Males of the mining bee Andrena vaga

The solitary bee Andrena vaga is nesting in spring in large aggregations in sandy soil. The females collect willow pollen as food for their larvae. Males are emerging a few days before the females. So at the start of the nesting season the males are patrolling, at a height of a few cm, above nesting aggregations searching for emerging females. When a female is detected the male is starting chasing behaviour. In this state of development of the aggregation, with many males and only a few females, males are pouncing upon every dark piece of material even upon a piece of charcoal.

In the figure(animation) the soil is seen from above.  A fresh dead female is positioned at the lower left corner, a piece of charcoal is positioned at the upper right corner. The male is starting near the charcoal and is moving with a loop to the female. At the end a second male is entering the field of view from the right.

Andrena_240310_1316B_anim

 The behaviour has been filmed with 100 frames /s. The male position and direction of the body has been measured from the film. In the graph given below the male position and direction is given by a line with a dot. The dot is the position of the male face, the line is indicating the direction of the long axis of the body. The lines are drawn in 30 ms intervals. The female position is given by “o” for each 30 ms interval. In the graph given below the male is at first patrolling through the nesting site. At some moment the female is detected and the male is starting chasing behaviour.  In the graph, the unit of length is 1 cm.  The moment of detection of the female is deduced from circumstantial evidence, i.e. a change in the direction of the body or a change in velocity.

Figure_3_small

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