Studies of the conditioned reflex in lower vertebrates

A defensive conditioned reflex was established in groups of fry of hatchery-reared and wild-born chum salmon, Onchorhynchus keta (Walbaum), using a plastic model of predatory fish as conditioned stimulus and an electric shock as unconditioned stimulus. Efficiency of elaboration, stability, and retention of the conditioned reflex were improved with age. In a group in which the majority of fish had been well conditioned, the poorly-reinforced minority followed the prevailing defensive movement of the majority group. The reflex to the fish model was readily generalized i.e., extended to other objects. Wild fry showed naturally-acquired, defensive behavior against the fish-model in the laboratory. Some artificially reinforced groups were marked on their fins and released upstream in a closed, experimental river-area, being recaptured downstream. The relatively high rate of survival in these groups proved the effectiveness of the elaborated defensive reflex against natural predators.     

Chemical composition and pheromonal function of the defensive secretions in the subtribe Stizopina (Coleptera, Tenebrionidae, Opatrini)

The chemical composition of the defensive secretions of 52 species from 15 genera of the tenebrionid subtribe Stizopina was analyzed. The secretions of all species contained 1,4-benzoquinones, 1-alkenes, and monoterpene hydrocarbons, only one species was lacking the latter. Methyl- and ethyl-1,4-benzoquinone were ubiquitous, mostly accompanied by smaller amounts of 1,4-benzoquinone as well as isopropyl- and propyl-1,4-benzoquinone. 1-Alkenes were dominated by 1-undecene with varying admixtures of other 1-alkenes. The monoterpene hydrocarbons always consisted of a mixture of α-pinene, camphene, β-pinene and limonene, but also p-cymene, α-terpinene or α-phellandrene were found in some species. Furthermore, some species synthesized additional compounds such as phenols, ketones, 2,5-dihydroxy-6-methylbenzoate, 2-hydroxy-4-methoxyacetophenone and naphthoquinones. Bioassays showed that the defensive secretion co-functioned as an aggregation pheromone in the subtribe Stizopina. All nine tested species from six genera were attracted to defensive secretion of Stizopina species, but they did not distinguish between defensive secretions of different Stizopina species. This lack of discrimination might be the initial step for the formation of interspecific aggregations and the evolution of cleptoparasitism within the Stizopina.     

Electrophysiological and behavioural responses of Aphidius ervi (Hymenoptera: Braconidae) to tomato plant volatiles

Flight responses of the aphid parasitoid Aphidius ervi to tomato volatiles have recently demonstrated that different plant stresses can lead to increases in attractiveness for this parasitoid. For example, infestation of tomato plants by the aphid Macrosiphum euphorbiae results in the overexpression of defensive genes, as well as the release of volatile compounds that attract aphid parasitoids. Here, we determine which of the induced compounds elicit a significant electrophysiological response from parasitoid antennae. Compounds shown to be detected at the antennal level were then tested at a range of doses in a wind tunnel assay. A significant electroantennogram response was demonstrated for three compounds, (8S,9R)-(E)-caryophyllene, methyl salicylate, and (Z)-3-hexen-1-ol, over four concentrations. These compounds proved to be significantly attractive in the wind tunnel at a rate not always proportionally dependent upon the dose. The practical implications of these findings are discussed in the framework of sustainable control for pest aphids in agriculture.     

Aggregation pheromone compounds of the black larder beetle Dermestes haemorrhoidalis Kuster (Coleoptera: Dermestidae)

Gas chromatography with simultaneous flame ionisation and electroantennographic detection (GC–EAD) and gas chromatography with mass spectrometry analysis (GC–MS) of abdominal extracts of adult male Dermestes haemorrhoidalis Kuster (Coleoptera: Dermestidae) revealed the presence of electrophysiologically and behaviourally active compounds to its conspecific males and females. Isopropyl dodecanoate (3), isopropyl (Z)-9-tetradecenoate (5), isopropyl tetradecanoate (6), isopropyl (Z)-9-hexadecenoate (7) and isopropyl hexadecanoate (8) were detected in male abdominal extracts only. Analysis of collected male headspace volatiles revealed the presence of six EAD-active compounds (3), (5), (6) and isopropyl tridecanoate (4) plus two unidentified compounds (1) and (9). Synthetic compounds (3), (4), (5), (6) and (7) showed EAD activity with antennae of both sexes in contrast to synthetic (8) which showed EAD activity with female antennae only. Male and female antennae of D. haemorrhoidalis reacted with high receptor potentials to isopropyl (Z)-9-dodecenoate (2), although this compound itself was detected in neither male nor female abdominal extracts or headspace volatiles. Petri dish bioassays indicated that male abdominal extracts and compounds (2), (3), (5) and (6) aroused and attracted conspecific male and female beetles significantly (P < 0.05) compared to female extracts. These results suggested the presence of a male-produced aggregation pheromone in D. haemorrhoidalis. Field assays with any of the described compounds, however, did not result in attraction of this beetle in significant numbers.     

