Analysis of variations of handling-time inTrichogramma maidis

Variation in handling-time is studied in the association betweenTrichogramma maidis Pintureau & Vœgelé [Hym.: Trichogrammatidae] and one of its factitious hosts: the eggs of the Mediterranean flour mothEphestia kuehniella Zeller [Lep.: Pyralidae]. It is shown that the duration of egg laying behaviour decreases exponentially from the first host egg encountered onwards. This decreasing kinetic, which corresponds to a learning ability, shows a high variability between females, but a mother-daughter regression analysis fails to demonstrate any genetic transmissibility of this learning ability over 2 successive generations. Once the learning is over, there remains a residual variability which is, in part, under genetic control. The possible consequences of these results on the stability of host-parasite associations are discussed.      

Mise en évidence d'une activité kairomonale des œufs de la pyrale du maïs sur les femelles deTrichogramma maidis

Résumé Des extraits de la surface d'œufs de Pyrale du ma?s ont été testés en microenceinte et dans un olfactomètre linéaire sur des ♀♀ deTrichogramma maidis. En microenceinte, les extraits stimulent la locomotion et le comportement exploratoire des ♀♀. En olfactomètre ils stimulent à distance la remontée des tubes vers la source. Ces résultats impliquent la présence de substances à activité kairomonale sur les œufs de Pyrale du ma?s. Des analyses préliminaires des extraits ont été faites par chromatographie en phase gazeuse couplée ou non à la spectrométrie de masse et démontrent la présence de nombreux hydrocarbures.

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Summary Extracts from the surface of eggs of the European corn borer were tested in small observation chambers and in a linear olfactometer for their effects on the searching behaviour of the egg-parasitoidTrichogramma maidis. In the observation chambers, the extracts elicited exploratory behaviour by female parasitoids with no previous oviposition experiences and increased the time the females spent in walking and drumming their antennae. Recording the position of 10 ♀♀ each minute for 15 min in 2 tubes of an olfactometer, indicated that upwind motion was significantly greater in the tube containing 10 μl of an egg extract than in the control tube containing just solvent. It is concluded that kairomones are present onO. nubilalis eggs and could act as searching incitants and short-range attractants. Preliminary GC and GC/MS analysis revealed the abundance of hydrocarbons in the extracts but the active chemicals were not characterized.

     

Olfactory responses ofTrichogramma maidis Pint,et Voeg.: Effects of chemical cues and behavioral plasticity

Oriented responses of Trichogramma maidisPint, et Voeg. to airborne odors were observed in a four-armed olfactometer. Experiments were carried out with odors of host eggs, the sex pheromone of Ostrinia nubilalisHbn, and maize extract, offered singly or in combination, both to naive wasps and to wasps previously exposed to the tested odor during an oviposition experience. The exploratory behavior in the olfactometer was quantified by means of a computer program which performed a space-time analysis of the insect 's movements. Whereas the naive wasps did not respond to the odor of the eggs, the synthetic sex pheromone of O. nubilalis,or the maize extract presented singly, they did react to a mixture of these three volatile cues. Prior oviposition in the odor of maize extract or in the combination of odors induced an increased preference toward the conditioning scent. This phenomenon did not occur when the wasps were conditioned to egg odor or sex pheromone alone. These results suggest that females can learn to associate some olfactory cues with the presence of the host. Immediately following the presentation of the combination of odors, a strong attraction of experienced wasps occurred; it decreased as the experiment progressed and finally reached the level presented by naive insects. Adult conditioning to the combination of odors also resulted in reduced variability in the behavioral responses.     

Genetic variability in the reactive distance inTrichogramma brassicae after automatic tracking of the walking path

Efficiency of hymenopterous parasitoids to control pests in a biological control release program probably increases with increasing searching ability of the females, which, in return, likely depends on the distance from which females perceive their hosts (i.e., reactive distance). In this study, we first analyse this hypothesis with the help of a stochastic model simulating the walking path of isolatedTrichogramma females during their searching behaviour. Then, this reactive distance is estimated using automatic recording and analysis of the walking path of female wasps. Finally, the genetic variability for this trait is analysed in aTrichogramma brassicae Bezdenko (Hym.; Trichogrammatidae) population. Three types of hosts were used: Eggs ofEphestia kuehniella Zeller (Lep.; Pyralidae), eggs ofMamestra brassicae L. (Lep.; Noctuidae) and 0.45 mm glass beads.M. brassicae eggs are perceived from 4.01±0.15 mm, which is a significantly longer perceptive distance than forE. kuehniella eggs (3.69±0.10 mm) and glass beads (3.67±0.10 mm). Moreover, whatever the host tested, a significant genetic variation is observed in this trait in the population studied. The ecological and evolutionary implications and the agronomical importance of these results are discussed.     

