of the soma of male larvae relative to that of female larvae. The greater mating success of small males when food is limited supports the eat or mate hypothesis, which predicts that when food is limited small males will spend less time feeding and more time mating than will large males.     

Stage-dependent effects of 20-hydroxyecdysone on DNA synthesis of corpus allatum cells in the silkworm,Bombyx mori

DNA synthesis in cells of the corpus allata (CA) of the silkworm, Bombyx mori, was studied immunocytochemically after in vivo labeling with 5-bromo-2'-deoxyuridine (BrdU); developmental changes during the 3rd, 4th, and last larval instars and effects of 20-hydroxyecdysone treatment were examined. During both the 3rd and 4th larval instars, the number of DNA-synthesizing cells fluctuated, and relatively low levels were observed during the middle stages. On day 0 of the last larval instar, the number of DNA-synthesizing cells per gland was 9.2, which then increased on day 1 and remained at levels ranging from 12.9 and 16.9 cells per gland. A major peak level (28 BrdU-labeled cells per gland) occurred on day 8, two days after larvae entered the wandering stage. When last instar larvae were fed 20-hydroxyecdysone-supplemented mulberry leaves starting on day 0 or 1, the number of DNA-synthesizing cells dramatically decreased to very low levels and these low levels were maintained throughout the remainder of the instar. However, no effect was observed when last instar larvae were fed 20-hydroxyecdysone-supplemented mulberry leaves starting on day 3, indicating the stage-specific action of 20-hydroxyecdysone. The mechanism by which 20-hydroxyecdysone treatment inhibits DNA synthesis of CA cells was further examined by using continuous in vitro BrdU labeling for a 2-day incubation. It was found that the decrease in responsiveness of DNA synthesis of CA cells of 20-hydroxyecdysone-treated larvae to stimulation by growth factors from hemolymph may have been, at least in part, responsible for the indirect inhibitory effects of 20-hydroxyecdysone.     

Endocrine manipulations,juvenile hormone and ontogenesis of male sexual behaviour in locusts

By injection of azadirachtin (AZA) to 5th instar hoppers of Locusta migratoria migratorioides, “over-aged” nymphs were produced, some of which survived for long periods without moulting to adults. Such over-aged male nymphs exhibited mating behaviour belatedly, though at a lower intensity than normal adults. Juvenile hormone (JH) markedly intensifies male sexual behaviour in crowded adult (6th instar) Locusta; thus, the lower intensity of sexual behaviour of the over-aged nymphs might have been caused by a low endogenous JH titre, or by a weaker response to the hormone. To clarify this point, chemically allatectomized over-aged 5th instar nymphs were produced by combined treatment with precocene and AZA. These exhibited a very low intensity of mating behaviour. Injections of exogenous JH III intensified the mating behaviour of the chemically allatectomized over-aged 5th instar male nymphs in a dose-dependent way, but the effect was weaker than in chemically allatectomized adult males. AZA-induced over-aged 4th instar male Locusta hoppers also exhibited mating behaviour. By injection of AZA, 5th instar over-aged hoppers of Schistocerca gregaria were also produced. Males showed mating behaviour belatedly, despite the fact that JH completely controls male sexual behaviour in this species. The intensity of this behaviour was again lower than in adults. Interrelations between integumental morphogenesis, “ethogenesis” of male sexual behaviour, and endocrine factors in locusts are discussed.