Intraguild predation by <Emphasis Type="Italic">Harmonia axyridis</Emphasis> on coccinellids revealed by exogenous alkaloid sequestration

Summary.  Under laboratory conditions, the multicolored Asian lady beetle, Harmonia axyridis is well known as an intraguild predator of other ladybirds. However the real impact of this exotic species on native species was poorly investigated in the field. Because many ladybird species produce alkaloids as defensive compounds, we propose here a new method of intraguild predation monitoring in coccinellids based on alkaloid quantification by GC-MS. In laboratory experiments, adaline was unambiguously detected in fourth instar larvae of H. axyridis having ingested one egg or one first instar larva of Adalia bipunctata. Although prey alkaloids in the predator decreased with time, traces were still detected in pupae, exuviae and imagines of H. axyridis having ingested one prey when they were fourth instar larvae. Analysis of H. axyridis larvae collected in two potato fields shows for the first time in Europe the presence of exogenous alkaloids in 9 out of 28 individuals tested. This new method of intraguild predation detection could be used more widely to follow the interactions between predators and potential chemically defended insect preys.     

Hydroquinones from defensive secretion of a giant Pacific millipede, <Emphasis Type="Italic">Acladocricus setigerus</Emphasis> (Diplopoda: Spirobolida)

Summary. The presence of considerable quantities of hydroquinones including hydroquinone, 2-methylhydroquinone, 2,3- dimethoxyhydroquinone, 2-methoxy-3-methylhydroquinone, and 2,3-dimethoxy-5-methylhydroquinone renders the defensive secretion of Acladocricus setigerus (Silvestri, 1897) significantly different from that of other quinone-producing millipedes. In addition, two hitherto undescribed compounds, namely, 2,3-dimethoxy-5-methylhydroquinone and 2-methyl-3,4-methylenedioxyphenol, were characterized from the defensive secretion. However, it is uncertain if the latter compound is formed after the release of the secretion. The two major compounds, 2-methyl-1,4-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone, constitute about 75% of the defensive fluid. Furthermore, hydrocarbons, which are typically present in the secretions of most other arthropods that use benzoquinones as repellents, are notably absent in the secretion of A. setigerus.     

Age- and sex-related variation in defensive secretions of adult <Emphasis Type="Italic">Chlaenius cordicollis</Emphasis> and evidence for their role in sexual communication

Defensive secretions of adult Chlaenius cordicollis (Coleoptera: Carabidae) from Manitoba and Pennsylvania were analyzed across the life cycle in a multi-year study using solid phase microextraction and gas chromatography-mass spectrometry. In concurrent experiments using Y-tube olfactometry, we observed the response of each sex when male or female source beetles were induced to discharge defensive secretions. Almost all defensive secretion samples contained five alkylphenolic compounds, dominated by 3-methylphenol; frequently, two alkoxyphenolic compounds and one ester were also detected. As beetles aged, the composition of their defensive secretion shifted, showing an exponential decrease in the relative proportion of 2,3-dimethylphenol as a function of day of year. Previously reported differences observed in autumn between secretions of beetles from Manitoba and Pennsylvania are attributable to different times of onset of the decline of 2,3-dimethylphenol in the two locales. Regardless of airborne odor, responding beetles exhibited upwind anemotaxis in the olfactometer and, outside of the reproductive period, avoidance was the most frequent response to defensive secretions. Sexual dimorphism was evident in the major components of the defensive secretions during the reproductive period and resulted from an increase over time in 2,5-dimethylphenol in male beetles. In the reproductive period, neither sex avoided odor from male source beetles, females preferred clean air to odor from source females, and males were attracted to females that discharged defensive secretion but showed no preference when females had not discharged the secretion. The defensive secretion appears to function as a sex attractant during the reproductive period.     

