Euseius fustis (Pritchard & Baker)

K, Moustapha Touré, KwadjoK, Koffi Eric, DoumbiaK, Mamadou & KreiterK, Serge, 2025, New records of species of the family Phytoseiidae (Acari: Mesostigmata) from Ivory Coast, Acarologia 65 (1), pp. 3-35 : 23

Euseius fustis (Pritchard & Baker)

Amblyseius (Amblyseius) fustis Pritchard & Baker, 1962: 283 ; Ueckermann & Loots, 1988: 83. Euseius fustis, Matthysse & Denmark, 1981: 348 ; Moraes et al. 1986: 45, 2004b: 69 ; Moraes

& McMurtry, 1988: 15; Chant & McMurtry 2005b: 215, 2007: 121.

Bruce-Oliver et al. (1996) have tested various foods associated with cassava for their effect on the development, fecundity and longevity of Euseius fustis , the most common phytoseiid species found on cassava in Africa. Euseius fustis developed successfully to adulthood on the spider mite prey species Mononychellus tanajoa (Bondar) and Oligonychus gossypii (Zacher)

and on pollen from maize, castor bean, and cassava. Euseius fustis also completed development on water-diluted phloem exudate from cassava, diluted honeydew from the cassava mealybug and on various pollen and prey combinations. When reared on Tetranychus urticae Koch prey or free water only, E. fustis did not develop after the deutonymphal stage. All larvae held on clean leaf discs on water-soaked cotton died without moulting. Diets of maize plus castor bean pollen and maize pollen plus M. tanajoa resulted in the highest rate of development, the highest fecundity and the greatest longevity. Castor bean pollen alone and maize pollen alone produced a higher fecundity and greater longevity than M. tanajoa tested alone. A colony of

E. fustis reared continuously for seven generations on castor bean pollen produced nine times more adult females than a colony of E. fustis reared continuously on M. tanajoa . No negative effects on the development and fecundity of E. fustis were observed after seven generations were reared on pollen. On cassava, the leaf-dwelling Typhlodromalus manihoti and E. fustis occur on the middle leaves, whereas the apex-inhabiting T. aripo migrates from the apex to the top leaves only during the night ( Magalhaes et al. 2002). We found that differential distributions of these predators allow prey to escape predation by vertical migration to other plant strata. We studied the role of odours in the underlying prey behaviour on predator-free plants placed downwind from plants with predators and prey or with prey only. Prey showed increased vertical migration in response to predator-related odours. Moreover, these responses were specific: when exposed to odours associated with T. manihoti , prey migrated upwards,

irrespective of the plant stratum where they were placed. Odours associated with T. aripo triggered a flexible response: prey on the top leaves migrated downwards, whereas prey on the middle leaves migrated upwards. Odours associated with E. fustis , a low-risk predator, did not elicit vertical migration. Further experiments revealed that: (1) prey migrate up or down depending on the stratum where they are located, and (2) prey discrimination among predators is based upon the perception of predator species-specific body odours. Thus, at the scale of a single plant, odour-based enemy specification allows herbivorous mites to escape predation by vertical migration. This is the first record of this species from the Ivory Coast.

Specimens examined — a single specimen (1 ♀) collected between 05/IV/2017 and

17/IV/2018 14/III/2017 and 10/III/ 2018 in Abidjan, Anyama Ahoue (aasl 42 m, Lat 5°26′00.87″N,

Long 3°55′00.60″W) and 107 ♀♀ and 39 ♂♂ collected between 06/IV/2017 au 18/III/ 2018 in

Yamoussoukro, Ngattakro (aasl 158 m, Lat 6°49′39.443″N ; Long 5°17′21.635″W) on Carica papaya L.

World distribution — Benin, Burundi, Cape Verde, Congo, DR Congo, Ghana, Malawi,

Nigeria, Rwanda, Tanzania, Uganda, Zimbabwe.

Remarks — The measurements of specimens from the Ivory Coast (tables 13 and 14) are very close to those of specimens from other regions of Africa.