WASPS 193 



There are two chief groups of wasps Solitary and Social- 

 distinguished by various structural features which need not 

 detain us, and also by habits and domestic economy. The 

 Solitary or mud-wasps construct small mud cells for the recep- 

 tion of their eggs, and provide a store of caterpillars for the benefit 

 of the grub. These caterpillars are paralysed, but not killed, 

 by the sting of the female, and remain in this helpless condition 

 until the growing grub devours them. Each female mud-wasp 

 works entirely alone, and, having constructed and provisioned 

 one or more cells in crevices in masonry, holes in posts, door- 

 locks, window-latches or other similar spots, takes no further 

 interest in her work and progeny. All these Solitary are smaller 

 than the Social wasps, and of a paler yellow colour ; moreover, 

 there are among them but two conditions of sex, perfect females 

 and males ; there are no " workers " (sterile females). On the 

 other hand, the Social wasps live in great communities, whose 

 members co-operate for the common welfare ; their nests are 

 constructed of wood-pulp (wasp-paper), and are either placed 

 underground or suspended from the branch of a tree, according 

 to the species ; each nest is founded by a perfect female (" queen "), 

 and her offspring alone form the population, which comprises 

 sterile females or (t workers," perfect females or " queens " 

 of the next year, and males or drones. It is these Social wasps 

 that are so commonly known, and to these we will confine our- 

 selves in considering the anatomy. 



The head carries a pair of large " compound " eyes, which 

 occupy the greater part of the right and left sides. Each eye is 

 shining and black in colour ; the margin nearest to the middle of 

 the front of the face is deeply notched, and the bay thus formed 

 is more or less, according to the species, occupied by a strip 

 of yellow colour. If examined under a magnifying-glass, the 

 surface of the eye is seen to be divided up into a large number, 

 many hundreds, of minute hexagonal areas (facets), each of 

 which is in reality the surface of one eye-element. These facets 

 are transparent ; the black appearance is due to dense masses 

 of dark pigment which surround the deeper parts of each under- 

 lying eye-element, and which prevent light that has entered 

 at one facet from reaching the sensitive portion of any other 



VOL. I. 13 



