Larval Frass Research Articles

Effects of learning experience on behaviour of the generalist parasitoid Sclerodermus pupariae to novel hosts

AbstractMassicus raddei Blessig (Coleoptera: Cerambycidae), also referred to as the oak long‐horned beetle (OLB), is a non‐natural host for the generalist parasitoid Sclerodermus pupariae Yang et Yao (Hymenoptera: Bethylidae). To determine whether this generalist parasitoid might be a suitable agent for the control of OLB, the adaptive learning experience of adult female parasitoids to OLB larvae was investigated in the laboratory. A Y‐tube olfactometer bioassay was used to examine the effects of adaptive learning experience on the foraging ability of parasitoids for OLB larvae. The results indicated that parasitoids were significantly attracted by the volatiles of ash bark, Fraxinus velutina, with emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) larvae and larval frass, after exposure to ash bark mixed with EAB larval frass (learning condition A). In contrast, after exposure to oak bark, Quercus liaotungensis, mixed with OLB larval frass (learning condition C), parasitoids showed significant preference for the volatiles of oak bark with OLB larvae and larval frass. On the basis of the results of no‐choice tests, we found that parasitoids exposed to learning condition C had greater paralysis efficiency and higher OLB larvae parasitism rates than those exposed to learning condition A or no experience. Furthermore, parasitoids fed on OLB larvae in learning condition C had significantly greater paralysis efficiency and higher OLB larvae parasitism rates than other parasitoids tested. Parasitoids fed on EAB larvae in learning condition A had the lowest paralysis efficiency and OLB larvae parasitism rates among the parasitoids tested. These findings suggested that adaptive learning significantly enhanced the ability of a generalist parasitoid to utilize a novel host. This may provide a new approach to controlling non‐natural hosts using generalist parasitoids.

Characterization and virulence of Beauveria spp. recovered from emerald ash borer in southwestern Ontario, Canada

The emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), is an invasive wood boring beetle that is decimating North America’s ash trees (Fraxinus spp.). To find effective and safe indigenous biocontrol agents to manage EAB, we conducted a survey in 2008–2009 of entomopathogenic fungi (EPF) infecting EAB in five outbreak sites in southwestern Ontario, Canada. A total of 78 Beauveria spp. isolates were retrieved from dead and mycosed EAB cadavers residing in the phloem tissues of dead ash barks, larval frass extracted from feeding galleries under the bark of dead trees. Molecular characterization using sequences of the ITS, 5′ end of EF1-α and intergenic Bloc region fragments revealed that Beauveria bassiana and Beauveria pseudobassiana were commonly associated with EAB in the sampled sites. Based on phylogenetic analysis inferred from ITS sequences, 17 of these isolates clustered with B. bassiana, which further grouped into three different sub-clades. However, the combined EF1-α and Bloc sequences detected five genotypes among the three sub-clades. The remaining 61 isolates clustered with B. pseudobassiana, which had identical ITS sequences but were further subdivided into two genotypes by variation in the EF1-α and Bloc regions. Initial virulence screening against EAB adults of 23 isolates representing the different clades yielded 8 that produced more than 90% mortality in a single concentration assay. These isolates differed in virulence based on LC50 values estimated from multiple concentration bioassay and based on mean survival times at a conidia concentration of 2×106 conidia/ml. B. bassiana isolate L49-1AA was significantly more virulent and produced more conidia on EAB cadavers compared to the other indigenous isolates and the commercial strain B. bassiana GHA suggesting that L49-1AA may have potential as a microbiological control agent against EAB.

Associations of yeasts with spotted-wing Drosophila (Drosophila suzukii; Diptera: Drosophilidae) in cherries and raspberries.

A rich history of investigation documents various Drosophila-yeast mutualisms, suggesting that Drosophila suzukii similarly has an association with a specific yeast species or community. To discover candidate yeast species, yeasts were isolated from larval frass, adult midguts, and fruit hosts of D. suzukii. Terminal restriction fragment length polymorphism (TRFLP) technology and decimal dilution plating were used to identify and determine the relative abundance of yeast species present in fruit juice samples that were either infested with D. suzukii or not infested. Yeasts were less abundant in uninfested than infested samples. A total of 126 independent yeast isolates were cultivated from frass, midguts, and fruit hosts of D. suzukii, representing 28 species of yeasts, with Hanseniaspora uvarum predominating. This suggests an association between D. suzukii and H. uvarum that could be utilized for pest management of the highly pestiferous D. suzukii.