Changes in host acceptance and host suitability as an effect of rearing Trichogramma maidis on a factitious host

Host acceptance and suitability of Ostrinia nubilalis Hbn. for Trichogramma maidis Pint. et Voeg. (Hymenoptera: Trichogrammatidae) were studied, after rearing the parasitoids on O. nubilalis or Ephestia kuehniella Oliv. (Lepidoptera: Pyralidae) for various numbers of generations. In cages, containing two maize plants with in total 30 egg masses of the natural host (O. nubilalis), wasps continuously reared on either E. kuehniella or O. nubilalis found egg masses in equal proportions. The former however, did not parasitize the eggs successfully, due to either low degree of host acceptance or insufficient host suitability or both. Subsequently, host acceptance behaviour of individual females from different strains was studied by means of direct observations after releasing them into a small arena containing eggs of O. nubilalis or E. kuehniella. Wasps continuously reared on O. nubilalis or 1–3 generations on E. kuehniella accepted egg masses of the natural host better than wasps continuously reared on E. kuehniella. Acceptance of O. nubilalis by the wasps gradually decreased with increasing numbers of generations reared on E. kuehniella. By rearing T. maidis, previously cultured on E. kuehniella, for five generations on O. nubilalis, acceptance of egg masses of this host species did not change. Host suitability of O. nubilalis appears to correspond with host acceptance of the strains. Contrary to the observations on O. nubilalis, acceptance and suitability of E. kuehniella were not influenced by the host on which T. maidis was reared. Results of this study show that host acceptance and suitability of the natural host are important quality factors for T. maidis when mass produced on a factitious host.

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Zusammenfassung Wirtsakzeptanz und Wirtseignung von Ostrinia nubilalis Hbn. für den Eiparasitoiden, Trichogramma maidis Pint. et. Voeg., wurden untersucht nach der Zucht auf dem natürlichen Wirt, O. nubilalis, oder auf dem Ersatzwirt, der Mehlmotte, Ephestia kühniella Zell.. Versuche mit Käfigen, in denen je zwei Maispflanzen mit insgesamt 30 Eigelegen von O. nubilalis und 40 Weibchen von T. maidis eingesperrt waren, zeigten, dass Weibchen, die seit über 150 Generationen auf O. nubilalis bzw. E. kühniella gezüchtet worden waren, die Eigelege gleich gut fanden. Während die auf O. nubilalis gezüchteten Parasitoide die Eigelege zu 80% parasitierten, war die Parasitierungsrate der auf E. kühniella gezüchteten Parasitoide gleich Null. Die Ursachen dieses Phänomens wurden in weiteren Versuchen durch direkte Beobachtungen über Wirtsakzeptanz und Wirtseignung untersucht. Einzelne Weibchen von Stämmen, die nur auf O. nubilalis oder während einer zunehmenden Generationenzahl auf E. kühniella gezüchtet worden waren, untersuchte man während 15 Minuten unter der Stereoskoplupe in einer kleinen Arena, die ein Eigelege des Maiszünslers oder Eier der Mehlmotte enthielt. Dabei zeigte sich, dass Wespen, die ausschliesslich auf Maiszünslereiern oder nur 1–3 Generationen auf Mehlmotteneiern gezüchtet worden waren, die Eigelege von O. nubilalis besser akzeptierten als solche, die seit vielen Generationen auf E. kühniella vermehrt worden waren. Die Wirtsakzeptanz verschlechterte sich mit zunehmender Generationenzahl auf E. kühniella. Wenn T. maidis nach 23 Generationen auf E. kühniella wieder während 5 Generationen auf O. nubilalis gezüchtet wurde, verbesserte sich die Akzeptanz der Eigelege von O. nubilalis nicht. Die Wirtseignung der Eigelege von O. nubilalis, stimmt überein mit der Wirtsakzeptanz der verschiedenen Stämme. Dies ergaben Versuche mit 15 Minuten Direktbeobachtung und bei 24 Stunden Expositionszeit. Im Gegensatz zu den Beobachtungen auf Eigelegen von O. nubilalis wurde die Akzeptanz und Eignung der Eier von E. kühniella durch die Zucht auf verschiedenen Wirten nicht beeinflusst. Das Ergebnis dieser Untersuchung zeigt, dass Akzeptanz und Eignung des natürlichen Wirtes wichtige Qualitätsfaktoren für T. maidis in der Massenzucht auf Ersatzwirten sind.

