PROTECTION AGAINST UNBIDDEN GUESTS loi 



way the nectar of numerous flowers, though it is easily got at by related species 

 possessing a longer proboscis. They are Bombus terrester L., and Bombus mastru- 

 catus Gerst., which, is very common in the Alps. These forms, by biting through the 

 nectar-containing organs from the outside, and introducing their proboscis into the 

 opening so made, steal the nectar, and are therefore not only useless to the plant, but 

 are frequently injurious. We may regard the inflated calyx of, e. g. Silene inflata, 

 as a protection against such nectar-thieves, for it is so far away from the inner floral 

 parts that they are not injured by the bites of these robbers. 



{d) By temporary cessation of allurevients. Flowers adapted to pollination by 

 nocturnal Lepidoptera are almost or entirely odourless by day, and frequently look 

 withered, while in the evening a stronger odour diffuses from them, and their petals 

 and stamens are fully expanded: Melandryum album, Silene nutans, Lonicera 

 Periclymenum and Caprifolium, Hesperis tristis, Pelargonium atratum and triste. 



{e) By ant-giiards. The nectaries already mentioned on p. 98, and which entice 

 ants, also occur on the involucral bracts of the heads of some Compositae. The ants 

 frequenting these heads in quest of nectar form a body-guard against beetles that eat 

 the flower-buds, especially cockchafers and rosechafers (Cetoniae). Observations 

 of the kind have been made on the capitula of several composites indigenous to 

 South Europe, especially on Centaurea alpina and ruthenica, Jurinea moUis and 

 Serratula lycopifolia. ' If one of the voracious beetles in question approaches, the 

 ants immediately assume a defensive attitude, holding on firmly to the involucral 

 bracts with the last pair of legs, and stretching the abdomen, the fore-legs, and 

 especially their powerful jaws, towards the enemy. They remain in this posture, 

 squirting out formic acid if necessary, till the marauder retreats ; and not till this 

 takes place do they once more peacefully turn their attention to the nectar ' (Kerner, 

 *Nat. Hist. PI.,' Eng. Ed. i, p. 243). On the capitulum of Jurinea mollis there are 

 often ten to fifteen ants of the species Camponotus Aethiops, and as many individuals 

 of Formica exsecta have been observed on that of Serratula lycopifolia. When the 

 capitula open, the beetles no longer settle upon the flowers, and the secretion of 

 nectar ceases, so that the ants also abandon their visits. 



Some flowers occasionally offer Shelter to their visitors, as well as pollen 

 or nectar. During sudden rain, nectar-seeking or pollen-collecting guests eagerly 

 take refuge under the overhanging upper lip of Labiates, in the flower-bells of species 

 of Campanula, and within other flowers. Some of these even afford shelter for the 

 night if the insects are overtaken by darkness while still at their work. 



I have, for instance (' Bl. u. Ins. a. d. nordfr. Ins.,' p. 165), observed honey-bees 

 making use of the upper lip of Lamium album as a shelter in rainy weather, and also 

 now and again humble-bees in the flowers of Campanula Trachelium and other 

 species, quite early in the morning, when the dew still lay on the plant, so that I was 

 compelled to suppose that they had spent the night there. For the most part, 

 however, it is smaller insects that seek shelter for the night in flowers or in- 

 florescences, e. g. small bees belonging to the genera Andrena, Halictus, and 

 Panurgus. The species of the first two of these stay overnight in the flowers of 

 Campanula more particularly, while the species of Panurgus often spend the hours 

 of darkness in the capitula of yellow-flowered composites (Crepis, Hieracium, 