Midgut and Fat Body Bacteriocytes in Neotropical Cerambycid Beetles (Coleoptera: Cerambycidae)

Xylophagous insects derive nutrients from intractable substrates by producing or ingesting cellulolytic enzymes, or by maintaining associations with symbiotic microbes. Wood-boring cerambycid beetle larvae sometimes house maternally-transmitted endosymbiotic yeasts that are presumed to provide their hosts with nutritional benefits. These are thought to be absent from species in the large subfamily Lamiinae; nevertheless yeasts have been repeatedly isolated from the guts of neotropical lamiines. The objective of this study was to conduct transmission electron microscopy (TEM) studies of cerambycid larval midgut tissues to determine if gut yeasts were intracellular, or simply present in the gut lumen. Nine cerambycid larvae were harvested from two trees in the Brazil nut family (Lecythidaceae) in the rain forest of SE Peru; seven were identified using mtDNA sequence data and processed for TEM. Yeasts cultured from larval frass or exuvia, and identified with rDNA sequence data, were identical or similar to yeasts previously isolated from beetles. In TEM analyses yeast cells were found only in the gut lumens, sometimes associated with fragments of thick-walled xylem cells. Apparent bacteriocytes were found in either midgut or fat body tissue of three larval specimens, including two lamiines. This is the first report of a potential fat body symbiosis in a cerambycid beetle. Future studies of cerambycid symbiosis should distinguish the identities and potential roles of free-living organisms in the gut lumen from those of organisms harbored within gut epithelial or fat body tissue.

Olfactory response of Dastarcus helophoroides (Coleoptera: Bothrideridae) to larval frass of Anoplophora glabripennis (Coleoptera: Cerambycidae) on different host tree species

The Asian longhorned beetle, Anoplophora glabripennis, is a destructive pest that attacks many species of deciduous hardwood trees. One of its natural enemies is Dastarcus helophoroides that parasitizes many species of longhorned beetles. Larval frass from six different host tree species varied in attraction to D. helophoroides adults, and frass from one host species, Acer negundo, showed no attraction at all. This information has practical benefits to evaluating the efficacy of D. helophoroides as a biological control agent for A. glabripennis and increases our understanding of the co-evolution between this parasitoid, its host, and host food trees.

Electrophysiological Response of Female Dogwood Borer (Lepidoptera: Sesiidae) to Volatile Compounds from Apple Trees

Coupled gas chromatography and electroantennogram detection (GC-EAD) analyses of headspace volatiles from apple host tissues revealed a total of 16 compounds to which female dogwood borer, Synanthedon scitula (Harris), antennae responded. There were no differences in the amplitude of the response of antennae from virgin and mated females, and no consistent responses to host odors were generated from male antennae. Four compounds, including octanal, nonanal, decanal, and methyl salicylate, were identified from all headspace collections taken from apple trees. Use of the solid-phase microextraction (SPME) technique revealed that a single volatile compound, α-bergamotene, emanating from larval dogwood borer frass elicited a strong female antennal response. This compound was also present in headspace collections from ‘Red Chief Delicious’ apple trees with burr knot tissue infested with dogwood borer larvae and from 1-d-old cut bark on ‘Granny Smith’ trees, suggesting that it is produced by apple trees in resp...

Electroantennogram and behavioral responses of Pteromalus cerealellae to odor stimuli associated with its host, Callosobruchus maculatus

Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is a generalist parasitoid of the larvae of many stored-product insects, including the cowpea seed beetle, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), which live endophytically in cowpea seeds. The role of host-related semiochemicals in the host location behavior of this parasitoid was investigated using electroantennogram (EAG) and behavioral (olfactometer) techniques. Responses of mated and unmated female P. cerealellae were tested to a variety of host-related chemical stimuli including hexane extracts of uninfested cowpea seeds, (bruchid)-infested cowpea seeds, bruchid larvae (whole body or WB), larval frass, adult female bruchids (WB), and adult male bruchids (WB). All of the tested stimuli elicited significant EAG responses in unmated and mated female P. cerealellae, with mated females exhibiting a greater EAG response than unmated females to some treatments. Results from Y-tube olfactometer bioassays demonstrated a significant response of mated female P. cerealellae to extracts of uninfested cowpea seeds, infested cowpea seeds, adult female bruchids, bruchid larvae, and larval frass, but no significant response was elicited by the extract of adult male bruchids. Pair-wise comparisons of the four most attractive stimuli (i.e. uninfested seeds, infested seeds, bruchid larvae, and larval frass) in a four-way olfactometer showed preference of mated female P. cerealellae for the extract of uninfested cowpea seeds compared to larval frass extract. No significant differences were recorded between other paired treatments. These results suggest the relative importance of volatile cues from seeds (host habitat) in mediating host location by P. cerealellae.

