168 INSECTS AT UOME. 



Elencfius tenuicornis, each compound eye only contains fifteen 

 facets or lenses. 



The anteunaD are very remarkable, bein<^ doubly branched, 

 BO that the insect seems to have four antenna; instead of two. 

 These little insects fly well, the second pair of wings being 

 enormously large in proportion to the body, and opening like 

 a wide fan, the anterior and posterior margins reaching to the 

 hf-ad and tail of the insect. When flying, the Stylops has a 

 peculiar milky look about the wings, not easy to describe, but 

 easily to be recognised when once seen. Wings of such mag- 

 nitude necessarily require a very large thorax, in order to give 

 support to the muscles which move them ; and accordingly we 

 find that the thorax is nearly twice as large as the head and 

 abdomen togetlier, the latter part of the insect looking quite 

 insignificant when compared with the enormous thorax to 

 which it is attached, and of which it almost seems to be an 

 unimportant appendage, instead of being, as it is, the seat of 

 the chiefly vital organs. 



As might be expected, the part of the thorax which bears 

 the hind pair of wings, namely, the metathorax, is very largely 

 developed, while that which bears the little attenuated elytra 

 is comparatively small. These members are indeed so small, 

 that they have been called pseudelytra, or false elytra. Many 

 species of bees and wasps are infested with this singular para- 

 site, though the genus Andrena seems to be its favourite prey. 



With two more examples of the Heteromera, we close our 

 notice of this group. One is the Blister Beetle or Spanish 

 Fly (^Lytta vesicatoHa), which is shown on Woodcut XVI, 

 Fig. 3. This insect is well kno-vvn for its use in medicine, the 

 peculiar substance contained in it being highly inflamma- 

 tory, and raising blisters upon the human skin. This sub- 

 stance is called cantharidin, and, when separated from the in- 

 sect which produces it, takes the form of white flat crystals, 

 which can be dissolved in alcohol, but not in water. 



This genus is known by the long narrow body and elytra, 

 the two long wings, and the egg-like form of the last joint of 

 the maxillary palpi. The colour of the Blister Beetle is rich- 

 green, mostly glossed with gold or copper. The elytra are very 

 slightly wrinkled, and upon eacl: elytron there are twc .'idges. 



