152 THE NORTHERN MICROSCOPIST. 
not increase in size. All true insects have six legs when they have 
attained their perfect form. Sometimes a casual observer might 
doubt this, for only four are observable, but if careful search is 
made two others of a rudimentary description will be found. The 
Fig 25. 
antenne or “feelers” may next be noticed, for they frequently give 
‘great character to the appearance of the insect. In some beetles 
they are slender and long, as in the Dy#tscus marginalis, but in 
others they are short and club-shaped. Dytiscus marginalis, being 
a beetle, belongs to order ‘‘Coleoptera,” because it has very 
strong leathery wing-cases, useless in flight, but serviceable in pro- 
tecting the true wings from injury. These are termed Elytra, and 
when exhibited under polarized light make a pretty object. 
We may now glance at the anatomy of a beetle. Any beetle 
will answer the purpose. Beginning with the cephale or head, the 
first portions which we notice are the mandibles, which will be seen 
to be a formidable pair of forceps, calculated not only to seize but 
to hold the prey when it is seized. The next are the antennz, 
consisting of two parts, the scage and the club. ‘This appendage 
undergoes various modifications in the different beetles, but the 
general structure remains the same. Again, we have the /adzal palpi, 
or lip-feelers, and the maxtllary palpi, or jaw-feelers ; the anterior © 
pair of legs, consisting of the ¢arsz, or feet, the “#d¢a, or shank, and 
the femur, or thigh; the portion by which the femur is united to 
