274 LECTUKES ON BIOLOGY 



worshipped as the emblem of a world-creating Divinity. Even 

 to-day in many of the Southern countries a scarabseus cut in 

 precious stone and worn on the breast is regarded as an unfailing 

 remedy against the sterility of women. These beetles are, like 

 their near relative the horse-dung beetle, very partial to this 

 useful but not very appetizing material. By joint labour male 

 and female shape the dung into large balls which they drag 

 and roll to some hole. Here the ball is pulled to pieces and 

 carefully cleared of all parasites ; the female then lays her eggs 

 and the ball is reformed. 



In many species of the Libellulidse both sexes participate in 

 egg-laying and the care for the further development of the eggs. 

 According to Tiimpel, in Libellula cancellata the male seizes 

 the fertilized female, drags her to the nearest water, and compels 

 her, by rapidly moving his abdomen up and down towards the 

 water, to make also with her abdomen whipping movements, as 

 the result of which the gelatine-covered eggs fall into the water. 

 In another species of Libellulida, Lestes sponsa, the care of the 

 parent goes still further. After fertilization both sexes united fly 

 to a rush; to this the female clings, pushing by means of her 

 ovipostor one egg after the other under the surface of the stem. 

 During this process they descend slowly downwards to the 

 bottom of the pond, a thin layer of air, which covers the body 

 of the thoughtful parents, protecting them against drowning. 



Many Ephemeridse proceed in a similar manner, in particular 

 Beatis gemellus, and other related species, but here the perilous 

 dive is undertaken by the female alone. As soon as the 

 period of egg-laying approaches she compresses her wings and 

 surrounded by an air-bubble as by a diving-bell, she descends 

 to the bottom of the pond where she carefully conceals the eggs 

 under stones. As soon as the work is done she attempts to rise 

 once more to the surface, but only too frequently strength fails 

 and an early death is the reward of her sacrifice and courage. 



Numerous other insects, as for instance most butterflies, are 

 content to deposit their eggs in the neighbourhood of a suitable 

 food-supply. They are guided by an unerring instinct, so that 

 even when during the adult stage they have passed to a widely 

 divergent mode of life and acquired other needs they yet never 

 make a mistake. This astonishing instinct is one of the most 