The Role of Frass and Cocoon Volatiles in Host Location by Monodontomerus aeneus, a Parasitoid of Megachilid Solitary Bees

Monodontomerus aeneus (Fonscolombe) is a parasitic wasp that oviposits on the prepupae and pupae of Osmia cornuta (Latreille) and other solitary bee species. A two-armed olfactometer was used to test the olfactory attractiveness of O. cornuta prepupae, cocoon, and larval frass to female M. aeneus. Both cocoon and frass attracted the female parasitoids, but frass alone was more attractive than the cocoon and the cocoon with frass was more attractive than frass alone. Female parasitoids were not attracted by the host prepupa. M33 (methanol) was the organic volatile most emitted by cocoons and m61 (acetic acid) was the compound most emitted by frass. However, cocoons showed higher emission for almost all compounds, including m61 (acetic acid). Although acetic acid alone attracted M. aeneus, a complex volatile signal is probably involved in the attraction process because the ratio of acetic acid and acetaldehyde characteristic of the frass was more attractive than other ratios.

Biomonitoring seasonal changes in the environmental impact of atmospheric pollution around junction 16 of the M25 London Orbital Motorway (a high traffic area), United Kingdom

Larvae of a lichenophagous bagworm moth, Luffia ferchaultella [Stephens 1850], were used to monitor the potential environmental impact of pollutants from a diffuse emission source, exhaust emission products, around Junction 16 of the M25 London Orbital motorway where it interchanges with the M40 motorway. Larvae were fed terrestrial epiphytic algae, collected on four occasions over a 3.5-year period, from 17 sites located within a 16 km(2) survey area. After 10 days of exposure to algae from certain sites, large reductions in the amount of fecal material (frass) produced by the larvae were noted. These reductions correlated with the concentrations of exhaust-related metals in the algae. On all four sampling occasions one site, located close to the junction, had some of the highest levels of exhaust related contaminants and resulted in significantly reduced larval frass production. Geostatistics were used to map the extent of the affected areas. On all four sampling occasions sites located down wind, to the east of the interchange, were statistically significantly affected. This area of impact increased in extent from 1998 to 2000, when a second area of contamination developed to the south west of the junction. By January 2001 the extent of the impacted area in the south west of Junction 16 had increased, while that to the east had declined. By September 2001 the extent of the impacted area to the west of the junction had spread still further, while the impacted area to the east remained reduced when compared with the situation found in 1998.

Parasitism and olfactory responses of Dastarcus helophoroides (Coleoptera: Bothrideridae) to different Cerambycid hosts

Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) is an important natural enemy of longhorned beetles (Coleoptera: Cerambycidae). It is distributed throughout most Provinces in China. We investigated whether there were differences among D. helophoroides populations collected from different hosts in different geographic locations. Results showed that different D. helophoroides populations displayed different olfactory responses to larval frass from different longhorned beetle species. All populations were significantly attracted to the frass of their original hosts. Parasitism rates of different populations also varied when supplied with host larvae of the same longhorned beetle species. These results indicate that the three D. helophoroides populations tested differed in host-related behaviors. Therefore, the population of D. helophoroides must be taken into consideration when implementing biological control programs for different species of longhorned beetle.

(R)‐(+)‐limonene, kairomone for Dastarcus helophoroides, a natural enemy of longhorned beetles

Abstract1 Chemical cues involved in host location by Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae), a parasitoid of Anoplophora glabripennis Motschulsky, Monochamus alternatus Hope, Massicus raddei (Blessig), Apriona germari (Hope), Apriona swainsoni (Hope) and Batocera horsfielde (Hope) in the family Cerambycidae, were investigated in a Y‐tube olfactometer. Responses of D. helophoroides adults toward odour sources from their host (M. raddei) and host tree (Quercus mongolicus Fisch. ex. Turcz.) were tested in either no‐choice or two‐way choice tests. Wood with larval tunnels and larvae frass were attractive to D. helophoroides. Both sexes showed attraction to wood with larval tunnels.2 Volatile chemicals emitted from wood with larval tunnels and larval frass were collected on Porapak Q and analyzed by gas chromatography‐mass spectrometry. Several compounds identified from these sources, including α‐pinene, β‐pinene, Δ‐3‐carene, limonene and β‐myrcene, were tested against D. helophoroides in the same Y‐tube olfactometer.3 The result showed that D. helophoroides adults were attracted to (R)‐(+)‐limonene, with or without the background odour from uninfested fresh wood. This may suggest that (R)‐(+)‐limonene is an important kairomone for this parasitic beetle.4 Dose‐dependent response of D. helophoroides adults to (R)‐(+)‐limonene indicated that D. helophoroides adults showed significant attraction to (R)‐(+)‐limonene when release rates exceeded 2.08 μg/h in Y‐tube olfactometer tests. Moreover, significantly more A. glabripennis larvae were parasitized by D. helophoroides in the presence of R‐(+)‐limonene, relative to the control in cage experiments.

