PROTECTION AGAINST UNBIDDEN GUESTS IoI 
way the nectar of numerous flowers, though it is easily got at by related species 
possessing a longer proboscis. They are Bombus terrester Z., and Bombus mastru- 
catus Gers?., 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 allurements. 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-guards. 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 mollis 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. Pl.” Eng. Ed. 1, 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, 