Chemical studies on Indopacific Ceratosoma nudibranchs illuminate the protective role of their dorsal horn

Summary. Two Ceratosoma species, C. trilobatum and C. gracillimum (Mollusca: Gastropoda: Opistobranchia), collected along the South China Sea coast, have been studied in order to investigate their defensive strategies. Both species contain four typical sponge furanosesquiterpenoids, probably with a dietary origin. The tissue distribution of these compounds has been studied by ¹H-NMR analysis and preliminary bioassays have been carried out in order to evaluate the ecological role of the isolated metabolites. The main sesquiterpene component in both species was (–)-furodysinin (2), which showed significant feeding-deterrent and ichthyotoxic properties in bioassays with freshwater organisms. The work has been performed studying a very limited number of molluscs that prevented the realization of ecologically relevant experiments. However, the almost exclusive presence of compound 2 in the crude extract of the mantle glands concentrated in the dorsal horn of C. gracillimum strongly supports the defensive role of that dorsal protuberance, which probably acts as a defensive lure attracting potential predators to the part of the animal that contains the distasteful chemicals.     

Chemical defense of an earwig (Doru taeniatum)

Summary. The earwig Doru taeniatum (Dermaptera, Forficulidae) has a pair of defensive glands, opening on the 4th abdominal tergite, from which it discharges a spray when disturbed. It aims the discharges by revolving the abdomen, a maneuver that enables it simultaneously to use its pincers in defense. The secretion contains two quinones (methyl-1,4-benzoquinone and 2,3-dimethyl-1,4-benzoquinone) present in the glands as a crystalline mass, together with pentadecane and a (presumably) aqueous phase. The gland openings are minute, with the result that virtually no quinone crystals are expelled with the spray. Only the two liquid phases are discharged, together with the ca. 1% quinone they carry in solution. Such a solute-economizing discharge mechanism appears to be without parallel among insect defensive glands. Received 14 February 2000; accepted 21 February 2000     

Ladybird defence alkaloids: Structural,chemotaxonomic and biosynthetic aspects (Col.: Coccinellidae)

Summary The defensive mechanisms which protect ladybird beetles (Coccinellidae) against predators are reviewed. Besides behavioural mechanisms, such as thanatosis and reflex bleeding, chemical defence mechanisms are playing a prevalent role. Indeed, ladybirds are protected not only by their smell, but also by repulsive alkaloids, most of which are considered to be of autogenous origin. In a few cases, dietarily-acquired substances are also involved. Particular emphasis is laid on the repellent alkaloids which are contained in the haemolymph of many species. The structures of 34 nitrogen-containing compounds isolated so far are presented, and their distribution within the family is discussed in the light of the most widely accepted classification of these beetles. To conclude, the mode of release of the alkaloids, their variation through the life cycle and their repellent and toxic properties are discussed, as well as the few biosynthetic data yet available.     

Sequestration of plant pyrrolizidine alkaloids by chrysomelid beetles and selective transfer into the defensive secretions

Summary Oreina cacaliae andO. speciosissima (Coleoptera, Chrysomelidae) sequester in their elytral and pronotal defensive secretions pyrrolizidine alkaloids (PAs) as Noxides (PA N-oxides). The PA N-oxide patterns found in the beetles and their host plants were evaluated qualitatively and quantitatively by capillary gas chromatography/mass spectrometry (GC-MS). Of the three host plantsAdenostyles alliariae (Asteraceae) is the exclusive source for PA N-oxide sequestration in the defensive secretions of the beetles. With the exception of O-acetylseneciphylline the N-oxides of all PAs ofA. alliariae, i.e. senecionine, seneciphylline, spartioidine, integerrimine, platyphylline and neoplatyphylline were identified in the secretion. PA N-oxides typical ofSenecio fuchsii (Asteraceae) were detected in the bodies of the beetles but not in their secretion. No PAs were found in the leaves of the third host plant,Petasites paradoxus (Asteraceae). The results suggest the existence of two distinctive storage compartments for PA N-oxides in the beetle: (1) the defensive secretion, containing specifically PA N-oxides acquired fromA. alliariae; (2) the body of the beetle, sequestering additionally but less selectively PA N-oxides from other sources,e.g. S. fuchsii or monocrotaline N-oxide fed in the laboratory. The concentration of PA N-oxides in the defensive secretion is in the range of 0.1 to 0.3 mol/1, which is more than 2.5 orders of magnitude higher than that found in the body of the beetle. No significant differences exist in the ability of the two species of beetles to sequester PA N-oxides fromA. alliariae, althoughO. speciosissima, but notO. cacaliae, produces autogenous cardenolides. A negative correlation seems to exist between the concentrations of plant-derived PA N-oxides andde novo synthesized cardenolides in the defensive secretion ofO. speciosissima.     

