Behaviour of the parasitoid Lysiphlebia mirzai Shuja-Uddin (Hymenoptera, Aphidiidae) at varying host densities
1990
Tripathi, R.N. (Gorakhpur Univ. (India). Dept. of Zoology. Aphid-Biocontrol Lab.) | Singh, R.
The paper deals with the behaviour of Lysiphlebia mirzai, an aphidiid parasitoid of the pearl-millet aphid Rhopalosiphum maidis, at varying host densities. By increasing the host density on the leaf of the food plant Pennisetum typhoides, the parasitoid showed the following responses: 1. Host-searching time (leaf- and host-arrival time) significantly decreased curvilinearly. 2. The frequency of host contact with the ovipositor (stabbings or pricking) and oviposition into the hosts, first escape time total retention period with the host increased exponentially, and 3. the ratio of stabbing and oviposition decreased curvilinearly. The relationship between the number of eggs laid and the host density was described by a non-linear equation: Y = 54.0(10) exponent -718.2 fraction bar 468.5 + X exponent 2 where 54.0, - 718.2 and 468.5 are algebraic constant values and can be calculated from three points on the curve. This curve is sigmoidal, i.e., a steadily rising curve approaching a limit, Y = (54.0) which indicates that within given exposure period (30 min) in a space of about 530 cubic centimetres the number of eggs laid can not exceed 54.0. This type of response is similar to that of Holling's type 3 which is considered to be stabilising. L. mirzai tends to emigrate from an area where she has parasitised most of the hosts, particularly at low host densities. She tends to stay longer at higher host densities
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