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TEXT-BOOK OF ENTOMOLOGY 



c, c' approach each other. The arms of the Y straighten and shorten, so that 

 the sheath and darts are driven from their hiding-place together and the thrust 

 is made by which the sheath produces its incision and fixture. The sides being 

 symmetrical, we may, for simplicity's sake, concentrate our attention on one, say 

 the left in the figure. A muscular contraction of a broad strap joining k and d 

 (the dart protractor) now revolves k on I, so that a is raised, by which clearly c 

 is made to approach d; i.e. the dart is sent forward, so that the barbs extend 

 beyond the sheath and deepen the puncture. The other dart, and then the 

 sheath, follow, in a sequence already explained, and which G, Fig. 195, is in- 

 tended to make intelligible, a representing the entrance of the sheath, ft the 

 advance of the barbs, and c the sheath in its second position. The barb re- 

 tractor muscle is attached to the outer side of i, and by it a is depressed and the 

 barbs lifted. These movements, following one another with remarkable rapidity, 

 are entirely reflex, and may be continued long after the sting has been torn, as 

 is usual, from the insect. By taking a piece of wash-leather, placing it over the 

 end of the finger, and applying it to a bee held by the wings, we may get the 

 fullest opportunity of observing the sting movements, which the microscope will 

 show to be kept up by continued impulses from the fifth abdominal ganglion and 

 its multitudinous nerves (n, Fig. 194,^4), which penetrate every part of the sting 

 mechanism, and may be traced even into the darts. These facts, together with 

 the explanation at page 49, will show why an abdomen separated many hours 

 may be able to sting severely, as I have more than once experienced. 



The male genital armature in the bees is originally composed of 

 three pairs of tubercles, homologous with those of the female, all 



originally arising from three 

 abdominal segments, two after- 

 ward being anterior, and the 

 third pair nearer the base of the 

 abdomen. 



The ovipositor of the dragon- 

 flies (Odonata) is essentially like 

 that of the Orthoptera and 

 Hymenoptera. Thus in JSschna 

 (Fig. 196), Agrion (Fig. 196, C), 

 and also in Cicada it consists 

 of a pair of closely appressed 

 ensiform processes which grow 

 out from under the posterior 

 edge of the eighth uromere and 

 are embraced between two pairs of thin lamelliform pieces of similar 

 form and structure. 



The styles and genital claspers (Rhabdopoda). Other appendages 

 of the end of the abdomen of pterygote insects, and generally, if not 

 always, arising from the ninth segment, are the clasping organs, 

 or rhabdopoda as we may call them, of Ephemeridae (Fig. 197), 

 Neuroptera (Corydalus [Fig. 198], Myrmeleon, Khaphidia), Trichop- 



FIG. 196. A, rudimentary ovipositor of 

 nymph of ^Eschna. J3, the corresponding tf 

 structures ; a, enlarged. C, ovipositor of nymph 

 of Agrion ; d, pill. 



