l82 



Marvels of Insect Life, 



if we may take Girard's observations of anotfier Brazilian species ^ as applying to 

 the genus. He says the brood-cells are provisioned with pollen and honey before 

 the egg is laid, and that when the queen has supplied this item, the cell is sealed 

 up at once, the resulting grub pursuing its course of development without being 

 attended by nurse-bees, as is the case with the honey-bee. Unfortunately, what 

 goes on in the closed nests of these mosquito-bees is so little known that one cannot 

 be sure that the various species agree in this respect, though it is very probable 

 that they do. 



The Senses of Insects. 



There are still, we fear, a considerable number of people to whom the mention 

 of senses in Insects must appear to be the purest nonsense. Believing that it is 

 derogatory to man's status as the " lord of creation " to concede the possession of 



intelligence to the lower animals, Insects are 

 considered by them to be mere automata 

 moved by instincts, and, therefore, not in 

 need of senses. Perhaps, also, there may 

 be a difficulty in believing that it is possible 

 to crowd into such minute bodies the 

 ^^^^^1^ ■' >^^ ^[^ -^"^^EV organization that is necessary for the develop- 



^^J^^^^HK-' '^^'•^S^nS^^VV ment and exercise of sense. That Insects 



""^^^^HB^ .^"^BPw^^^ ^^^ ^^^ quite so plentifullv provided with 



^*- ^^^^^ ^m.-\\ different senses as man mav be admitted, 



,^ , ^^^^mi%_^^^^^ma perhaps ; on the other hand, there is reason 



1^ ^ <H^r^^^ t^^^Mm ^^^ believing that those thev have are liner 



than the corresponding ones that we possess. 

 We have already mentioned that Insects 

 are endowed with a highly organized and 

 complex nervous system, and with this the 

 special organs of sense are, of course, linked 

 up. Let us glance at these sense-organs in 

 turn. 



First let us take the eyes, the organs of 

 vision, as these are usually very prominent features of the Insect. These 

 are of two kinds, the simple eye and the compound eye. The simple 

 eyes are not so well known to the casual observer as are the large comi)()und 

 eyes. They are situated, as a rule, at the top of the head, and are usually 

 three in number, arranged in triangular fashion. All Insects have not got these 

 simple eyes ; nor have they all got compound eyes. The simple eye is very similar 

 to what have been called erroneously the eyes of plants. A portion of the outer 

 skin has become convex both above and below, and becoming transparent has formed 

 a lens. The cells of the lower skin immediately below this lens have also become 

 transparent, and thus allow light-rays that have (>ntered through the lens to be 

 transmitted to deeper-seated cells, which have been transformed into a retina. 

 Between the cells of the retina pass the rod-like ends of fibres of the ojUic nerve, 



^ Trigona scutellaris. 



Photo hy] [W. Ploma Youm;, F.R.M.S. 



Section of Compound Eye. 



The compound eye of the gad-fly is here seen in section, magni- 

 fied about thirty times. This enables us to see that the lenses 

 do not converge to a single point, and cannot give a combined 

 image. In some Insects one compound eye will consist of as 

 many as 27,000 of these lenses. 



as these are usually very 



