ARTICULATA. 139 



Insects whicli have five articulations to the tarsus are named i?enta- 

 meroiis. Those with four are named tetramerous ', but as a fifth immovable 

 and microscopic articulation has been discovered, Eurmeister names this 

 form cryptoiKntameTOus^ and Westwood, pseudotetramerous^ a useless 

 addition of names, for, as Mulsant observes, the terms Tetrojinera^ &c., 

 refer to the number oi free articulations. Sober goes so far as to consider 

 all the Coleoptera pentamerous ; but even could the abortive articulations 

 be detected, the relation of the difierent groups would not be altered, 

 because the tarsi of the Peutamera would still have five, and tiiose of the 

 Tetramera lour movable pieces. In the Hetero'^nera the four anterior tarsi 

 have five^ and the posterior pair yb7^r articulations, Trinierous^ dimerous, 

 and monomerous tarsi are also enunaerated. The anterior tarsi are some- 

 times wanting, as in Ateuchus. 



The wings, when present, are 'either two or four, the anterior pair being 

 affixed to the mesothorax, and the posterior ones to the metathorax. Some- 

 times the two pairs are equal, and when they are of unequal size, sometimes 

 the anterior ones are the largest, as in the Hjmenoptera and Lepidoptera ; 

 and sometimes the posterior ones, as in the Orthoptera. In the Coleoptera 

 the anterior wings are converted into elytra for the protection of the true 

 wings, not being used as organs of flight. The wings are composed of two 

 usually transparent membranes, between which various hollow nervures are 

 distributed, and filled with air from the body. In the Orthoptera (grasshop- 

 pers, &c.) the upper or anterior wings (named teg?m7ia) are thicker and 

 narrower than the inferior ones, and the latter are folded like a fan. In a 

 jDart of the Ilemiptera the base of the upper wings has a leathery texture. 

 All the wings of the Hymenoptera, Lepidoptera, and iSTeuroptera, are of a 

 uniform texture respectively. Those of the Lepidoptera are covered with 

 minute scales ; those of the Xeuroptera have numerous reticulating nerv- 

 ures, and in the Hymenoptera the nervures are but few. In the Diptera, or 

 flies, the anterior wings are used in flight, the posterior ones being reduced 

 to a small knobbed thread {hcdteres). In the Strejpsijptera the posterior wings 

 are fully developed, the anterior ones being abortive. In most of the 

 orders of winged insects there are genera and species which have no 

 wings; and some have wings in one sex and not in the other, as in the 

 female coleoptera, known as glowworms. In one genus of Orthoptera the 

 posterior wings are present, without a vestige of the anterior pair. 



Abdo'men. The abdomen is attached to the metathorax, either by its 

 entire breadth, or by a portion of it only. The upper surface is named the 

 dorsum, and the lower one the venter. Of the nine distinct normal 

 segments some are occasionally absent by a union of several into one. In 

 some cases the segments of the dorsum and venter do not correspond ; in 

 Carabus, for example, the former has nine and the latter but five. In many 

 cases the abdomen of the male has one segment more than that of the 

 female, and the dorsum has generally one more than the venter. The con- 

 nexion between the upper and lower parts of the same segment, and between 

 the segments, is eftected by a membrane, and in the latter case the base of 

 each segment slides within the preceding one. The abdomen is more 



343 