Chemical defense and evolutionary trends in biosynthetic capacity among dorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia)

Summary. An evolutionary scenario incorporating recent advances in phylogenetic research begins with an opisthobranch-pulmonate common ancestor that was herbivorous and had some diet-derived chemical defense. The Nudibranchia and their closest relatives, the Notaspidea, form a lineage the ancestors of which had switched to feeding upon sponges and deriving protection from metabolites contained in them. Subsequently there have been repeated shifts in food and defensive metabolites, and trends are evident in the ability to detoxify, sequester and utilize metabolites from food, as well as to synthesize defensive compounds de novo. The Notaspidea display a minor adaptive radiation that foreshadows a more extensive one in the various lineages of nudibranchs. This review emphasizes changes that have occurred within the Holohepatica, or dorid nudibranchs (order Doridacea). Their sister-group, the Cladohepatica, consists of three other orders, Dendronotacea, Arminacea, and Aeolidiacea, in which there has been a shift from sponges to Cnidaria as food. The Dendronotacea often feed upon Octocorallia, which combine spicules, chemical defense, and stinging capsules and thereby suggest a transition from feeding on sponges. A previous diet of Octocorallia is suggested by the defensive use of prostaglandins in the dendronotacean Tethys fimbria, which eats crustaceans. A shift to bryozoans in some Arminacea is accompanied by use of different metabolites. Dorid nudibranchs evidently began as sponge-feeders, but some lineages have shifted to a variety of other food organisms, and others have specialized in the kind of sponges they feed on and how they do it. There have been shifts to bryozoans (Ectoprocta) and ascidians (Chordata: Urochordata) that track metabolites rather than the taxonomy of the food. There is a crude correlation between the genealogy and the defensive metabolites of the sponge-feeding dorids. De novo synthesis is well documented in this order and the metabolites are appropriately positioned so as to have an adaptive effect. The hypothesis that the capacity for de novo synthesis was acquired by gene transfer across lineages is rejected, partly on the basis of different chirality of metabolites in the nudibranchs and their food organisms. Instead it is proposed that there has been a preadaptive phase followed by evolution in a retrosynthetic mode, with selection favoring enzymes that enhance the yield of end products that are already present in the food. Received 5 February 1999; accepted 26 July 1999     

Quantitative composition of the defensive secretion ofBledius species (Coleoptera: Staphylinidae: Oxytelinae) is adapted to naturally occurring predators

Summary The adaptation of defensive secretions to their target organisms was examined for the abdominal gland secretions ofBledius furcatus, B. spectabilis andB. arenarius. Therefore the target organisms of the secretion of theseBledius species (i.e. their predators) had to be identified. At the collection sites examined these were the earwigLabidura riparia, the antCataglyphis bicolor, the flyLispe candicans, different carabids of the generaPogonus, Dichirotrichus, Dyschirius, Bembidion andCalathus and the wading birdsHaematopus ostralegus andCalidris alba. The secretion of the abdominal glands contains the toxin ptoluquinone dissolved in either-dodecalactone and 1-undecene (B. furcatus andB. spectabilis) or in octanoic acid and octyloctanoate (B. arenarius). The ratio of these solvents is species-specific. Application experiments using some of the natural insect predators (L. riparia, C. bicolor, Pogonus, Di. gustavii, Dyschirius) revealed that these solvent ratios provided a more effective deterrent than other possible ratios. Thus by combining the solvents in certain ratios, the capability of cuticular penetration and therefore the effectiveness of the defensive secretions are adapted to their natural targets.     

