Multigenerational maternal inhibition of prepupal diapause in two Trichogramma species (Hymenoptera: Trichogrammatidae)

It is known that in some insect species the incidence of diapause among the progeny of females that had undergone diapause is relatively low or zero even under strong diapause-inducing conditions. Moreover, the maternal inhibition, preventing the induction of a maladaptive diapause in spring, can persist over several generations. This multigenerational effect based on hypothetical ‘interval timer’ was thoroughly studied in Aphididae. We first described a similar phenomenon in Hymenoptera: laboratory experiments demonstrated that the proportion of diapausing progeny of Trichogramma females that had undergone diapause was practically zero independently of photoperiodic and temperature conditions used (day lengths of 12 and 18 h and temperatures of 12–15 °C). Then the ability to enter diapause recovered gradually and returned to the normal level over two (in Trichogramma telengai) or even five (in Trichogramma principium) generations. We conclude that the observed effect may be based on an interval timer similar to that in aphids.     

Multigenerational maternal effect on diapause induction in Trichogramma species (Hymenoptera: Trichogrammatidae)

Maternal photoperiodic response is known to influence the percentage of diapausing prepupae in Trichogramma species. However, the influence of several preceding generations has not yet been studied. We have investigated the stability of photoperiod-induced changes in multiple generations of Trichogramma buesi Voegele and Trichogramma principium Sug. et Sor. Short-day conditions during preimaginal development induced an increase in the percentage of diapausing progeny and grand progeny of both Trichogramma species. A similar trend was also detected in the fourth and fifth generations, but the response was weak although statistically significant. This grand-grandmaternal photoperiodic effect (which has not been demonstrated before for Trichogramma or for any other insect parasitoid) is most probably based on the transgenerational transmission of variations in DNA expression. We conclude that in mass rearing, to facilitate diapause induction before cold storage, it is advisable to rear both maternal and grandmaternal generations under the short-day conditions. In scientific studies, several generations preceding the experiment should be kept under equal conditions to exclude multigenerational maternal effects.     

Maternal thermal effect on diapause in Trichogramma species (Hymenoptera: Trichogrammatidae)

Both direct thermal and maternal photoperiodic effects on diapause induction have been thoroughly investigated in many insect species, while maternal thermal effects have been infrequently studied. We studied the effect of temperature during development of maternal generation on the proportion of diapausing progeny in four species of the genus Trichogramma Westw., minute egg parasitoids, widely used for biological control of lepidopteran pests. The maternal generations were reared at day lengths of 12 and 18 h and temperatures of 17, 20, 25 and 30°C, and their progeny developed under day length of 12 h and temperatures of 13 and 14°C. In T. evanescens and T. piceum, the proportion of diapausing progeny decreased with increasing temperature under all tested photoperiods and thermal regimes of progeny development; the high temperature of 30°C totally averted diapause of progeny. In T. buesi and T. principium, low temperatures of 17 and 20°C resulted in relatively high proportion of diapausing progeny only when the maternal generation developed under short‐day conditions. The threshold of the maternal thermal response varied from 17–18 to 22–23°C. Under field conditions, Trichogramma females are exposed to such high temperatures only during summer, when diapause in their progeny is in any case prevented by the maternal photoperiodic response and by the thermal response of the larvae. We conclude that the maternal thermal effect on diapause induction, although to a different extent, is inherent to Trichogramma species but, at least as suggested by laboratory experiments, it does not play any role in the regulation of seasonal development under natural conditions. However, during mass rearing of Trichogramma wasps, it should be taken into account that high temperature, even when combined with short photoperiod, can avert diapause in the next generation.     