     

Trichogramma platneri (Hym.: Trichogrammatidae): Host choices between viable and nonviable codling moth,Cydia pomonella,and three-lined leafroller,Pandemis limitata (Lep.: Tortricidae) eggs

In laboratory host-preference studies,Trichogramma platneri Nagarkatti (Hym.: Trichogrammatidae) females, reared on viable codling moth,Cydia pomonella (L.) (Lep.: Tortricidae) eggs, parasitized significantly more viable than nonviable codling moth eggs produced by cobalt 60 irradiated adults. This ovipositional preference was maintained when competition increased per host egg. Similarly, one, three and fiveT. platneri females consistently oviposited more eggs into viable versus nonviable host eggs. A single femaleT. platneri parasitized a similar number of viableC. pomonella and three-lined leafroller,Pandemis limitata (Robinson) (Lep.: Tortricidae) eggs. However, as the number of females per host eggs increased, a significantly larger number of codling moth versus leafroller eggs were parasitized. One, three and fiveTrichogramma females parasitized significantly moreP. limitata versus nonviableC. pomonella eggs. NonviableC. pomonella eggs deflated to less than 25% of their original volume in four and ten days when held under dry and humid conditions respectively. The blackened prepupal stage of the parasitoid generally occurred in the nonviableC. pomonella eggs four days post-parasitization whereas the parasitized viable eggs blackened zero to one day earlier. Incubation under dry or humid conditions did not appear to influence the number of parasitized eggs that were able to blacken and show evidence of parasitism. Summerland Research Centre Contribution No. 938.     

Pathogenicity of fungal isolates (Ascomycota: Hypocreales) against Peregrinus maidis, Delphacodes kuscheli (Hemiptera: Delphacidae), and Dalbulus maidis (Hemiptera: Cicadellidae), vectors of corn diseases

Preliminary screening assays were carried out on 17 isolates from five fungal species Beauveria bassiana, Lecanicillium muscarium, Metarhizium anisopliae, Isaria farinosa, and I. fumosorosea. The three most effective isolates against Peregrinus maidis (Hemiptera: Delphacidae) were B. bassiana CEP 147, CEP 150, and CEP 189. There were no consistent differences found in males and females regarding fungal susceptibility. However, more females than males were proportionally infected. There was not a correlation between the percentage of conidial germination and the percentage of mortality caused by fungal infection in any of the treatments. Only B. bassiana CEP 147, which caused a cumulative mortality of 69.8 ± 6.4% after 7 days post-inoculation, was selected to be assayed against adults of P. maidis, Delphacodes kuscheli (Hemiptera: Delphacidae), and Dalbulus maidis (Hemiptera: Cicadellidae). In pathogenicity tests significant differences were observed among treatments. After 2 weeks post-inoculation, both D. kuscheli (cumulative mortality of 73.3 ± 9.0%) and P. maidis (cumulative mortality of 68.6 ± 6.7%) were significantly more susceptible than D. maidis (cumulative mortality of 49.9 ± 9.7%) to the selected isolate.     

Variation in locomotion between laboratory strains of Trichogramma maidis and its impact on parasitism of eggs of Ostrinia nubilalis in the field

The locomotion of females of different strains of the parasitic wasp Trichogramma maidis (Hymenoptera, Trichogrammatidae) was measured under standardized conditions and compared to their efficiency in the field for several years. A manual and an automatic method for recording and analysing the locomotion of insects are described and results for differently reared laboratory strains of T. maidis are presented. The correlation between manual and automatic measurements of the travel speed was significant (r=0.999). The automatic method was developed by means of an Image Processing System. T. maidis females were individually released in an arena, and the walking tracks were recorded by a video camera. To reconstruct the real path, a mathematical model which gives highly accurate path length estimations — termed arcus interpolation — was used. Furthermore the same programme permits the calculation of parameters like turning rate and angles, the activity pattern over the whole observation period or for selected parts of it. The locomotion of different T. maidis strains in the laboratory was compared with their efficiency in the field. An obvious relation between locomotion and parasitization in the field was apparent. The probability for parasitism of Ostrinia nubilalis Hbn. (Lepidoptera, Pyralidae) egg batches decreased linearly with increasing distance from the release point of Trichogramma wasps. The travel speed of the females of different T. maidis strains was found to be positively related to the potential for parasitism in the field. The travel speed can therefore be used as a parameter to estimate the capacity for host location and the efficiency of a T. maidis strain for inundative biological control programmes.

