i6o 



HA R D WI CKE ' S SCIENCE- G OS SIP. 



the most of this fine spring, that has given us less 

 ram and more sunshine than anyone seems to 

 remember. I saw on March 9th a very fine speci- 

 men of brimstone butterfly, and was pointing it out 

 to a person that was with me, when a blue titmouse 

 darted from a tree, gave chase to the butterfly, and 

 snapped it up. I had not seen this done before. 

 Caterpillars of the tiger-moth were, the second week 

 in March, plentiful ; very shortly whites, both large 

 and .small, made their appearance ; tortoiseshells of 

 both species, also the painted lady, which, by the 

 way, are not very highly painted, a great deal of the 

 painting appears to be rubbed off from early speci- 

 mens. I consider all earlies to be hybernated 

 specimens ; the peacock, meadow-browns, and some 

 ringlets, and two species of blues, which, I believe, 

 were the common blue and the holly blue ; all this 

 number were seen by me at the end of the third week 

 in April. A great number of moths also made their 

 appearance earlier than usual this 'spring. But the 

 cinnabar moth being a day-flier, is very conspicuous 

 among them, and I never fail to note its appearance. 

 I have such dates as May 10th, 12th, 13th, 14th, 

 16th, &c, this year ; I saw three on the morning of 

 April 15th, and have seen them nearly every day since 

 that date. The fine, dry spring would seem un- 

 favourable to the helices, but they are very plentiful, 

 and take advantage of damp evenings and the little 

 showers we have, for getting abroad. I was in a 

 rather neglected ■ garden one evening after a shower, 

 early in May ; I found H. nemoralis so plentiful on 

 the "gooseberry-trees, it appeared that the one 

 object of the trees must be to produce snails, about 

 forty various forms were secured in a quarter of an h6ur. 

 Speaking of trees reminds me of other trees ; many 

 plum-trees, in sheltered situations here, have very 

 large crops of fruit, and one tree that I know, which 

 is trained to a wall, has a large crop of plums ; and 

 on this same tree there are about twenty twins or 

 doubles — two plums growing on one common stalk — 

 in some cases they are united, in others they are dis- 

 tinctly separate. I am very much connected with 

 fruit and fruit-trees, but I do not remember seeing 

 anything like it before. 



Hy. Blabey. 



THE SENSES OF INSECTS. 



By W. H. Seyfang. 



IGHT.- — The eyes of insects are situated in the 

 v_J head, and are generally (in the adults) five in 

 number ; two large compound eyes (oculi), and 

 three small simple eyes (ocelli). The occuli are 

 placed on the sides of the head, and the ocelli 

 generally above and between them. Each oculus is 

 made up of a large number of hexagonal facets ; of 

 these the house-fly has about seven thousand in each 

 eye, and a butterfly, over seventeen thousand. It 



might be inferred that every object presents to an 

 insect a multitude of images, but as we are not in 

 the habit of seeing double, I should think that the 

 nerves supplying each facet join up to form an optic 

 nerve, which perhaps carries one impression to a 

 retina. Muller says of an insect's eye, that " each 

 individual facet of the compound eye can survey but 

 a small 'space in the field of vision, each only con- 

 tributes to the perception of all things within it. 

 Each separate one does not at the same time see all 

 such objects, but conveys its impression to the 

 nervous filament with which it is supplied, and the 

 latter being united in the great optic nerve, a 

 common and distinct image is ultimately produced." 

 Of eyelids insects are wholly destitute, but the cornea 

 in some is covered with hairs to keep the eye free 

 from dust or other obstacles. Insects are not long- 

 sighted, but the eyes of some are beautifully adapted 

 to their mode of existence. In the whirligig beetle 

 {Gyrinus natator), for instance, the two oculi are 

 divided into four, one pair to look upwards through 

 the water, and the other downwards. 



In the size and number of the visual organs, insects 

 have the advantage over all the higher forms of 

 animal life, but in number they are surpassed by 

 some of the lower forms, such as some scorpions with 

 twelve, leeches with ten. 



Hearing. — Linnaeus doubted whether insects hear at 

 all. Other naturalists have thought that the antennae 

 are the organs of hearing. My own opinion is that 

 insects - perceive sounds by the sense of touch, that the 

 vibrations created by sound are communicated to the 

 antennae, but that the latter are organs of touch, not 

 of hearing. For instance, if a butterfly be resting on 

 the ground with the antennae outspread, and some 

 noise be made on the ground a few yards off, the 

 vibrations produced by this sound would be com- 

 municated to the antennae, and the insect would fly 

 away. It would not take long for the butterfly to 

 receive this warning, as sound travels at the rate of 

 about 1 142 feet in a second. Thus, the vibrations 

 which affect our organs of hearing would be, in an 

 insect, communicated to the organs of touch. 



Feeling. — The nervous system |of an insect consists 

 of a double ventral chain of ganglia (two ganglia in 

 each segment) united by commissures. The first two 

 ganglia are above the oesophagus, and are united 

 to the second two by commissures passing round the 

 cesophagus, and termed the oesophageal collar. 



The antennae are thought to be the principal 

 organs of touch, though some think them to be 

 organs of hearing, or perhaps smell ; but neither of 

 these two seems probable. In reference to the 

 question of an insect's feeling when injured, I fully 

 believe that they do feel it, although some author 

 quotes a case of a wasp which had been deprived of 

 its abdomen, regaling itself on some red syrup, 

 which gathered into a bead at the hinder end of the 

 thorax. If an ichneumon fly [pierces a caterpillar, 