Inter-individual variation in sequestration (as measured by energy dispersive spectroscopy) predicts efficacy of defensive secretion in lubber grasshoppers

Summary. We tested whether inter-individual variation in concentration of sequestered compounds predicts defensive efficacy of the defensive secretion of onion-fed Eastern lubber grasshoppers. When fed onion, lubbers have the ability to sequester sulfur compounds into their defensive secretion, and the secretion from onion-fed lubbers is more deterrent of ants than the secretion from lubbers fed other diets (Jones et al. 1989). To test three hypotheses, we developed a method for measuring total sequestered sulfur in the secretion using energy dispersive spectroscopy (EDS). First, we found that lubbers fed an ad libitum, monophagous diet of onion produce more secretion and have higher concentrations of total sulfur in their secretions than lubbers fed other diets. These sulfur concentrations varied three-fold; we believe that this variation in the composition of defensive secretions stems from physiological variation. Second, our method was sensitive enough to detect sulfur in the secretion of some lubbers that had been fed onion only once. Third, the sulfur concentration of a secretion sample significantly predicted its ability to deter ants from foraging. Hence, our results suggest that inter-individual variation in defensive chemistry in insects offered the same diet may be ecologically important. Received 25 November 1997; accepted 5 February 1998.     

Blood sugar metabolism during moulting in the isopod crustacean Ligia exotica

Blood sugar metabolism of the isopod Ligia exotica Roux was studied in relation to chitin synthesis during the moult cycle. The blood sugars were found to occur free, as well as bound with blood proteins, during all moult stages, as in Emerita asiatica. The variety of free blood sugars is smaller in L. exotica; it comprises only glucose and glucose-6-phosphate. The protein-bound blood sugars are glucose and glucosamine. The blood-volume values do not differ markedly during the moult cycle. Estimations of blood sugars showed a marked rise of sugar levels in the blood during the premoult phase, and a subsequent fall during the freshmoult phase, when chitin is actively synthesised. The chitin values also showed a definite correlation with the blood-sugar values. The increased resorption of chitin during the premoult stage, and its liberation into the blood stream as glucosamine, is indicative of its reutilisation in chitin synthesis as in E. asiatica and the genus Cecropia. As more immediate precursors of chitin, such as uridine diphosphate and uridine diphophate acetylglucosamine compounds, were absent in the blood, a thorough biochemical study of the epidermis is suggested to locate the intermediate precursors of chitin which are possibly derived from blood sugars.     

Larval chemical defence and evolution of host shifts in Chrysomela leaf beetles

Summary. Larvae of Chrysomela leaf beetles release for defence volatile compounds belonging to various chemical families. This study focuses on the defensive strategy based on the esterification of isobutyric acid and 2-methylbutyric acid with a wide variety of alcohols taken up from the host plant. To date, only two species are known to produce these repellents C. interrupta, which is associated with Betulaceae and C. lapponica which occurs either on Betulaceae or Salicaceae.? In order to know if other species have developed this chemical defence and how the food plant influences the secretion of these toxins, we targeted by mass spectrometry the presence of iso- and 2-methylbutyric acids and esters of them in the defensive secretions of Chrysomela larvae exclusively associated with Betulaceae or Salicaceae. ?Screening analyses reveal that the synthesis of these compounds is a common character restricted to all the members belonging to the C. interrupta group sensu Brown (1956) regardless of the host-plant family. These results suggest that the biochemical mechanism leading to the synthesis of these compounds could be considered as a synapomorphy meaning that the group is probably monophyletic. ?Defensive secretions of the members of the interrupta group are quantitatively assayed for iso- and 2-methylbutyric acids and their (Z)-3-hexenyl esters. Results reveal a chemical plasticity developed by Chrysomela species associated with Salicaceae. The amounts of iso- and 2-methylbutyric acids derivatives and of salicylaldehyde in their larval secretions depend on the food plant and on its content in phenolglucosides. Received 5 October 1998; accepted 25 November 1998.     

Chemoecological studies of the exocrine glandular larval secretions of two chrysomelid species (Coleoptera):Phaedon cochleariae andChrysomela lapponica

