HYMENOPTERA PETIOLATA. 



763 



B 



FIG. 494. a hind leg of a 

 worker of Apis mellifica ; 

 K basket on the tibia ; 

 B enlarged tarsal joint 

 with brush on the under 

 side ; b brush, more 

 strongly magnified. 



the cane-sugar of the nectar has become the grape-sugar of honey. The 

 solitary bees store with food for the larva a single cell or several cells, which 

 may be made of clay or hollowed out in wood. 

 They then deposit one egg in each cell and seal 

 it up, repeating the process later. A minute drop 

 of the poison is injected into each cell before the 

 latter is sealed. The formic acid which it contains 

 acts as an antiseptic and prevents the fermentation 

 of the sugar. The social forms also rear their young 

 in cells, but these are massed together in large 

 numbers and do not remain sealed up, the workers 

 going round from time to time and feeding the 

 larvae, just as warders feed the prisoners in a 

 cellular prison. The wax of which these masses 

 of cells or " combs " are made is secreted by 

 glands situated on the inner face of the ventral 

 plates of the abdominal segments. The wax 

 appears in the torm of thin plates which are re- 

 moved by 1 the hinder pair of legs and then 

 " worked up " by the mandibles. Many species 

 are parasitic in the hives of more industrious forms. 



Sub-fain. 1. Archiapinae. Proboscis short with concave-margined 

 free end ; very few hairs, but these are plumose ; posterior legs un- 

 modified. This archaic group includes the genus Prosopis (some 

 add to it Sphecodes) which builds its nest in bramble-stems or 

 crevices in walls. There are ten British species. 



Sub-fain. 2. Obtusilinguinae. Hairy, with hairy second and 

 third legs adapted for carrying pollen ; ligula short and bilobed. 

 Colletes, with six British species, digs holes in the ground and divides 

 the burrow into a few cells which it fills with fluid food. Sphecodes 

 seems to be a genus in a very plastic condition, for there is such vari- 

 ation in form as to make specific differences a matter of great 

 difficulty. Its habits, sometimes industrial, sometimes parasitic, are 



equally lacking in precision 

 and its position in any 

 classification is uncertain. 



Sub-fam. 3. Andreninae. 

 Ligula short, with acute tip ; 

 gregarious bees, the cells 

 made by one individual con- 

 nected by passages with those 

 made by others. Halictus 

 makes oval, underground 

 cells lined with a varnish 

 which is probably produced 

 by the salivary glands. An- 

 drena is a large genus with 

 some fifty British species. 



They live in sandy and gravelly soil. Dasypoda also burrows 

 in loose earth, making tunnels of one or two feet in length. 



Sub-fam. 4. Denudatinae. Parasitic and without any modifications 

 for carrying pollen. The bees classed together here have little in 

 common beyond their parasitic habits. Stelis lays its eggs in the 



FIG. 495. Sphecodes gibbusl . Britain. From Sharp. 



