404 EXTERNAL ANATOMY OF INSECTS. 



greater portion of its lateral superficies, is an eye/ composed of 

 an immense number of highly convex lenses ; between these, 

 which are termed oculi, and nearly on the crown of the head, 

 are three simple eyes, called ocelli,^ very minute, and each con- 

 sisting of a single lens ; these are generally placed in a triangle, 

 and, like true eyes, are firmly fixed in the surface of the head. 

 In front of the ocelli, between the ociili, and attached by a 

 moveable articulation to the head, are the antennae, or prin- 

 cipal feelers. These are exceedingly various in size and form, 

 which depend almost wholly either on the habits of the 

 animals or on the development or situation of the eyes. In 

 nocturnal insects, and those diurnal ones which have either 

 small or very lateral eyes, the antennce are always of great size, 

 and in walking insects are carefully stretched forwards and 

 used to touch and ascertain the surface before every step." 

 Those insects, on the contrary, which only fly in the brightest 

 light, and which continue on the wing for a great length of 

 time without alighting, have enormous eyes but very small 

 antennce.^ Even in instances where the female in nocturnal 

 insects is sedentary and less active than the male, the antennae 

 of the latter are so much the more developed that little simi- 

 larity can be traced between them.' The mouth of insects at 

 first sight appears rather complicated ; it is composed of seven 

 pieces, which may be readily understood by an analogical 

 reference to the mouth of vertebrated animals — for instance, 

 man himself — bearing in mind that the parts of the mouth in 

 insects are to be considered and treated of as bones, the soft 

 and fleshy parts being internal. Suppose the upper and under 

 maxillary bones in man to be divided vertically down the centre, 

 leaving the lips entire, then suppose additional muscles given 

 to these jaws, so that they might move horizontally instead of 



s Not always present, as in the instance of the/co, which has only simple eyes, 

 or ocelli, a circumstance which renders its situation in a natural system very 

 difficult to ascertain. As far as I recollect, this very obvious and highly im- 

 portant character has not been noticed by any of our writers on this singular 

 animal. 



* Not always present, nor uniform in number. 



" Examples — Phnjganen, Carabus, Ceramby.i; Formica. 



^ Examples — Syrphus, LibeUida. 



y Examples — The Apterous females of Bombyces, and the'slothful females of 

 Mdolontha: ; while the closely allied genera Trichitts and Cetonia, both sexes of 

 wliich fly by day, have small and similar unicima:. 



