8 ENTOMOLOGICAL NEWS. [January, 



The upper line represents P. maadata; the lower, P. quadri- 

 signaia. The genus Psoa, although belonging to the Bostri- 

 chinae, resembles Trichodes in form, the elytra having a ground 

 color of blue or green, the markings yellowish to red. The 

 markings of quadrisignata are suggestive of Trichodes ornaius in 

 the fourth figure, while viaadata is rather of a vittate type. 



It is hoped that these notes and figures will be at least caution- 

 ary to those who see in slight differences of the metallic surface 

 lustre, or the extent of markings a sure indication of a new 

 species. 



o 



ELEMENTARY ENTOMOLOGY. 



Seventh Paper. — The Abdomen — Internal Anatomy. 



The third and last region of the body is the abdomen. The 

 abdominal segments are not so closely united to each other as 

 are the segments of the head and the thorax; they consequently 

 possess a freedom of motion between themselves not to be found 

 in the two former regions of the body. 



The abdominal segments sometimes receive the special name 

 of urites. Their typical number is eleven (Packard), but in 

 different insects varies from three to eleven. 



Besides the three pairs of jointed legs, situated near the front 

 end of the body, and which correspond to the (thoracic) legs of 

 the imago, many larvae have other thicker, fleshy legs, termed 

 prolegs, prop-legs, ox false legs. The prop-legs are not jointed, 

 and end in a circle of minute hooks; they are placed on that 

 part of the larva corresponding to the abdomen of the imago, in 

 which state they are not usually represented. The nymphae of 

 those insects which undergo only an incomplete transformation 

 have six jointed, thoracic legs. Of the larvae that undergo a 

 complete transformation, some have no legs, as maggots; others 

 have six jointed, thoracic legs; others still, as caterpillars, have 

 six jointed, thoracic legs, and from ten to sixteen jointless, ab- 

 dominal prop-legs. Some of those insects which do not pass 

 through any transformation have jointed abdominal legs; in this 

 particular they differ from the definition of an insect as given in 

 the first paper. 



^ In many insects which have an incomplete transformation, 

 there is in the nymph a pair of jointed appendages to the last 