Kairomone traps: a tool for monitoring the invasive spruce bark beetle Dendroctonus micans (Coleoptera: Scolytinae) and its specific predator, Rhizophagus grandis (Coleoptera: Monotomidae)

Summary The Eurasian spruce bark beetle Dendroctonus micans is a major pest of spruce which is expanding its range in France, Turkey, England and Wales. Its monospecific predator Rhizophagus grandis has followed its prey naturally into most areas and since the 1960s has also been mass‐produced and released within newly infested locations. Assessing bark‐beetle presence at previously uninfested sites, or predator establishment after release or natural spread, currently depends on direct observation of D. micans brood chambers. This is a slow and unreliable process because bark‐beetle attacks are solitary, cryptic and occur on living trees. An effective trapping method would thus be most useful. A synthetic lure for R. grandis was first field‐tested in release–recapture experiments. Release points were surrounded by one or two concentric rings of traps baited with either D. micans larval frass or with a blend of synthetic chemicals. Kairomone‐trapping using the synthetic lure was then tested in the field, monitoring R. grandis in 58 spruce stands in Belgium and France. In the release–recapture experiments, up to 65% of the released predators were caught within 48 h. Catches with the synthetic lure and with prey frass were not significantly different. Field‐trapping assays showed R. grandis establishment in 30 stands, including areas where the predator had been introduced artificially. Trapping was unsuccessful at the southern and western limits of D. micans’ range. Combined visual and trapping approaches identified 32 stands containing the predators, with two false negatives with the trapping method, compared to 19 for the visual surveys. Unexpectedly, male and female D. micans adults were trapped in some cases. The combined approach identified 43 attacked stands, among which there were four false negatives with the trapping method and 11 with the visual surveys. Synthesis and applications. To our knowledge, this is one of the first cases of using kairomone traps to monitor a predator after releases for biocontrol. Furthermore, because this predator is strictly prey‐specific, this technique also identifies stands colonized by D. micans bark beetles. Following inoculative predator releases, kairomone trapping could be used to survey for D. micans in areas under colonization or in European Union ‘Protected Zones’.

Kairomones Extracted from Rice Yellow Stem Borer and their Influence on Egg Parasitization by Trichogramma japonicum Ashmead

Host location and acceptance by egg parasitoids can be mediated by close-range host stimuli. In this study, we tested the response of Trichogramma japonicum Ashmead to cuticular extracts of adult and larval rice yellow stem borer (YSB), Scripophaga incertulas Walker. We also studied the wasps' response to extracts from YSB larval frass. Laboratory bioassays revealed that hexane extracts of the adult host body stimulate ovipositor probing of T. japonicum. Extracts of larval frass also stimulated parasitization. In contrast, host larval cuticular extracts had no effect on parasitization rates. Fractionation of the crude extracts of adult YSB cuticular extracts was performed using silica gel chromatography, followed by bioassays of the individual fractions to test their effects on wasp behavior. Analyses of the most active fractions by gas chromatography-mass spectrometry revealed that the extract contained saturated long chain alkanes and alkenes, with carbon numbers ranging from C20 to C32. Hydrocarbons were applied onto host eggs to test their effects on parasitization rates. Treatments of eggs with docosane, tetracosane, pentacosane, and eicosane enhanced host egg parasitization, while pentadecane, hexadecane, and nonadecane deterred oviposition.

