THE ORGANS OP THE SENSES. 291 



1 . Ortkoptera collectively, without Forficula. 



2. Dictyotoptera, Libellula, and Ephemera, have three simple 

 eyes, Termes but two. 



3. Hemiptera. The majority of bugs have two simple eyes ; 

 some, for example, Lygceus apterus, none. The majority 

 of Cicada have three simple eyes ; some, for example, 

 Membracis, Plata, but two. The water bugs, as Nepa, 

 Ranatra, Naucoris, Nolonecta, Sigara, display no simple 

 eyes. 



b. Of insects with a perfect metamorphosis : 



1. The Diptera. Generally three, seldom two (Mycelophila) 

 simple eyes. The Tipularia, Culicina, and Gallifica, are 

 excepted, as they possess no simple eyes. 



2. The Lepidoptera. Two simple eyes in the crepuscular 

 moths and Noctuce (perhaps in all?) 



3. All Hymenoptera have three simple eyes upon the vertex 

 (some neuter ants are blind, as well as the majority of 

 larvae). 



4. Neuroptera. Three simple eyes as well as compound ones 

 in Phryganea, Semblis, Raphidia, Panorpa, Osmylus. 



5. Coleoptera. Two simple eyes in Onthophagus, Omalium, 

 and Paussus. 



III. Insects with merely compound eyes. 



a. All Coleoptera, with the exception of the above-named genera, 

 Anthophagus, Omalium, and Paussus, the two points upon 

 whose vertex are supposed to be simple eyes. 



b. Besides, several already-named genera and families of other 

 orders, as, Machilis, Forficula, Hydrocorides, Tipularia, 

 Culicina, Gallifica, Hemerobius, Myrmecoleon, Ascalaphus, &c. 



c. The larvae of insects with an imperfect metamorphosis. In 

 the larvae of the Cicada and Gryllus, the simple eyes are indi- 

 cated by spots, and the compound ones have fewer facets than 

 in the imago. 



With respect to the internal structure of the simple eye, there is 

 found beneath the very smooth hemispherical, or, at least, convex 

 transparent horny integument, a small globular transparent lens, which 

 lies closely attached to the horny integument, and fits into a corresponding 

 cavity in the inner surface of that integument. Behind the lens lies a 

 truly lens-shaped glassy body, larger in compass than the lens, corre-. 



u2 