Cumulative induction of diapause in successive generations of Trichogramma species (Hymenoptera,Trichogrammatidae)

The ability of two Trichogramma species (Trichogramma telengai Sor. and T. principium Sug. et Sor.) to accumulate the effect of the maternal photoperiodic response during 5 consecutive generations reared in the laboratory under the short day (12 h) conditions was investigated. Control individuals developed at the same temperature of 20°C, but under the long day (18 h) conditions. The tendency to diapause was estimated by the proportion of progeny that entered diapause under the short day conditions at the temperatures of 13, 14 and 15°C. Trichogramma principium manifested an evident transgenerational cumulative photoperiodic response: the development of 1, 2, and 3 consecutive generations under the short day conditions caused a gradual increase in the proportion of diapausing progeny. In T. telengai, the progeny of the females that developed under the short day conditions also entered diapause more often than the progeny of those that developed under the long day conditions, but the number of preceding generations which developed under short day had no effect on the tendency to diapause. This interspecific difference can be possibly explained by the different natural geographic ranges of the two studied species. Trichogramma principium occurs in Southern Europe, Southern Kazakhstan, and Central Asia where the autumnal decrease in temperature is very slow and thus two or even more generations can develop under the short day conditions, whereas T. telengai is distributed over Central and North-Western Europe and in Siberia, where the autumnal decrease in temperature is rather fast, the development of one more “autumnal” generation is risky, and thus even the first “short-day signal” induces a very strong tendency of the progeny to diapause.     

Maternal influence on diapause induction in Trichogramma (Hymenoptera: Trichogrammatidae): the dynamics of photosensitivity

It is known that the prepupal diapause in Trichogramma is dependent on temperature conditions of embryonic and larval development and on the photoperiodic conditions of preimaginal development of maternal females. However, the relative photosensitivity of different preimaginal stages has been never investigated. We studied the position of the photosensitive period over the preimaginal development of maternal females in T. embryophagum Htg. and T. principium Sug. et Sor. by transferring preimaginal stages between diapause‐averting ‘long’ day (L : D = 20 : 4) and diapause‐inducing ‘short’ day (L : D = 12 : 12). Results showed that the influence of maternal photoperiod on progeny diapause was determined during the late pupal stage (last days of preimaginal development at 20°C). During this time, the critical duration of the photoperiodic induction was extremely small: one short or long day caused almost the same effect as the permanent development under these conditions. As a whole, photoperiodic response in Trichogramma was found to be unusually rapid, labile and easily reversible which is probably explained by extremely small size and fast development of these egg parasitoids. The results of this study could be used for elaboration of optimal methods for Trichogramma mass rearing and storage and for prediction of its seasonal cycles under natural conditions.     

Maternal thermal and photoperiodic effects on the progeny diapause in Trichogramma telengai Sorokina (Hymenoptera: Trichogrammatidae)

Although maternal photoperiodic and maternal thermal effects on the progeny diapause have been demonstrated in a number of insect species, their interaction has been rarely studied. We investigated this interaction in Trichogramma telengai. In a series of experiments, maternal females were reared at day lengths of 12–18 h and at temperatures of 17, 20, 25 and 30°C. Their progeny developed under day length of 12 h and temperatures of 13, 14 and 15°C. The experiments showed that both short day and low temperature experienced by the maternal generation significantly increased the proportion of diapausing progeny. In particular, the threshold of the maternal photoperiodic response decreased with temperature. Under combinations of photoperiod with daily thermoperiod, the role of the “night” temperature in the induction of diapause in the progeny was much more important than that of the “day” temperature. We conclude that the interaction pattern between the photoperiodic and thermal maternal effects in T. telengai is generally the same as that between the photoperiodic and thermal responses directly influencing diapause induction in other long‐day insects. The threshold temperature of the maternal thermal response of T. telengai was about 25–27°C, while diapause can be induced if larvae develop at temperatures not higher than 15–16°C. This suggests that, at least in the studied Trichogramma species, the maternal thermal effect has no ecological value. In the practice of biocontrol, however, rearing of Trichogramma wasps at high temperature can drastically reduce the proportion of diapausing progeny.     

