GLOSSARY 277 



Coleoptera. Or Beetles, a vast order of insects, characterised, as the 

 name implies, by the structure of the first pair of wings, or elytra 

 as they are called, which are more or less horny, forming sheaths 

 for the protection of the under wings the true organs of flight in 

 these insects. 



Composite. Plants the inflorescence of which consists of very numerous 

 small flowers (florets) arranged upon a common receptacle, and 

 crowded into a dense head (capitulum}. The Daisy is a common 

 example. 



Concentric. Having one common centre. 



Congeries. A mass of small bodies. 



Crop. A dilation of the oesophagus in insects, serving as a reservoir of 

 food See gullet. 



Dimorphic. Having two dissimilar forms. 



Dimorphism. The condition of the appearance of the same species 

 under two conspicuously distinct forms. 



Diicdons. The term is applied to species which have the organs of the 

 sexes upon different individuals. 



Dipt era. Or Flies two- winged comprise insects with only two 

 wings, minute club-shaped organs, called poisers or halteres, taking 

 the place of the hinder pair 



Dorsal. Of or belonging to the back. Relating to the back, or 

 posterior surface of the body, as opposed to the ventral or anterior 

 surface. 



Elytra. The forewings of Beetles and Earwigs. They are thick, horny, 

 or leathery, and serve as cases or sheaths for the membranous hind 

 pair of wings, which constitute the true organs of flight. 



Embryo. The voung insect in course of development within the egg. 



Ephemera. A group of Neuropterous Insects allied to the May Fly. 



Epidermis. The superficial layer of the skin, as opposed to the deep 

 layer the true skin. 



Epiphytal. Many tropical species of Orchids are called epiphytal that 

 is growing in the air, attached to the trunks of trees. Their aerial 

 roots do not reach the soil, they cling to the bark, and ai'e greenish 

 or white. These Orchids derive no nutriment from the tissues of 

 the plant on which they grow, but absorb moisture from the air, 

 and from what trickles down the tree, containing decaying organic 

 and inorganic matter. 



Excentric. Removed from the centre or axis. 



Exotic. Foreign, not native, the opposite to indigenous meaning 

 native to a country. 



Exuvia. Cast-off skin. 



Exuviation. The process by which animals shed or throw off their old 

 coverings, skins, &c., and assume new ones. 



Eyes, compound. These are situated one on each side of the head, 

 and are of considerable size, and attain a marvellous degree of 

 complexity. Under a microscope they have a honey-comb like 

 appearance. Each of the little six-sided divisions is in reality a 

 distinct eye, or lens, so that these eyes are compound, or composed 

 of many separate small eyes or ocelli placed side by side ; some- 



