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First published online August 4, 2005
Journal of Experimental Biology 208, 3199-3209 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01759

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Influence of host size on the clutch size and developmental success of the gregarious ectoparasitoid Eulophus pennicornis (Nees) (Hymenoptera: Braconidae) attacking larvae of the tomato moth Lacanobia oleracea (L.) (Lepidoptera: Noctuidae)

H. A. Bell^*, G. C. Marris, A. J. Prickett and J. P. Edwards

Central Science Laboratory, Sand Hutton, York, YO41 1LZ, UK

View larger version (14K): [in a new window]   Fig. 1. The relationship between clutch size and host size for the first oviposition in naïve E. pennicornis females exposed to a single host larva in either the fifth or sixth stadium. Non-linear regression analysis: y=66.29–(70.62x0.0701x), r2=0.74, d.f.=102.

View larger version (23K): [in a new window]   Fig. 2. (A) The numbers of eggs oviposited onto hosts of differing sizes, and numbers of adult wasps that subsequently emerged. Columns for each data series headed by different letters are significantly different (one-way ANOVA, P<0.05). Values are means ± S.E.M.; numbers in parentheses indicate the N value. (B) The mean percentage survival of clutches developing from egg to adult for parasitized hosts of each mass category.

View larger version (35K): [in a new window]   Fig. 3. (A) The number of hosts parasitized when E. pennicornis females were provided with populations of L4, L5, L6 (and mixed L4–6 hosts) and (B) the number of eggs laid. Values are means ± S.E.M. For N values, see text. Bars headed by different letters are significantly different (one-way ANOVA of log-transformed data, P<0.05). (C,D) The relationship between longevity and the number of hosts parasitized for E. pennicornis females exposed to (C) L6 populations (linear regression analysis: y=0.5752x–0.5772, r2=0.62, F1,1321.56, P<0.001) and (D) mixed L4–L6 populations (linear regression analysis: y=0.5506x–0.044, r2=0.77, F1,13=43.5, P<0.001).

View larger version (18K): [in a new window]   Fig. 4. The relationship between clutch size and host size for E. pennicornis females exposed to host populations over their entire lifespans. (A,B) The first three ovipositions of females exposed to (A) mixed stadium hosts [non-linear regression analysis: y=9.58+(11.75x0.027x), r2=0.43, d.f.=39] and (B) all other ovipositions. (C,D) The clutch size–host size relationship for the first three ovipositions in parasitoids exposed to (C) L6 hosts only and (D) all subsequent ovipositions.

View larger version (28K): [in a new window]   Fig. 5. The proportion of all hosts parasitized by E. pennicornis, when provided with either mixed stadium hosts or L6 hosts only, in each host mass category. Values are means ±95% CL. N=110 (mixed hosts) and N=115 (L6 hosts).

View larger version (36K): [in a new window]   Fig. 6. (A,B) Mean clutch sizes in relation to (A) oviposition number and (B) the eggs:host wet mass (mg) of wasps exposed to mixed stadium and L6 only host populations. Values are means ± S.E.M., N=110 (mixed stadium hosts) and N=115 (L6 hosts). (C,D) Clutch sizes relative to time (from exposure to hosts) are shown for wasps exposed to the two host population types (C, mixed and D, L6). All wasps were 2 days old at the start of the experiments.

View larger version (17K): [in a new window]   Fig. 7. The growth of hosts following parasitism by E. pennicornis in either the fifth or sixth stadium. Growth of L6 hosts parasitized immediately after moulting (day 1) and 1 day later (day 2) (A) and growth of L5 hosts immediately after moulting (B). The growth of hosts parasitized on day 2 was similar to the growth curve plotted and the data is omitted for clarity. Values plotted are the mean mass (± S.E.M.) of 10–15 insects.