Photo-thermal regulation of diapause in Trichogramma piceum Djur. (Hymenoptera, Trichogrammatidae)

Interaction of the photoperiodic conditions of development of maternal females (day lengths of 2 to 22 h at 20°C) with the thermal regime of development of their progeny (temperature of 12 to 15°C at day length of 12 h) in determination of prepupal diapause in Trichogramma piceum was studied under laboratory conditions. At 15°C the diapause was practically absent. At lower temperatures, the proportion of diapausing prepupae was maximal (25% of larvae at 14°C, 70% of larvae at 13°, and 80% of larvae at 12°C) if the maternal females developed under short day conditions (10–12 h). When maternal females developed at day lengths of 18–20 h, diapause was rarely recorded at all temperatures, while ultra-short (less than 8–10 h) days also caused a decrease in the proportion of diapausing progeny. The right (ecologically important) threshold of this maternal long-day photoperiodic response was about 14–15 h independently of the temperature during the progeny development. These results make it possible to clarify the mechanism of the “maternal photoperiodic correction of the progeny thermal response.” Although the impact of the maternal photoperiodic response can be revealed only within a very narrow thermal range, the relative strength of the diapause-inducing effect of different day lengths is independent of the temperature regimen of the progeny development.     

Molecular identification of two Trichogramma species (Hymenoptera: Trichogrammatidae) in Korea

Trichogramma wasps parasitize eggs of various insect species. Several Trichogramma species have been commercialized to manage Lepidopteran agricultural pests. Correct species identification is essential for successful biological control. However, the microscopic size and morphological similarity of Trichogramma species makes correct identification very difficult. Internal transcribed spacer (ITS)-2 gene sequences have been used to identify Trichogramma species. Using this molecular marker, Trichogramma species that are commercially available in Korea were identified as Trichogramma ostriniae and Trichogramma brassicae. The latter has not previously been reported in Korea. Additionally, Cadra cautella and Sitotroga cereallela eggs (host eggs of the commercialized Trichogramma species in Korea) were infected with Wolbachia. However, Trichogramma were not infected with the bacterium. This indicates that horizontal transfer of Wolbachia does not occur from host to wasp.     

Biological studies on two neotropical egg parasitoid species: Trichogramma nerudai and Trichogramma sp. (Hymenoptera: Trichogrammatidae)

The main biological attributes of two Neotropical egg parasitoids, the arrhenotokous Trichogramma nerudai and the thelytokous Trichogramma sp., were assessed under controlled laboratory conditions. Developmental time from egg to adult, and parasitoid survival, fecundity and fertility were studied using life tables. Results showed that T. nerudai had a faster developmental time than Trichogramma sp. (13.014±0.4019 and 13.595±0.4931 days, respectively). Both species showed similar life table statistics, r_m was 0.222 and 0.225 for T. nerudai and Trichogramma sp., respectively. Parasitoid survival averaged 95% for both species. The results obtained are discussed in the context of selecting one of these natural enemies as a potential biological control agent for the European pine shoot moth Rhyacionia buoliana (Lepidoptera: Tortricidae) in pine forests and the codling moth Cydia pomonella (Lepidoptera: Tortricidae) in apple orchards in Argentina.     

Trichogramma species (Hymenoptera: Trichogrammatidae) parasitoids of Lepidopteran eggs in Lara State, Venezuela

This work was conducted to determine the occurrence of Trichogramma wasp species in Lara State, Venezuela. Lepidopteran egg samples collected from various crop leaves were observed daily under laboratory conditions for emergence of Trichogramma species adult wasps. Trichogramma were also obtained from traps containing eggs from the hosts Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) and Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). In the laboratory, specimens of Trichogramma species were mounted on microscope slides to show male genitalia and other morphological characters used for its identification. Trichogramma atopovirilia Oatman y Platner emerged from S. frugiperda eggs collected in a cornfield at La Palomera, Humocaro Alto and at El Parchal, Humocaro Bajo, Municipio Morán. T. atopovirilia also emerged from S. frugiperda eggs collected in a cornfield at Sabana Grande and from S. cerealella eggs used as traps in a pepper culture at Tintinal, Municipio Andrés Eloy Blanco. T. exiguum Pinto y Platner emerged from S. frugiperda eggs used as traps or collected in cornfield at Totumito and at La Palomera, Humocaro Alto. T. pretiosum Riley emerged from Phthorimaea operculella Zeller eggs collected on stored potatoes at Monte Carmelo, Sanare. The identification of Trichogramma species in Lara State would be useful in the development of biological control programs for lepidopteran pests.     