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Zusammenfassung Während mehrerer Jahre wurde die im Labor bestimmte Laufgeschwindigkeit von Trichogramma maidis Pint. & Voeg. (Hymenoptera, Trichogrammatidae) mit ihrem Parasitierungspotential im Freiland verglichen. Für die Bestimmung der Bewegungsaktivität von T. maidis werden zwei Methoden beschrieben. Mit der einen wird die zurückgelegte Wegstrecke eines Insekts, während einer definierten Zeitperiode, mit einem Planimeter gemessen. Für die zweite, automatische Bestimmung der Bewegungsaktivität verwendete man einen IPS (Image Processing System von KONTRON München), für welches entsprechende Programme entwickelt wurden. Bei der zweiten Messmethode wird der Weg jedes einzelnen Tieres in einer Laufarena von 24 mm Durchmesser während 10 Min mit einer Videokamera aufgenommen. Jede Sekunde werden die Schwerpunktskoordinaten des Tieres bestimmt. Die Länge des zurückgelegten Weges der Tiere wurde mit Hilfe eines Berechnungsmodells geschätzt. Die Wegstreckenkorrektur erfolgte mit Kreisbögen, welche aus drei aufeinanderfolgenden Punkten jedes Wegabschnittes berechnet werden. Mit dieser Korrektur konnte auf einfache Weise eine sehr genaue Schätzung der Laufstrecke erzielt werden. Die Ergebnisse der beiden Methoden weisen eine enge Korrelation (r=0.999) auf. Mit dem entwickelten Programm lassen sich zusätzlich, zu den effektiven Laufstrecken, auch noch Anzahl und Stärke der Richtungsänderungen sowie das Aktivitätsmuster der ganzen Beobachtungsperiode bestimmen.Die Untersuchungen ergaben, dass die Parasitierungsrate der Eigelege von Ostrinia nubilalis Hb. (Pyralidae, Lepidoptera) mit zunehmender Distanz vom Freilassungspunkt von T. maidis abnahm. Die Wahrscheinlichkeit für O. nubilalis-Gelege parasitiert zu werden, kann innerhalb der ersten 8 m am besten mit einem linearen Modell beschrieben werden. Das Parasitierungspotential definierte man als Integral der Parasitierungs-Wahrscheinlichkeit für O. nubilalis-Gelege über die Distanz vom Freilassungspunkt weg. Es zeigte sich, dass zwischen den im Labor bestimmten Laufgeschwindigkeiten der verschiedenen T. maidis Stämme und den im Feld gemessenen Parasitierungspotentiale eine positive Beziehung besteht. Die Laufgeschwindigkeit von T. maidis Weibchen kann somit als ein Parameter zur Bestimmung der Suchkapazität eines Trichogramma Stammes und in etablierten Bekämpfungsprogrammen als Eignungstest der Provenienzen für die biologische Bekämpfung betrachtet werden. Laufgeschwindigkeits-Bestimmungen ermöglichen es, rasche und ökonomische Qualitätskontrollen von in Massen gezüchteten T. maidis vorzunehmen, indem bereits im Labor die Eignung der T. maidis Stämmen für die Bekämpfung von O. nubilalis beurteilt werden kann.

     

Sensory receptors of the ovipositor ofTrichogramma maidis [Hym.:Trichogrammatidae]

Sensory receptors of the ovipositor ofTrichogramma maidis are described. Sense organs are found on the 2^nd valvifers (1 type), on the tip of the 3^rd valvulae (2 types) and on the 1^st valvulae (4 types). The nature and possible functions of these sensilla are discussed.      