Attraction of Dibrachys cavus (Hymenoptera: Pteromalidae) to its Host Frass Volatiles

The European grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae), is a polyphagous insect able to develop on grapes and wild plants. We tested the hypothesis that the parasitoid Dibrachys cavus (Hymenoptera: Pteromalidae) uses the larval frass in its host search. A two-armed olfactometer was used to measure the attractiveness of L. botrana larvae, their silk, or their frass after larvae were fed on different host plants. Frass of three Lepidoptera (L. botrana, Eupoecillia ambiguella, Sphinx ligustri) and one Orthoptera (Chorthippus brunneus) was assayed, but only L. botrana was used to test an effect of the larval host plant (two grape cultivars and three other plant species) to D. cavus females. Larvae without frass did not attract D. cavus whatever their origin, but their frass was attractive at a dose of 2-3 days equivalent of larval frass production. The silk produced by a single larva (L. botrana) was not attractive to D. cavus. The parasitoid was most attracted to the odor of S. ligustri; the frass of L. botrana was more attractive than that of E. ambiguella, irrespective of the species on which D. cavus had been reared. There was no difference in attractiveness of frass collected from L. botrana raised on food containing different plants. Chemical extracts using five different polarity solvents (acetone, dichloromethane, hexane, methanol, and water) differed in attractiveness to D. cavus. Water and dichloromethane were the most attractive. This suggests that a complex volatile signal made from intermediate to polar volatiles may be involved in attraction. D. cavus used frass to discriminate between different potential host species. Our results revealed that the larval food of L. botrana did not modify frass attractiveness, but that the moth species did.

Using nutritional indices to study LOX3‐dependent insect resistance

Induced resistance to biotic attackers is thought to be mediated by responses elicited by jasmonic acid (JA), a subset of which are lipoxygenase 3 (LOX3) dependent. To understand the importance of LOX3-mediated insect resistance, we analysed the performance of Manduca sexta larvae on wild-type (WT) and on isogenic Nicotiana attenuata plants silenced in NaLOX3 expression and JA signalling, and we used Waldbauer nutritional indices to measure the pre- and post-ingestive effects. LOX3-mediated defenses reduced larval growth, consumption and frass production. These defenses reduced how efficiently late-instar larvae converted digested food to body mass (ECD). In contrast, LOX3-mediated defenses decreased approximate digestibility (AD) in early instar larvae without affecting the ECD and total food consumption. Larvae of all instars feeding on defended WT plants behaviourally compensate for their reduced body mass by consuming more food per unit of body mass gain. We suggest that larvae feeding on plants silenced in NaLOX3 expression (as-lox) initially increase their AD, which in turn enables them to consume more food in the later stages and consequently, to increase their ECD and efficiency of conversion of ingested food (ECI). We conclude that N. attenuata's oxylipin-mediated defenses are important for resisting attack from M. sexta larvae, and that Waldbauer nutritional assays reveal behavioural and physiological counter responses of insects to these plant defenses.

Influence of larval frass extracts on the oviposition behaviour of Monochamus alternatus (Col., Cerambycidae)

Abstract: The oviposition behaviour and response of adult females of Monochamus alternatus to short lengths (bolts) of Pinus massoniana trunks treated with hexane extracts of larval frass of M. alternatus was investigated in the laboratory. Females gnawed significantly fewer oviposition scars, and deposited significantly fewer eggs, on extract‐treated bolts than on control bolts. These results suggest the presence of a possible oviposition deterrent in larval frass of M. alternatus. Hexane extracts of larval frass were analysed by gas chromatography–mass spectrometry, and α‐pinene, β‐pinene, 3‐carene, limonene, longifolene and butylated hydroxytoluene were identified. Experiments with synthetic mixtures indicated that a mixture of monoterpenes and butylated hydroxytoluene exhibited oviposition‐deterring activity.

Parasitism and Development ofConura acuta(Hymenoptera: Chalcididae) on Sugarcane Stalkborers (Lepidoptera: Crambidae) in Mexico