Photoperiodic regulation of the diapause of the progeny in <Emphasis Type="Italic">Trichogramma embryophagum</Emphasis> Htg. (Hymenoptera,Trichogrammatidae): Dynamics of sensitivity to photoperiod at the immature stages of maternal females

Photoperiodic regulation of T. embryophagum progeny prepupal diapause was investigated under laboratory conditions. Maternal females developed at 20°C, the position of the photosensitive period was detected by transferring immature stages between the diapause-inducing “short” day (L:D = 12:12) and the diapause-averting “long” day (L:D = 20:4). Progeny generation developed at L:D = 12:12 under the near-threshold temperature of 13°, 14°, or 15°C. Experiments showed that, at least under the used photo-thermal regimens, only the pupal stage was sensitive to the photoperiod influence. The highest photosensitivity was recorded during the last two days before the adult emergence. In this critical period, even a single short day cycle induced diapause in most of individuals. However, the reaction to the long day was weaker: at least two long light days immediately preceding the maternal adult emergence were necessary to avert the diapause. If a short day was preceded by a long day by more than 2–3 days before the adult emergence, the stepwise photoperiodic response caused an increase in the tendency to diapause. The results of this study could be used in pest biocontrol practice for elaboration of optimal methods for Trichogramma mass rearing and storage and also for prediction of its seasonal cycles under natural conditions.     

Effect of insecticides on Trichogramma exiguum (Trichogrammatidae: Hymenoptera) preimaginal development and adult survival

The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.     

Pollen as a source of food for egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae)

The value of corn pollen as a food source for Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was assessed in the laboratory by testing the effect of different pollen diets on the longevity, capacity of parasitism and other life-table parameters. T. brassicae females that fed on corn pollen and water (wet filter paper dusted with pollen) lived significantly longer (4.97 days) than females that fed on water alone (2.67 days), but significantly shorter than those feeding on honey alone (8.37 days) or corn pollen and honey (8.23 days), respectively, in the absence of host eggs. The presence of European corn borer eggs (Ostrinia nubilalis Huebner, Lepidoptera: Pyralidae) significantly increased longevity. With host eggs available, female T. brassicae that fed on corn pollen and water lived significantly longer (4.9 days) than on water alone (2.60 days), but significantly shorter than on honey alone (12.33 days) or corn pollen and honey (12.17 days), respectively. The cumulative lifetime fecundity was 82.53 offspring pupae when fed on pollen and water, which was significantly higher than 61.70 for water alone but lower than feeding on honey alone (95.70) or corn pollen and honey (99.97), respectively. Compared to water alone, corn pollen and water increased the net reproduction rate (R₀), intrinsic rate of increase (r_m), and finite rate of increase (λ), and reduced the doubling time (T₂), but had no effects on the emergence rate, sex ratio, and mean generation time (T_c). In another set of experiments, 13 out of 30 females reduced the number of pollen grains offered to them. The average number of pollen grains utilized per female in this 48-h test 2.46±0.40 (mean±SE). Hence, T. brassicae used corn pollen as food that significantly increased longevity and fecundity of the tested females. Pollen and honey supplied a complete diet for T. brassicae, compared to pollen and water or water alone.     

Wolbachia在玉米螟赤眼蜂内的三重感染

Wolbachia是一类广泛存在于节肢动物体内的共生菌。玉米螟赤眼蜂Trichogramma ostriniae是我国玉米田间的优势赤眼蜂种, 据报道, 赤眼蜂种内有Wolbachia感染。本文利用Wolbachia的16s rDNA和wsp基因引物通过PCR方法对玉米螟赤眼蜂的野生种群进行了调查, 发现以wsp基因为鉴定依据, 检测的所有个体都感染了3种Wolbachia ［wOstGDAa (GenBank accession no. EU157103), wOstGDAb (GenBank accession no. EU157104) 和 wOstGDB (GenBank accession no. EU157105)］。本文首次报道了野生赤眼蜂种群内Wolbachia的三重感染率几乎为100%。根据本研究的结果, 可以推测当不同种赤眼蜂寄生同一寄主时, Wolbachia可能会在不同赤眼蜂种间进行横向传播。     