Host Preferences of Trichogramma pretiosum and the Influence of Prior Ovipositional Experience on the Parasitism of Plutella xylostella and Pseudoplusia includens Eggs

Trichogramma wasps are generalist egg parasitoids used in biological control efforts. In a multi host situation they may preferentially parasitize a non-target host species to the detriment of the control program. Plutella xylostella Linnaeus (Lepidoptera: Plutellidae) is a very serious pest of cabbage, but is only one in a number of species in the ‘cabbageworm’ complex. We investigated the host preferences of Trichogramma pretiosum Riley (Hymenoptera: Chalcidoidea) when offered the eggs of Plutella xylostella and the eggs of Pseudoplusia includens Hübner (Lepidoptera: Noctuidae), another species in the ‘cabbageworm’ complex. Trichogramma pretiosum reared on the eggs of the factitious host Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) parasitized both Plutella xylostella and Pseudoplusia includens eggs under laboratory conditions. For both choice and no-choice experiments, T. pretiosum parasitized significantly more P. xylostella eggs than P. includens eggs. Prior ovipositional experience with one or other of the two host species had no effect on the subsequent parasitism levels of the two host species. The preference for P. xylostella eggs was also not affected by this prior ovipositional experience.     

The size of the female and quality assessment of mass-rearedTrichogramma spp.

The relationship between the index of female's size, hind tibia length (HTL), and selected fitness parameters used in quality assessment of mass-rearedTrichogramma spp. (Hymenoptera, Trichogrammatidae) was investigated. The studied fitness parameters were: the number of mature eggs present in the ovaries of females 0–2 hours, as well as 1, 2 and 3 days old, lifetime fecundity, fecundity during a 24 h period, longevity in the presence and absence of the factitious host (Ephestia kuehniella Zeller) and locomotor activity. The relationship between HTL and fitness parameters was analysed in 7 strains ofTrichogramma spp. (Trichogramma dendrolimi Matsumura,T. evanecens Westwood,T. maidis Pinturea et Voegelé andT. ostriniae Pang et Chen) using linear correlation. No significant relationship was found between HTL and egg complement, fecundity, longevity and locomotor activity. The results indicate that HTL used as an index of female's size is not suitable for quality assessment ofTrichogramma reared onE. kuehnieIla.     

Is the parasitization capacity of Trichogramma cordubensis influenced by the age of the females?

We investigated the parasitization capacity of Trichogramma cordubensis Vargas & Cabello (Hymenoptera: Trichogrammatidae) females aged 24 h, 48 h, 72 h, 96 h, 120 h, and 144 h, using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as hosts. Wasps were held without hosts during the period of ageing, therefore being increasingly time-limited with respect to parasitization as they got older. The total number of parasitized hosts decreased as the age of the parasitoid increased. However, the proportion of lifetime parasitism carried out on the first day increased with wasp age, up to 120-h old females. These results show that the parasitization capacity of ageing T. cordubensis females changes as they become time-limited. The consequences of such changes for biological control programs are discussed.     

Acceptability and suitability of Tuta absoluta eggs from irradiated parents to parasitism by Trichogramma nerudai and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

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Flight initiation in the egg parasitoid Trichogramma minutum: Effects of ambient temperature, mates, food, and host eggs

Emergence, preening, and flight initiation were studied in laboratory-reared Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). Male parasitoids emerged first and flew before females. When both sexes were present in flight cylinders, female parasitoids flew before males. Flight propensity in males was negatively related to the number of emerging females, while flight propensity in females was independent of the number of males present. Ambient temperature significantly affected the propensity and timing of flight; between 70–80% of the parasitoids flew at 25 and 30 °C while less than 4%, mostly males, flew at 20 °C. No flights were observed at 15 °C. The presence of fresh host eggs caused a reduction in the proportion of female parasitoids that flew and a delay in the time to flight for the females that did fly. The presence of food increased the flight propensity of female parasitoids, but did not affect the timing of flight. The relationship between flight behaviour and the efficiency of mass-reared Trichogramma is discussed in terms of its importance for inundative release programmes.     

Caractérisation enzymatique deTrichogramma evanescens et deT. Maidis [Hym.: Trichogrammatidae]; Étude des hybrides

Résumé Trois systèmes enzymatiques (estérases, MDH et tétrazolium-oxydases) ont été étudiés par électrophorèse chez 2 espèces jumelles de trichogrammes:Trichogramma evanescens Westwood etT. maidis Pintureau & Voegelé. Les estérases et les MDH permettent de caractériser les souches de ces espèces en élevage à Antibes. Les estérases des hybrides interspécifiques F₁ et F₂ ont également été tudiées. Elles ont permis de confirmer qu'un phénomène d'induction de la parthénogénèse thélytoque appara?t chez certaines femelles.