Summary The exocrine glandular secretions of larvae of the subfamily Chrysomelinae are known to repel conspecific adults, other competitive phytophagous insects and natural enemies. InPhaedon cochleariae, the intraspecific activity of tlc fractions of the larval secretion was tested in order to examine the ecological significance of two fractions containing minor components and a fraction containing the major compound, the cyclopentanoid monoterpene (epi)chrysomelidial. InChrysomela lapponica, the defensive activity of the larval secretion against ants is known from specimens feeding upon willow or birch. The feeding preferences of larvae and adults ofC. lapponica from a Finnish and a Czech population were tested. The Finnish individuals significantly preferred feeding uponSalix borealis, whereas they hardly fed upon birch. The Czech specimens clearly preferred birch (Betula pubescens) to willow species. Application of salicin onto leaves of a willow species free of this phenolglycoside revealed that the Finnish individuals preferred feeding upon leaves with salicin. On the other hand, the Czech individuals avoided feeding upon leaves ofB. pubescens treated with salicin. The chemical composition of the glandular secretion of the Finnish larvae differed from the one of the Czech larvae. GC-MS-analyses of the secretions revealed that salicylaldehyde was the only major component of the secretion of Finnish larvae feeding upon the salicin-containing willowS. borealis. The glandular secretion of the Czech larvae feeding upon birch contained numerous esters of isobutyric acid and 2-methylbutyric acid. When Czech larvae had fed upon a salicin-containing willow (S. fragilis), the major compounds of their secretion were benzoic acid, salicylalcohol and benzoic acid esters; salicylaldehyde was only detected in traces. Thus,C. lapponica individuals from the Finland population adapted so closely to a salicincontaining willow that they clearly prefer this plant for food and that they obviously derive their main larval defensive compound (salicylaldehyde) from their host-plant.     

Nutrient availability and accumulation of phenolic compounds in the brown alga Fucus vesiculosus

Plant phenols tend to accumulate under conditions where plants have excess carbon above the level which can be used for growth, and where phenylalanine, the substrate of phenylpropanoid synthesis, accumulates due to suppressed protein synthesis. These internal balances imply an accumulation of phenols as a consequence of nitrogen deficiency suppressing plant primary metabolism. In three sublittoral populations of the brown alga Fucus vesiculosus (L.) collected from the northern Baltic Sea between May and September 1982, the accumulation of phenolic compounds correlated inversely with nitrogen content of thallus; higher phenolic contents were on average found under nitrogen deficiency. Phenolic content did not correlate with carbon content of thallus as such, while a significant negative correlation was found with the nitrogen: carbon ratio. Phenolic compounds, although having possibly defensive functions in plants, may thus partially vary as a function of resource availability rather than as a result of an active allocation into plant defences.     

Sesquiterpene Hydrocarbons: Kairomones with a releaser effect in the sexual communication of the white-spotted longicorn beetle, <Emphasis Type="Italic">Anoplophora malasiaca</Emphasis> (Thomson) (Coleoptera: Cerambycidae)

Summary.  We conducted a series of experiments with the white-spotted longicorn beetle Anoplophora malasiaca (Thomson), and its host plant, Citrus unshiu, to examine the origin of the sesquiterpene hydrocarbons (SHCs; including β-elemene, β-caryophyllene, α-humulene, α-farnesene, and several unidentified compounds) that are contained in the elytra of the beetles and act as an attractant. In the laboratory, mechanically wounded citrus branches, as well as those fed upon by A. malasiaca, attracted males more frequently than intact branches. Solid phase microextraction (SPME) and subsequent analyses by gas chromatography (GC) analyses detected measurable SHCs from the air around both mechanically wounded and beetle-infested branches, as well as trace amounts from intact branches. The SHCs were also detected for a certain time from beetles that had fed on the citrus branches, but the amounts decreased rapidly after they were removed from the host. This decrease generally corresponded with a reduction of attractiveness of the beetles in a behavioural assay. Isolated females acquired the SHCs after exposure to, but not upon contact with, other females that had fed on C. unshiu branches. We hypothesize that the citrus SHCs are adsorbed in, retained on, and released from the wax layer of the beetle elytra. Since these compounds are released from branches when beetles feed, they may indirectly signal the presence of beetles to others in the field. The high response rate to SHCs by males is likely representing mate searching behavior. The SHCs act as kairomones with a releaser effect in the communication system of A. malasiaca. Hiroe Yasui, Toshiharu Akino, Midori Fukaya: These authors contributed equally to this article.     

Protein and amino acid composition of the tergal gland secretions ofBlatta orientalis andEurycotis floridana (Dictyoptera: Blattidae)

Summary Nymphs and adult females ofBlatta orientalis and nymphs ofEurycotis floridana produce a proteinaceous sticky secretion which accumulates on the last abdominal tergites. The proteic patterns do not differ between individuals of the same species. HPLC analyses show that all the common amino acids are found in both species, aspartic and glutamic acids representing 24 to 37% of the total amount of amino acids. InB. orientalis, glutamic acid is the more abundant amino acid whereas inE. floridana it is the aspartic acid. The secretion appears and accumulates rapidly on isolated insects. Behavioural assays revealed that these secretions have a defensive role.