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Apidae

0.61 ± 0.13

100

61.3 ± 13.5

Orthoptera

0.10 ± 0.10

145

14.5 ± 14.5

Syrphidae

0.05 ± 0.02

10

0.5 ± 0.2

Araneae

0.03 ± 0.03

20

0.7 ± 0.7

Homoptera

0.03 ± 0.03

4

0.1 ± 0.1

Heteroptera

0.02 ± 0.02

15

0.3 ± 0.3

Coleoptera

0.02 ± 0.02

10

0.2 ± 0.2

Lepidoptera

0.02 ± 0.02

45

0.9 ± 0.9

Unidentified

0.21 ± 0.11

10

2.1 ± 1.2

Total

1.09 ± 0.29

80.6 ± 26.2

Tab. 3. Estimate of the average daily catch of larger-sized prey (fresh weight web

  • -

    1

day

bruennichi near Zurich (overall mean ± SE, of three consecutive days in early August).

  • -

    1

) of Argiope

Prey type

Weight per

Weight of prey

prey item

-1 caught web day

(in mg)

(in mg)

  • -

    1

Number of prey c a u g h t w e b - 1 d a y

  • -

    1

from 11:00 to 18:00 hours on three days in August, resulting in an overall m e a n c a p t u r e r a t e o f 4 . 8 7 ± 4 . 6 3 p r e y w e b - 1 d a y - 1 w h i c h i s v e r y s i m i l a r own estimate. My estimate and that of Ludy (2007) fall within the range of published estimates for A. bruennichi and other Argiope species (Tab. 4). t o m y

The daily catch of prey (in terms of numbers) has been converted to prey b i o m a s s c a u g h t w e b - 1 d a y - 1 ( T a b . 3 ) . T h i s y i e l d e d a n e s t i m a t e d a v e r a g e c a t c h o f p r e y o f a p p r o x . 8 0 m g f r e s h w e i g h t w e b - 1 d a y - 1 , c o n s i d e r i n g t h e l a r g prey (Tab. 3). Though tiny insects were not recorded in Tab. 3, it is known from other investigations that tiny insects compose, on average, roughly 10% of the total prey biomass of A. bruennichi (Nyffeler 1982; Malt 1996a) and of other Argiope spiders (Nentwig 1985; Bradley 1993). Taking this into consid- eration, the weight of prey of all sizes captured by A. bruennichi in my study e r - s i z e d

in early August can be estimated at approx. 90 mg web

  • -

    1

d a y - 1 , w h i c h i s t h e

equivalent of the weight of a worker honey bee. This estimate relates to adult females only, occurring in August and September, that spin strong, large webs. Of course the prey capture rate is a seasonally changing variable; the imma- ture stages of A. bruennichi, occurring between May and mid-July, make small- er webs and capture less food (Malt 1996a; Nyffeler unpubl.).

Prey catch of Argiope bruennichi

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