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Summary Three enzymatic systems (esterases, malate-dehydrogenases and tetrazolium-oxydases) were studied by electrophoresis in two sibling species ofTrichogramma: T. evanescens Westwood andT. maidis Pintureau & Voegelé. The esterases and the MDH allow to characterize the strains of these species in rearing in Antibes. The esterases of interspecific hybríds F₁ and F₂ were studied too. They allow to confirm that a phenomenon of induction of thelytoky occurs in some females.

     

The use of oviposition‐induced plant cues by Trichogramma egg parasitoids

1. Female parasitoids have evolved various foraging strategies in order to find suitable hosts. Egg parasitoids have been shown to exploit plant cues induced by the deposition of host eggs. 2. The tiny wasp Trichogramma brassicae uses oviposition‐induced cues from Brussels sprouts to locate eggs of the cabbage white butterflies Pieris brassicae and Pieris rapae that differ in their egg‐laying behaviour. These plant cues are elicited by male‐derived anti‐aphrodisiac pheromones in the accessory reproductive gland (ARG) secretions of mated female butterflies. However, the closely related generalist species Trichogramma evanescens does not respond to Brussels sprout cues induced by the deposition of P. brassicae egg clutches. 3. Here we showed in two‐choice bioassays that T. evanescens wasps respond to Brussels sprout cues induced by (i) the deposition of single eggs by P. rapae, and (ii) the application of ARG secretions from either mated P. rapae females, or from virgin female butterflies in combination with P. rapae's anti‐aphrodisiac compound indole. The wasps only associatively learned to respond to Brussels sprout cues after applying indole alone by linking those cues with the presence of P. rapae eggs. 4. Our results indicate that Trichogramma wasps more commonly exploit oviposition‐induced plant cues to locate their host eggs. Generalist wasps show less specificity in their response than specialists and employ associative learning.     

Nocturnal parasitism of moth eggs by Trichogramma wasps

Parasitoid wasps of the genus Trichogramma are used worldwide as biological control agents against lepidopteran pests. Trichogramma wasps develop inside eggs of a wide range of host species, most of them moths. They are generally considered as diurnal insects. Here, we investigated whether Trichogramma wasps can also successfully parasitise host eggs at night under controlled laboratory conditions. Eggs of the moth Ephestia kuehniella were offered under dark conditions (scotophase) to females of Trichogramma brassicae and Trichogramma evanescens either from 9:00 PM to 9:00 AM or from 11:00 AM to 5:00 PM at four different temperatures (5°C, 10°C, 15°C and 20°C). Both species are known to parasitise E. kuehniella eggs in the photophase during daytime. The results show that T. brassicae did not parasitise eggs in the scotophase at night and only very few in the artificially induced scotophase during daytime from 10°C to 20°C. In contrast, T. evanescens parasitised more eggs in the dark both at night and artificially induced scotophase during daytime. Parasitism in the scotophase already started at 5°C, with more eggs being parasitised and more offspring being produced at higher temperatures. T. evanescens displayed higher parasitism activity in the induced scotophase during daytime than in the scotophase at night. The present study suggests that Trichogramma are capable of successfully parasitising host eggs at night, even at low temperatures, but that nocturnal activity with respect to parasitism varies between wasp species.     

Oviposition behavior of Edovum puttleri, reared on two hosts, Leptinotarsa decemlineata and L. texana

Female Edovum puttleri Grissell [Hymenoptera: Eulophidae], reared from eggs of Leptinotarsa decemlineata (Say) or Leptinotarsa texana Schaeffer [Coleoptera: Chrysomelidae], were videotaped as they attacked egg masses of L. decemlineata containing 20 host eggs. We identified 15 components of ovipositional behavior. Parasitoids reared on L. texana attacked and oviposited in significantly more host eggs than did females reared on L. decemlineata. Ethometric analyses of behavioral transitions and a clustering analysis of 34 behavioral parameters showed that females reared on L. texana attacked the host egg mass in a different manner than those reared from L. decemlineata. It was concluded that differences were associated with the host species upon which they were reared. Contrary to previous reports, mortality of unparasitized hosts was caused by an ovipositor probe of short duration, which was not related to host-feeding.     

Development ofTrichogramma brasiliensis [Hym: Trichogrammatidae] on eggs of radiation sterilized females of potato tuberworm,Phthorimaea operculella [Lep.: Gelechiidae]

Trichogramma brasiliensis (Ashmead) could be successfully reared on the eggs laid by gamma-irradiated sterile ♀ of the potato tuberworm,Phthorimaea operculella Zeller. Even after rearing 10 generations of the parasitoid on such eggs there were no adverse effects on various developmental parameters.