Naturally occurring egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) in a pomegranate orchard in Tunisia

Four Trichogramma species were found in a pomegranate orchard in Gabès, an arid region of Tunisia, from parasitized eggs of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae), an economically important insect pest. Identification based on assessment of male genitalia and internal transcribed spacer 2 ( ITS 2) sequences showed that they were T. bourarachae Pintureau and Babault, 1988, T. oleae Voegelé and Pointel, 1979, T. cacoeciae Marchal, 1927 and T. evanescens Westwood, 1833. Trichogramma evanescens is reported for the first time in Tunisia. Trichogramma cacoeciae was the largely dominant species in the analyzed samples, whereas T. bourarachae was present in a minor portion of 1.38%. The implications of these results for attempts at controlling E. ceratoniae are discussed.     

Strategic ejaculation in the egg parasitoid Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

Abstract.  1. Several parameters influence sperm allocation by males, including their size and sperm stock, intra-specific variability, quality of females', as well as the risk and intensity of sperm competition.
2. Models predict that males should invest the maximum ejaculate size when sperm competition intensity is low. As sperm competition intensity increases, males should decrease the number of sperm transferred during mating.
3. This decrease in sperm transfer to females occurs because the benefits gained by males with each extra unit of expenditure on sperm decrease. When sperm supply is not unlimited, males could expect a better return by keeping some or all sperm for mating under lower competition intensity.
4. In this study, the ejaculate size of males that were kept in groups of one, five or 10 males prior to mating, has been investigated in the haplodiploid egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae).
5. As predicted by theory, the number of sperm transferred decreased significantly with an increase in the number of rivals.
6. This is the first study showing strategic sperm allocation depending on sperm competition intensity in a parasitoid.     

繁育寄主对三种赤眼蜂个体大小及抱卵量的影响

【目的】繁育寄主及成蜂日龄均会影响赤眼蜂体内的抱卵量,为了解繁育寄主及育出赤眼蜂个体大小与赤眼蜂抱卵量的关系,我们在室内研究了米蛾 Corcyra cephalonica（Stainton）卵和亚洲玉米螟 Ostrinia furnacalis （Güenée）卵作为繁育寄主对3种赤眼蜂雌蜂大小、抱卵量的影响。【方法】在光周期14L:10D、温度25±1℃的室内条件下,以米蛾卵、亚洲玉米螟卵作为繁育寄主,解剖不同日龄（羽化后12-72 h）松毛虫赤眼蜂 Trichogramma dendrolimi Matsumura、玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen以及稻螟赤眼蜂Trichogramma japonicum Ashmead,观察雌蜂抱卵量,测量成蜂的大小,分析雌蜂抱卵量与其日龄、个体大小以及繁育寄主的关系【结果】在羽化后48 h以内,3种蜂的抱卵量随雌蜂日龄的增长而增加。羽化后72 h,除米蛾卵繁育的玉米螟赤眼蜂及玉米螟卵繁育的松毛虫赤眼蜂的抱卵量比羽化后48 h时略高外,其他组合均出现下降。以亚洲玉米螟卵为繁育寄主时的玉米螟赤眼蜂的抱卵量显著高于对应日龄的以米蛾卵为繁育寄主时的抱卵量,而松毛虫赤眼蜂（除羽化后12和24 h外）和稻螟赤眼蜂则相反;以米蛾卵为繁育寄主时,相同日龄的赤眼蜂中,松毛虫赤眼蜂抱卵量最高,稻螟赤眼蜂的抱卵量最低;以亚洲玉米螟卵为繁育寄主时,玉米螟赤眼蜂抱卵量最高,稻螟赤眼蜂抱卵量最低。雌蜂抱卵量与雌蜂个体大小呈线性正相关,相关程度随雌蜂日龄增加而更加明显。【结论】后足胫节长度可以作为评价松毛虫赤眼蜂、玉米螟赤眼蜂和稻螟赤眼蜂质量的指标。赤眼蜂抱卵量受繁育寄主、赤眼蜂蜂种及雌蜂日龄的显著影响,寄主的适合性也会影响育出赤眼蜂的大小,筛选合适的繁育寄主有助于提高赤眼蜂的质量。     