A 10-yr study was conducted in the Los Mochis sugarcane area in western Mexico to determine rates of parasitism by Conura acuta (F.), an indigenous pupal parasitoid of the stalkborers Diatraea considerata Heinrich and D. grandiosella Dyar. Parasitism by C. acuta was practically zero in 1993, progressively increased soon after chemical insecticide applications were discontinued in the sugarcane area, peaked at a yearly average of 3.2% in 1997, and stabilized thereafter at 2–3%, except in 2000 and 2002, probably because of drought. Seasonal parasitism by C. acuta was density-dependent, with maximum parasitism occurring during summer, when hosts were more abundant. Maximum parasitism by C. acuta occurred during mid-September 1996 with 43.3%. Although parasitism by C. acuta was generally low throughout the study, its impact may be important in terms of indispensable mortality, late in the life history of stalkborers. No field parasitism by C. acuta was observed on Eoreuma loftini (Dyar), a concurrent sugarcane stalkborer in this area. In the laboratory, the most preferred hosts by C. acuta were D. grandiosella and D. considerata with 60% parasitism, whereas E. loftini, D. saccharalis (F.), and Spodoptera frugiperda (J. E. Smith) were poorly accepted (<5%). Parasitism was highest in the youngest pupae (1 d old) and decreased progressively with host age. Late-instar larvae and prepupae were not accepted, showing that C. acuta is a true pupal parasitoid (idiobiont). Attraction and parasitism by C. acuta were higher when pupae were exposed with larval frass compared with clean pupae, suggesting the presence of a kairomone in the process of host finding and acceptance. Developmental time of C. acuta was 10 d longer on D. considerata than on D. grandiosella, with no difference between parasitoid sexes within hosts. In contrast, C. acuta longevity did not differ after emerging from either host species, with females living >20 d longer than males. Opportunities for using C. acuta, the only known pupal parasitoid of sugarcane stalkborers in Mexico, as a biological control agent are discussed.

Responses of the stem borer larval endoparasitoid Cotesia flavipes (Hymenoptera: Braconidae) to plant derived synomones: Laboratory and field cage experiments

Laboratory and field cage experiments investigated the response of females of the stem borer larval endoparasitoid Cotesia flavipes to two synthetic synomone components, the terpenoid (E)-β-farnesene and the green leaf volatile, (Z)-3-hexenyl acetate, both compounds identified previously in headspace volatiles of maize plants damaged by stem borer (Chilo partellus). In dose response tests performed in a Y-tube olfactometer, parasitoids were significantly more attracted to the arms bearing 10 or 15 µg of (Z)-3-hexenyl acetate and (E)-β-farnesene than to the control arm. (E)-β-Farnesene was as attractive as the essential oil from the plant Hemizygia petiolata (Lamiaceae) rich in the same compound (80% relative amount). The plant essential oil elicited responses from females of the parasitoid comparable to those elicited by two positive controls, stem borer larval frass and adult parasitoid diet (20% honey solution), tested in the laboratory assays. In field cage trapping experiments, captures in traps baited with the terpenoid, the plant essential oil, (Z)-3-hexenyl acetate and the control of 20% honey solution, were not significantly different relative to captures in unbaited traps. Addition of the green leaf volatile (Z)-3-hexenyl acetate to the plant essential oil to yield a 1:1 two-component blend captured significantly more female parasitoids than traps baited with either of the two components alone. The results show that blends of green leaf volatiles and sesquiterpenoids may have potential in monitoring C. flavipes populations in the field.

Oviposition Deterrents in Larval Frass of Four Ostrinia Species Fed on an Artificial Diet

Behavioral bioassays have shown that volatile oviposition-deterring chemicals are present in the frass of Ostrinia zealis, O. furnacalis, O. scapulalis, and O. latipennis larvae fed on an artificial diet. These chemicals were extractable with acetone, and could be partitioned into a polar lipid fraction. This fraction mainly included palmitic, stearic, oleic, linoleic, and linolenic acids. No significant differences among the four Ostrinia species were found in the amount and composition of these free fatty acids. A mixture of the five authentic fatty acids of the composition found in the larval frass of O. zealis exhibited significant oviposition-deterring effects on all four species.

Hostplant suitability and defensive chemistry of the Catalpa sphinx, Ceratomia catalpae.

The growth and survival of the Catalpa sphinx, Ceratomia catalpae (Sphingidae), were measured on five different species of Catalpa: C. bignonioides, C. bungeii, C. fargeseii, C. ovata, and C. speciosa. Larval growth varied significantly among these host plant species; however, survival did not differ. Quantification of the iridoid glycoside content of larvae, pupae, adults, larval frass, and leaves of the larval host plant, C. bignonioides, by gas chromatography showed that leaves contained both catalpol and catalposide; larvae, pupae, and frass contained only catalpol; and the adults contained no detectable iridoid glycosides. Amounts were highest in the larvae and declined in the pupal stage. Very small amounts of catalpol were detected in adults of the parasitoid, Cotesia congregata, and in the silken cocoons. The hemolymph in which the parasitoid larvae grew contained over 50% dry weight catalpol. Larvae of C. catalpae often regurgitate when disturbed. This may serve as a defense against predators. A comparison of the growth of larvae pinched with forceps to induce regurgitation with those that were not so treated showed that larvae that were pinched, and usually regurgitated, grew significantly more slowly than those that were not.