TRUE ORTHOPTERA 3167 



The Pediculina, or true lice, as distinguished from the bird lice of the order 

 Orthoptera, are provided with piercing and suctorial mouth parts, and live on the 

 blood of animals, to which by this means they are enabled to gain access. 

 Though they are without wings, and were at one time associated with other wing- 

 less insects in a separate order, lice are now generally regarded as degraded forms 

 of Rhynchota, in which the wingless condi- 

 tion has been brought about as an adaptation 

 to their parasitic life. In these insects the 

 head is set horizontally, and carries short, 

 cylindrical, and usually five- jointed antennas; 

 the eyes are small and simple; and the mouth 



I. HEAD LOUSE WITH ITS EGGS; 2. BODY LOUSE ; 



consists externally of a soft, retractile beak, 3 . C RAB LOUSE. (AH greatly enlarged.) 

 somewhat conical in shape, and furnished be- 

 low with a row of hooks for attachment. Within the fleshy beak there are four 

 grooved pieces, forming by their juxtaposition an inner membranous tube, which 

 can be extended beyond its sheath, and acts both as a piercing organ and as a con- 

 duit for the passage of the blood which is sucked up by the insect. The thorax is 

 small and not distinctly divided into segments, while the abdomen is relatively 

 large, generally somewhat elliptical in outline, and exhibits seven or eight clearly 

 marked segments. The tarsi are two jointed, with the second joint in the form of 

 a claw which can be turned back toward the first. Lice multiply rapidly, one gen- 

 eration succeeding another in a short space of time. Their pear-shaped eggs are 

 generally found attached to the bases of the hairs; the young, which are hatched 

 after about eight days, undergo no metamorphosis, and, in some cases, require only 

 about eighteen days before becoming adult. 



Order THYSANOPTERA 



The insects comprised in this order some of them familiar enough to gar- 

 deners and others, by whom they are known as thrips are all small. A few species 

 only exceed four or five lines in length, while the great majority are less than a 

 tenth of an inch long. They are distinguished from all other insects by certain 

 peculiarities in the structure of their mouth and of their wings and tarsi. The 

 mouth lies far back on the under side of the head; its mandibles are transformed 

 into a pair of piercing setae, while the upper lip, maxillae and labium the two lat- 

 ter, provided with short palpi are united together to form a short suctorial tube. 

 The wings are small and narrow, contain few nervures, and are thickly fringed all 

 round with long hairs. Two pairs of such wings are generally present, but in some 

 cases they may be rudimentary or altogether wanting. The tarsi, which consist 

 of one, two, or three joints, are without claws at the end, but are furnished in- 

 stead with small vesicular lobes, by means of which they adhere to the surface 

 on which they rest. To these characteristics of the order we may add that the 

 body is narrow and cylindrical; the thorax is formed of three, and the abdomen 

 of ten segments; there are only three or four pairs of spiracular openings two on 