Effects of deltamethrin on the reproduction of Trichogramma cordubensis (Hymenoptera: Trichogrammatidae)

The influence of deltamethrin on the reproduction of Trichogramma cordubensis, a thelytokous egg parasitoid, was investigated by studying egg maturation and daily fecundity of insecticide treated wasps and offspring emergence rates. The insecticide was applied to the parasitoids at the prepupal stage within its host eggs (Ephestia kuehniella). The total number of parasitized eggs per female during the first 7 days was not significantly influenced by the tested concentrations of deltamethrin. Prevalence of parasitism during this period had a similar pattern between deltamethrin treatments and the control. In addition, the mean number of mature eggs observed per female per day was significantly correlated to mean daily fecundity, regardless of the treatments. Offspring emergence was significantly influenced by the insecticide treatments experienced on their progenitors, decreasing significantly at 48 and 72 h for the highest tested concentration of deltamethrin (23.6 mg [a.i.]/L). Despite that, deltamethrin had no adverse effects on the reproduction of treated wasps, particularly when was applied at the concentration recommended by the manufacturer (12.5 mg [a.i.]/L).     

Host-foraging success of three species of Trichogramma (Hymenoptera: Trichogrammatidae) in a simulated retail environment

Three species of trichogrammatid egg parasitoids (Trichogramma deion Pinto & Oatman, Trichogramma ostriniae Pang & Chen, and Trichogramma pretiosum Riley) (Hymenoptera: Trichogrammatidae) were evaluated under laboratory conditions as potential biological control agents for the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), on retail shelves. A single shelving unit was used in each trial and a grid of sentinel egg disks was used to evaluate foraging success. The shelving consisted of pallet units with five shelves that were either bare or stocked with empty cereal boxes. In each replicate, approximately 500 female Trichogramma were released at the center of the shelving unit and allowed to forage for 48 h. Percentage of egg parasitism and percentage of host egg mortality were recorded after 7 d. Foraging success as well as the spatial pattern of parasitism differed significantly among the three Trichogramma species. Percentage of egg parasitism was approximately 4 times greater for T. deion than for T. ostriniae or T. pretiosum. The vertical distribution of parasitism by T. deion was also more uniform than for the other two species. In addition, the presence of packaging affected the foraging efficiency of T. ostriniae and T. pretiosum but not T. deion. Based on these findings, Trichogramma deion may be the best-suited candidate for augmentative biological control of P. interpunctella in retail stores, and a central release point of T. deion will likely provide adequate coverage of products on pallet-type shelving.     

On the direct influence of photoperiod on diapause in <Emphasis Type="Italic">Trichogramma embryophagum</Emphasis> (Hymenoptera,Trichogrammatidae)

A direct photoperiodic reaction of T. embryophagum larvae was investigated in the laboratory. Maternal females developed at 20°C and day length of 12 h. Progeny generation developed at 14°C and day lengths of 0, 4, 8, 12, 16, 20, and 24 h. Experiments showed that under the short days (12, 8, and 4 h) and in continuous darkness, the percentage of diapausing individuals was significantly higher than under the long days of 16 and 20 h. Under permanent light, however, the inclination to diapause also increased. The earlier investigated maternal influence on T. embryophagum progeny diapause showed a somewhat different pattern of photoperiodic reaction. These results suggest that the direct effect of the day length on Trichogramma diapause is a relatively autonomous process rather than just a side-effect of the photoperiodic reaction determining maternal influence. However, this direct effect is very weak and could possibly be a “rudimentary reaction.”