The population biology of the Orange Tip butterfly Anthocharis cardamines in Britain

ABSTRACT.

• 1 The population biology of Anthocharis cardamines (L.) is described and shown to vary with locality. Southern and Western populations emerge earlier than Northern ones, but Western and Northern populations occupy similar, wetter habitats and are associated primarily with Cardamine pratensis (L.). Southern populations are recorded mostly from Alliaria petiolata (Bieb.).
• 2 Studies on egg and larval survival indicate that host plant-induced death and parasitization by a tachinid are important mortality factors. However, a key-factor analysis on one population indicates that the major determinant of population size may be the number of eggs laid by ovipositing females, itself dependent upon weather during the oviposition period. Populations in different localities do show similar trends in abundance, corroborating the effect of weather.
• 3 Human effects on distribution and abundance are discussed, and some conservation strategies suggested.

     

An airflow olfactometer for measuring olfactory responses of hymenopterous parasitoids and other small insects

ABSTRACT. A new type of airflow olfactometer is described, and results given of experiments using it to measure behavioural olfactory responses of hymenopterous parasitoids. Compared with Y-tube olfactometers it shows several advantages. In its exposure chamber four separate abutting odour fields are presented so that the test insect can readily enter and re-enter them. More than one odour (or different concentrations of one odour) can be tested at the same time, thereby providing complex preference test situations. The various behavioural measures that can be assessed in the apparatus are examined and discussed.     

The role of Acanthospermum hispidum in the phenology of Euschistus heros and of Nezara viridula

Laboratory, greenhouse, and field studies with Euschistus heros (F.) and Nezara viridula (L.) (Heteroptera: Pentatomidae) in northern Paraná, Brazil, demonstrated greater survival and longevity with E. heros than N. viridula when fed the weed Acanthospermum hispidum DC. (Compositae). E. heros was better adapted to A. hispidum than N. viridula but neither species reproduced on this plant. Stink bugs moved from soybean to A. hispidum mainly during mid-March to mid-April when soybean plants matured. The infestation reached 60 and 100% with a maximum of ca. 3 and 10 stink bugs/plant in 1988 and 1989, respectively. Surprisingly, E. heros and N. viridula, which are normally seed-feeders, strongly preferred the high moisture stems of A. hispidum. Both species demonstrated similar feeding frequencies. These results suggest that in northern Paraná, the common weed, A. hispidum functions as a temporary host providing water and nutrients to those two pentatomid pests of soybean. Finally, both species do not seem to recognize A. hispidum as an unsuitable or perhaps toxic plant.     

The influence of phenolic compounds on the suitability of three Salix species as hosts for the willow beetle Phratora vulgatissima

The phenolic glycosides salicin and salicortin were found to influence larval growth and development rates and adult feeding preference of Phratora vulgatissima in laboratory feeding studies. Salicortin was more toxic to larvae than salicin, and none of the third instar larvae fed on Salix viminalis leaves amended with 1.52% (fresh mass) salicortin pupated. Condensed tannins (proanthocyanadins) did not affect larval performance. It was concluded that Salix burjatica resistance to willow beetle is due to the high levels of salicortin which occur in leaves of this species.     

Decision to superparasitize based on larval survival: competition between aphid parasitoids Aphidius ervi and Aphidius smithi

Oviposition by a parasitoid wasp in an already parasitized host (= superparasitism) may result in larval competition and the loss of offspring. Consequently, in solitary species, the decision to superparasitize should be based on the probability of offspring survival. Females of Aphidius ervi Haliday and A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae), two parasitoids of the pea aphid, discriminated between conspecific-and heterospecific-parasitized hosts. Both species showed partial preference for aphids previously attacked by A. smithi, a result predicted from the fact that A. ervi is superior to A. smithi in larval competition under most conditions. Females of A. smithi selectively attacked conspecific-parasitized pea aphids when given a choice between these and self-parasitized hosts. Results indicated that females of both species responded to an external pheromone-like marker to discriminate between selfconspecific-and heterospecific-parasitized aphids. In addition, A. smithi may use internal cues to recognize, and avoid oviposition in, aphids previously parasitized by A. ervi.

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Résumé L'oviposition par une guêpe parasite dans un hôte qui a déjà été parasité (= superparasitisme) pourrait conduire à une compétition entre larves et à une perte de progéniture. Par conséquent, dans les espèces solitaires, la décision de superparasiter devrait être basée sur la probabilité de survie de la progéniture. Les femelles de Aphidius ervi Haliday et de A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae), deux parasites du puceron du pois, ont discriminé entre les hôtes parasités par des individus de la même espèce et ceux parasités par des individus d'une espèce différente. Les deux espèces de parasite ont montré une préférence partielle pour les pucerons préalablement parasités par A. smithi, résultat qui était prévisible du fait que, dans la majorité des cas, A. ervi est supérieur à A. smithi dans la compétition entre larves. Les femelles de A. smithi ont sélectivement attaqué les pucerons parasités par un individu de la même espèce lorsqu'il leur était donné de choisir parmi ceux-ci et ceux parasités par les même individu. Les résultats indiquaient que les femelles des deux espèces répondaient à une sorte de phéromone externe pour distinguer les pucerons parasités par le même individu de ceux parasités par un individu de la même espèce et ceux parasités d'une autre espèce. En plus, A. smithi pourrait utiliser des signaux internes pour reconnaître et éviter l'oviposition dans les pucerons préalablement parasités par A. ervi.

