The life cycle and development of Zonocerus variegatus (variegated grasshopper) from southern Benin was studied at the International Institute of Tropical Agriculture (IITA) Benin Station, from March 1992 to August 1994. Hoppers of the 1st to the 5th stage were collected from uncultivated fields in the Atlantic Province and placed in cages and their development evaluated by counting the number of insects in each stage every two days until the adult stage. Mating and the number of egg pods were also recorded. The study showed that Z. variegatus has only one generation in southern Benin, running from September/October to July/August. Hatching occurs between September/ October and February/March. Zonocerus variegatus females can oviposit up to five times and the interval between ovipositions varies from 14 to 32 days. The variegated grasshopper has an egg diapause and egg hatching is not synchronised. These observations explain the almost perennial presence of the variegated grasshopper in southern Benin.

The life cycle of Baetis liebenauae has been investigated in a lowland spring of Northern Italy that shows a relative stability of water temperature. Nine postlarvula morphological stages of the larva were identified and a «jump development» of the wingpads between stage pairs has been noted. B. liebenauae is here a typical polyvoltine species and three generations can be defined, with the late-summer/autumn generation being the main one. During this generation the species is often the dominant taxon of the benthic community and shows a high larval density. Marquet differences have been in comparison noted with the development of this species in Poland. This is probably due to the different thermal features of the two regions. A temporal shift of the main generations seems to allow the coexistence of B. liebenauae and other high density Baetidae species. In Southern Europe the species is typical of small lowland streams with slow flowing waters. Its larvae live on aquatic macrophytes and their presence on mineral substrata can be considered as occasional.

Two successive generations of Epeorus sylvicola were studied in the Tifferguine, a torrential river in Morocco (2600 m altitude,water temperature 0-22° C, snow-cover : 1-2 months/year). The life cycle took one year and larval growth depended on temperature. Larvae fed on periphyton and lived mainly on stony substrates. In spring, macrophytes overgrew the bottom river and markedly reduced the amount of non-vegetated area ; combined with maximum and potentially lethal temperatures E. sylvicola larvae disappeared in May. Consequently, annual production depended on the development stage reached by the cohort when such unfavourable conditions occurred.

The host plant range of two ricefield caseworms, Parapoynx fluctuosalis (Zeller) and P. diminutalis Snellen (Lepidoptera: Pyralidae), was determined from screening rice and 61 weeds in the Philippines. Both species developed best on the aquatic weed Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae). Parapoynx fluctuosalis also completed a full generation from egg to egg on Cyperus brevifolius (Rottb.) Hassk. (Cyperaceae), Commelina diffusa Burm. f. (Commelinaceae), Leptochloa chinensis (L.) Nees, and Paspalum conjugatum Berg (Poaceae). Parapoynx diminutalis completed a generation on Chara vulgaris L. (Characeae), Ottelia alismoides (L.) Vahl and Blyxa auberti Rich. (Hydrocharitaceae), and Cyperus rotundus L. (Cyperaceae).

A wide spectrum of fish hosts in the Gulf of Guinea was examined for infestation with trypanorhynchid cestodes. A total of 1341 specimens belonging to 45 species were examined. The following 9 trypanorhynchid species were identified: Callitetrarhynchus gracilis, Grillotia perelica, Nybelinia sp., Otobothrium cysticum, O. dipsacum, Otobothrium sp., Poecilancistrum caryophyllum, Ptero-bothrium sp. and one unidentified species. The pattern of occurrence of Callitetrarhynchus gracilis has been used to draw conclusions on a possible 4-host life cycle of the species, involving two obligatory teleost host fish species, small clupeids and large predatory fish. The most abundant parasite was O. cysticum which was found in 8 host fishes. In general most other species occurred in one host fish species only. The study confirms the predominance of otobothriid cestodes in the parasite fauna of tropical and subtropical teleost fish species. Since only Pseudotolithus senegalensis and Stromateus fiatola harboured flesh infestations, trypanorhynchids do not pose serious dangers to the marketability of most commercially important fish species in the area. The method of scanning electron microscopy was used to clarify the details of hooklet arrangement on the tentacular armature of some species for the first time.

Le cycle biologique de Baetis navasi dure un an dans un torrent de montagne du Maroc (altitude 2 600 m) - Température 0-22° C. couvert de neige 1 mois par an). Les adultes volent en juin-juillet. Les larves se nourrissent de périphyton et vivent préférentiellement dans la végétation (Ranunculus aquatilis). La croissance larvaire est exponentielle et les taux de croissance (en poids sec) sont de 1,74 % par jour de juillet à décembre, proches de zéro en hiver et de 1,46 % par jour au printemps avant le début des émergences. La mortalité, forte dans les 2 premiers mois du cycle (4,9 % par jour) est plus faible de septembre à mars (1,16 % par jour) et nulle au printemps. La production annuelle peut être estimée à 440 mg de poids sec par m2. Le rapport production/Biomasse moyenne = 4,9.

Le cycle biologique des deux espèces a été étudié dans la nature et au laboratoire.L. minos vit en Crète, dans des lagunes saumâtres et à une température de 15° C. Les différents stades du développement sont présents pendant toute l'année. Des élevages ont montré que l'espèce était bivoltine et pouvait se développer en eau douce et à différentes températures.L. germanus vit en Europe Centrale. En Autriche, les larves habitent dans des étangs gelés en hiver. Les adultes sont essentiellement automnaux. L'espèce, normalement univoltine, est bivoltine en laboratoire à 10° ou à 15° C. Dans la nature elle doit subir une longue quiescence hivernale à l'état d'embryon ou de jeune larve.A l'émergence, les femelles des deux espèces sont immatures, mais ensuite leur développement génital est direct. Par contre, les femelles des autres espèces de Trichoptères, immatures à l'émergence, subissent une diapause estivale.

The serpentine leaf-miner Liriomyza trifolii is a new proliferous and polyphagous agricultural pest in Mauritius, attacking crops, ornamentals and weeds. Urgent chemical control measures had to be developed in order to save total crop loss, in particular potato, tomato, haricot beans, crucifers and onions. This insect is resistant to most insecticides. In view of formulating an integrated management programme, this paper reports on some aspects of practical importance concerning the biology and ecology of the leaf-miner, the incidence of damage, and the possibility of its control by natural plant products such as extracts of neem (Azadirachta indica). Steam distillates of neem leaves seriously affect larvae and pupae upon treatment by contact at as low a dose as 0.3% of the extract. Field treatments of onion plantations with aqueous neem extracts (0.5%) gave good protection to the crop. The current control measures are briefly considered.

Rhyacophila tristis Pictet a été étudiée durant 3 années consécutives dans un ruisseau pyrénéen (altitude 1 930 m — température maximum 17° C en août — couvert de neige 4-6 mois par an).Les larves sont essentiellement carnivores et se nourrissent surtout de chironomidae. Le développement larvaire dure 2 ans. La croissance s'effectue surtout en période déneigée. Entre le 1er et le 2e hiver de vie larvaire, l'accroissement (en poids sec) fut en moyenne de 2,25 % j-1. Durant cette période, 1,6 % des larves disparaissaient en moyenne chaque jour. Les taux instantanés de croissance et de mortalité demeurent voisins d'une génération à la suivante. La production a été estimée à 240 mg m-2 an -1. Le rapport Production/Biomasse moyenne annuelle = 3,1.