Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/680

646 the great charters ; and Hemingford s versions have more than once supplied deficiencies and cleared up obscurities in copies from other sources.

1em  HEMIPTERA (i?/xi-, half, and irrepov, wing), an order of the Insecta most commonly known by the name of &quot; bugs, &quot; and containing the species so well known to infest houses. In their earlier stages they have what is known amongst naturalists as an incomplete metamorphosis; that is to say, after quitting the egg, and during the two stages of their existence before assuming the perfect form, they move freely about, thus unlike the Lepidoptera, &c., whose pupa state, or that preceding the perfection of the insect, is quiescent. When the transformations have been completed, the insect generally possesses four wings. The superior pair, or hemielytra as they are called by authors, are attached to the mesothorax, and are composed of two substances, the basal portion coriaceous, or resembling leather, and the apical one membranaceous, or resembling thin, transparent parchment. The lower pair are attached to the metathorax, and are entirely membranous and generally transparent, and capable of being folded when the insect is in repose. This segment of the sternum likewise bears on each side, anteriorly, a more or less reniform-shaped orifice, within which lies a sac containing the fluid or matter from which so many of the Heteropterous portion of the order emit a most disagreeable odour. They also possess in all stages a mouth (rostrum) composed of three or more joints formed for suctorial purposes.

1em

Although the Hemiptera are of very ancient date, remains of some of the fossil forms having been found in the Primary and other formations, the number of these is but few ; they are enumerated in a paper on &quot; Fossil Entomology&quot; by Mr H, Goss in vol. xv. of the Entomologist 1 s Monthly Magazine. {{ti|1em|The whole of the group is extremely widely distributed, being found in almost every portion of the globe; and they are very varied both in form and in their modes of life, man, animals, birds, insects, and plants being subjected to their attacks. On the Continent they have for a long period engaged the attention of naturalists, but in England little was known of the actual number inhabiting these islands until Douglas and Scott in 1865 published their volume of British Hemiptera-Heteroptera. In 1859 Dr A. Dohrn published what may be considered to be the first whole- world catalogue of the order ; and, taking it as a basis, for there is no other approximate list, and adding a reasonable amount of new species collected in each year since that time, their number would amount to nearly 10,500 species, 5300 belonging to the heteropterous section and the remainder to the second sub-order. Out of these Europe lays claim to at least 3000, whilst Great Britain is known to possess not fewer than 1000. There is no record of any one of the species being cosmopolitan (except perhaps the house bug, Acanthia lectularia}, although some of the species inhabiting England are also to be met with in CLina and Japan.}}  HEMLING. See.  HEMLOCK is the Conium maculatum of botanists, a biennial umbelliferous plant, found wild in many parts of Great Britain and Ireland, where it occurs in waste places, on hedge-banks, and by the borders of fields, and which is also widely spread over Europe and temperate Asia, and naturalized in the cultivated districts of North and South America. It is an erect branching plant, growing from 3 to 6 feet high, and emitting a disagreeable smell, like that of mice. The stems are hollow, smooth, somewhat glaucous, green, spotted with dull dark purple, as alluded to in the specific name, maculatum. The root-leaves have long furrowed footstalks, sheathing the stem at the base, and are large, triangular in outline, and repeatedly divided or compound, the ultimate and very numerous segments being small, ovate, and deeply incised at the edge. These leaves generally perish after the growth of the flowering stem, which takes place in the second year, while the leaves produced on the stem become gradually smaller upwards. The branches are all terminated by compound 