     

Evaluation of Host Suitability in Prunus for Criconemella xenoplax

Methods were developed for screening Prunus selections for host suitability to Criconemella xenoplax. The relative host suitability of selections was based upon a doubling accumulation value (β) that was defined as the number of degree-days (base 9 C) required for doubling of an increment of the initial nematode population. The β value characteristic for C. xenoplax (139 ± 8 degree-days) on suitable hosts was similar to the average β value determined for several peach rootstocks known to be suitable hosts. The β values were 144 ± 21 for Halford, 141 ± 16 for Lovell, and 138 ± 10 for Nemaguard. A higher value for β could indicate poorer host suitability or resistance of a selection to C. xenoplax. All of 369 Prunus accessions tested, including eight accessions that had survived well on a field site infested with C. xenoplax, were suitable hosts. Apparently, resistance to C. xenoplax was not a factor in survival of the accessions planted in the field. Seedlings from P. besseyi, P. pumila ''Mando'', and two interspecific hybrids, Redcoat and Sapalta IR 549-1, failed to support nematode population increase in 44-81% of tests conducted, but all selections supported population increase in some tests. These accessions may have resistance mechanisms that are active only under specific conditions.     

草鱼免疫应答的初步研究

研究了草鱼在不同水温条件下受抗原刺激后其中和抗体的变化。15℃培养条件下中和抗体上升缓慢,9周内滴度低于1:8;20℃时,3周后抗体可上升到1:256,最高达1:5270,而在25℃时,1周中和抗体即达到1:570,最高可达1:20000以上。并探索了从草鱼血清中提纯抗体的条件,研究其抗体的特性。草鱼血清中的抗体为大分子蛋白,容易解离为抗原性相同,分子量近似于人IgG的较小分子,含有较多的二硫键,具有类似IgM的某些特性。     

Crucial factors determining the spatio-temporal distribution patterns of threeAthalia sawflies feeding on common cruciferous plants

Three Athalia sawflies, A. japonica, A. rosae and A. infumata, feeding on cruciferous plants, coexist in Japan. However, it is not known what ecological strategies they use and what environmental factors are crucial to such strategies. I attempted to explain these questions by examining the relationship between the spatio-temporal distribution patterns of three Athalia sawflies and their habitats in three districts (Lowland, Intermediate and Mountain). The three sawflies have different spatio-temporal distribution patterns, though they usually used common cruciferous plants. A. japonica was abundant in spring and autumn but disappeared during summer in all the districts. In the Lowland, populations of A. rosae and A. infumata, like that of A. japonica, crashed in summer. However A. rosae occurred mainly in summer in the Intermediate and Mountain. Although A. infumata occurred in the same seasons as A. rosae in all districts, population levels of A. infumata were always lower than those of A. rosae. The crucial factors controlling their population patterns were the availability of host plants and temperature. Population crashes of A. rosae and A. infumata were due to food depletion, and those of A. japonica were due to heat stress. On the other hand, their population patterns may be interpreted as phenological synchronization with their original host plants, though they all existed on common cruciferous plants. The three sawflies may have evolved different strategies to escape from unfavorable habitat conditions. Such strategies are speculated to be summer diapause in A. japonica, long distance migration in A. rosae, and local dispersal in A. infumata.     

Pasteuria sp. Parasitizing Trophonema okamotoi in Florida

Two populations of Trophonema okamotoi parasitized by Pasteuria sp. were found on Liquidambar styraciflua (sweetgum) and on an unidentified tropical grass in north-central Florida. Endospores of this Pasteuria sp. attached to motile vermiform second-stage juveniles (J2) and males of T. okamotoi, but not to other developmental stages. Sporangia and new endospores were produced only inside the bodies of swollen and sedentary third- and fourth-stage juveniles and females that developed in the host roots. No egg masses were produced by infected T. okamotoi females. The endospore diameter from the tropical grass population was 4.93 μm and the central core diameter was 1.97 μm; measurements of endospores from the sweetgum populations were similar. Endospores that were collected from T. okamotoi and added to uninfected T. okamotoi and other plant-parasitic nematodes attached/to J2 of T. okamotoi but did not attach to juveniles and adults of Helicotylenchus pseudorotrustus, Pratylenchus brachyurus, or to J2 of either Meloidogyne arenaria race 1, M. incognita race 1, M. javanica, or Tylenchulus semipenetrans. Pasteuria sp. from T. okamotoi differed from the described Pasteuria species in endospore size, host preference, and rate of attachment.