Inventaire des oiseaux de la Reserve Naturelle Integrale de Zahamena,Madagascar

Hawkins, A.F.A., Andrianarimisa, A., Rakotonomenjanahary, O.M. & Raminoarisoa, V.M. 2000. Inventaire des oiseaux de la Reserve Naturelle Integrale de Zahamena, Madagascar. Ostrich 71 (1 & 2): 317.

Zahmena est une Reserve Naturelle Integrale de 73 160 ha situé dans le centre-est de Madagascar. Nous y avons visités 4 sites entre 465–1490 m d'altitude. Nous avons trouvé 17 espéces d'oiseaux inconnus jusque là dans là Reserve. Maintenant, un total de 108 espéces d'oiseaux est ainsi recensée dans la Reserve, y compris 36 de 38 espèces limitées aux forêts humides de l 'est de Madagascar. Le site le plus riche, tout au niveau des espèces forêtières qu'au niveau d'espèes menackes, était le site le plus oriental et le plus bas (Namarafana). Les communautkes d'oiseaux étaient diffbrents selon on se situait dans les montagnes ou en basse altitude. Parmi les espbces recensks se trouvaient l'Aigle Sexpentaire de Madagascar Eutriorchis astur et le Newtonie de Fanovana Newtonia fdnovanae, tous deux trouves uniquement dans le site situk a la plus basse altitude.     

Influence de l'elimination des parasites en surnombre sur la survie de la descendance des femelles vierges de Diadromus pulchellus, Hymenoptere, Ichneumonide

Résumé L'activité maximale de ponte des femelles vierges de Diadromus pulchellus Wsm., pourvues en hôtes 24 h après leur émergence, est atteinte au 9ème jour. Comme les femelles inséminées, les femelles vierges ont tendance à concentrer les pontes sur un même hôte car dans nos conditions expérimentales, un tiers des hôtes parasités ont été superparasités. Ce superparasitisme entraîne une perte de 31,1% des ufs émis. Les maximum d'hôtes parasités et superparasités sont atteints au moment de la plus forte activité de ponte.L'équivalence des effectifs des descendances théoriques (calculées à partir du nombre d'ufs sains émis) et des descendances réelles de femelles vierges, signifie d'une part, que, comme chez tous les hyménoptères à parthénogénèse arrhénotoque, les larves mâles issues d'ufs infertilisés sont hautement viables et d'autre part, que la larve victorieuse du combat larvaire atteint dans la majorité des cas le stade adulte libre.

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Summary This study of the egg-laying behaviour of virgin females of D. pulchellus shows the relations between fecundity, superparasitism and the number of progeny.The highest egg-laying activity of the D. pulchellus virgin females, allowed access to their hosts (Acrolepiopsis assectella) 24 hr after emergence, was observed on the 9th day. In our experimental conditions, where each female was allowed access to five hosts, renewed daily, for 25 days, three quarters of the hosts available were actually parasitised. As with the fertilized females, the virgins tend to concentrate their eggs on the same host, so that a third of the parasitised hosts were superparasitised, causing a loss of 31,1% of the eggs laid.The greatest numbers of parasitised and superparasitised hosts were reached during the period of maximum oviposition.The equivalence of the theoretical number of progeny (based on the number of healthy eggs laid) and the actual progeny, shows that the survivors of larvae, competing in the same host, generally reach the free imaginal state.

     

Facteurs de limitation des populationsd'Aphis fabae Scop. dans l'Ouest de la France

Résumé Le déclenchement dépizooties au sein de populations d'Aphis fabae sur féverole de printemps est largement d? aux facteurs climatiques et dépendant de l'h?te. Trois années d'expérimentations ont permis de préciser ces facteurs en conditions naturelles. Cette note insiste surtout sur les facteurs dépendant de l'h?te qui interviennent lorsque se prépare une épizootie: en particulier l'accent est mis sur la quantité minimum de pucerons mycosés requise et sur leur répartition au sein des colonies et de la culture.

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Summary A three-year study of the mechanisms involved in initiating epizootics onAphis fabae on field beans is reported. In 1969 and 1970, two field experiments were done at two sowing dates (with a month interval in 1969 and a fortnight in 1970); in 1971, only one could be conducted. Despite the two widely separated sowing dates, epizootics occurred at only a ten-day interval in 1969, and at the same time in 1970 in the two sowings. In 1971, there was a slow but steady progression of fungus attack, resulting in good control (fig. 1). Climatic factors, such as relative humidity above 90% for more than 10 hours per day, temperatures above 20°C and rains, are thought to be largely responsible for outbreaks; nevertheless, it is essential to have sufficient inoculum well-distributed among the population. It now seems that this quantity is better expressed as a minimum of 300 dead aphids per stem than as a percentage (table 1). As for inoculum distribution, dead aphids occur in any size of colony but, at the beginning they seem proportionately more numerous in the smaller colonies (fig. 2, 3). When epizootics are about to occur, the proportion of dead aphids is the same in all sizes of colony. Clearly, a well-spread production of inoculum will result from this apparent proportionality and from the distribution of aphid colonies in the field (fig. 3, 4, 5). Emphasis is laid on the difficulties of determining in field experiments whether the above factors are causal agents. Also, the threshold figure of 300 dead aphids per stem associated with the initiation of outbreaks may well vary under different ecological conditions.

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Stagiaire Hollandais du 12 mai au 23 ao?t 1969.     

Alcaloïdes des ecorces de racines de Crioceras dipladeniiflorus

Eight alkaloids have been isolated from the root bark of Crioceras dipladeniiflorus. Five of them are new: Δ¹⁴-vincamine (I) epi-16 Δ¹⁴-vincamine (II) 12-methoxy-δ ¹⁴-vincamine (V) apo Δ¹⁴- vincamine (VI), and ditabersonine (VII), a dimeric alkaloid; the three others are known, voaphylline (III), tabersonine, (IV), and vobtusine (VIII).     

Controle de validite des caryogrammes application au caryotype de lolium perenne L.

The precise morphological study of the chromosomes of Lolium perenne L. puts forwards the lack of a statistical method allowing to appreciate the distinction between the elements of a chromosomal stock for the establishment of a caryogram. The present method is based upon the comparisons of variances, using, as a check value, a comprehensive estimation of the purely random variation. This estimation must be done by avoiding two sources of error, which were not taken in consideration until now and result from the fluctuation process only: 1. Arbitrary separation in each cell of a set of 4 chromosomes which are not really distinguishable in two pairs, one to which a relatively high value is attributed, and the second to which a lower value is given. Both distributions obtained present very low variances which, when employed in order to test the significance of the difference between both means, wrongly confirm the value of the initial distinction. 2. Confusion of both arms in symmetrical chromosomes when establishing the C/L ratio. This has two consequences: decreasing the value of the variance and under estimation of the symmetry, and this so much the more than the actual symmetry is more complete. — Application of this method leads to consider as identical the f and g chromosomes of Lolium perenne and to separate by means of the total lengths (or the ratio T/Θ) the c and d pairs the morphological identity of which is, in other respects, remarkable. In addition, it is also interesting to note the clear manifestation of a satisfying homogeneity in the variation of the chromosomes and of their constituent arms.     

Description de Falklandia gen.n. de I'Ocean Austral et définition des Lysianassoidea uristidiens (Crustacea, Amphipoda)

The revision of the antarctic–subantarctic species Orchomenopsis reducta Schellenberg, 1931, has led to its attribution to a new, highly apomorphic genus: Falklandia gen.n. A new definition of the uristid group is given and Falklandia with 36 other lysianassoid genera are attributed to this supposedly monophyletic group.