312 



GLEANINGS IN BEE CULTURE. 



Mak. 1 



BREATHING-SYSTEMS IN INSECTS. 



We have it from good authority that ' ' man 

 can not live by bread alone." This is just 

 as true of insects. Indeed, oxygen may be 

 be said to be the most important food of all 

 animals. Even the muscles that we described 

 in our last paper, which, as we saw, are so 

 active and efficient in insects, can not work 

 without food, and no food is so immediately 

 important as oxygen. I mentioned in the 

 last article that the muscles of insects are 

 quicker to act, and stronger in proportion to 

 size, than those of any other animal, even 

 than those of man himself. We should ex- 

 pect, then, if oxygen is so important to feed 

 active organs, that the insect anatomy would 

 have this fact in view, and we should expect 

 the respiratory system to be in a very high 

 state of development. 



AIB-TUBES INSTEAD OF LUNGS. 



In insects we do not find lungs, though in 

 one of the groups of this great branch of an- 

 imals, the spider class, we do find lung-like 

 sacs for purposes of respiration. But in in- 

 sects, and so in our bees, we find lungs re- 

 placed by a very intricate and extended sys- 

 tem of air-tubes. In studying the anatomy 

 of insects, nothing is more interesting than 

 tracing this branching system of respiratory 

 tubes. 



There are two main tubes, one situated on 

 each side of the body, running lengthwise 

 from the head to the tip of the abdomen. 

 Short tubes at right angles to these main 

 tubes connect these with the outside of the 

 body, and at the outer end of these short 

 tubes are the several breathing-mouths, or 

 spiracles, which are often seen with the na- 

 ked eye. Any one who has closely noticed 

 the large green tomato caterpillar — larva of 

 the tomato sphinx — has noticed the large 

 spiracles on the side of the abdomen. These 

 are different in color from the body wall, and 

 so are quite conspicuous. It is easy to see 

 that they are openings to tubes. 



VALVES OF THE SPIRACLES. 



These spiracles are doubly guarded by 

 valves which prevent dust, etc., from enter- 

 ing the sensitive air-tubes. First there is a 

 hair valve, which acts as does the hair in our 

 own noses, to strain the air, if we may so 

 speak. Then there are muscular valves, by 

 the aid of which the insects can close these 

 tubes at will. In this respect the insects may 

 be said to be ahead of us, though we can 

 make our thumb and finger act as effectively 

 in guarding our own respiratory apparatus. 



The great lateral tubes already referred to, 

 as they pass lengthwise of the body, branch 



and rebranch, and thus reach intimately ev- 

 ery part of the body. These vessels at their 

 termination are very small, and under the 

 microscope are exceedingly beautiful and in- 

 teresting. 



STRUCTURE OF THE AIR-TUBES. 



What adds to the beauty of these air-tubes 

 is their peculiar structure. If we should take 

 a roujid stick and wind it closely with a fine 

 wire, and then remove the stick without dis- 

 turbing the wire, the wire would not be un- 

 like these air-tubes. This winding thread 

 can easily be seen when looking at the air- 

 tubes with a microscope; and if the tubes are 

 broken, as they always are more or less, we 

 always notice the waving thread reaching 

 out from the broken tube. Of course, there 

 is an epithelial lining to this spiral thread. 

 This epithelial lining is made up of cells, 

 and it is the function of these cells to take 

 the oxygen from the air in the tubes to the 

 blood of the body of the insect, and at the 

 same time to remove the carbon-dioxide from 

 the blood to the air-tubes when it is passed 

 off. This arrangement of cells and their ac- 

 tion does not differ from that which takes 

 place in our own lungs. It is simply osmo- 

 sis, which term refers to the passing of liq- 

 uids or gases thi'ough an organic membrane 

 when such membrane separates those of a 

 different character. In our own lungs the 

 osmosis is very rapid, and the extent of the 

 membrane is something tremendous. In the 

 great spread of membrane in our lungs Na- 

 tui'e has shown her disposition to do the best 

 to keep us alive and well. If we would al- 

 ways be as careful to provide good ventila- 

 tion by open doors and windows in our 

 sleeping-rooms, or, better still, by sleeping 

 out of doors, as we do, many of us, practi- 

 cally, here in California, there would be 

 much less of ill health and trouble in this 

 world than we find to-day. The insects 

 have even a more remarkable spread of 

 membrane, and nearly always sleep out of 

 doors, and we can not wonder at their 

 sprightly activity and apparent vigor. The 

 work done by our bees is really stupendous, 

 and puts in the shade the labor of the most 

 strenuous of our kind, and so we may well 

 rejoice at the admirable breathing apparatus 

 of our pets of the hive. We have all noticed 

 how admirably the bees ventilate their hives. 

 We have our patent ventilators. The bees 

 need no patent, for their method of ventila- 

 tion, as they fan at the hive entrance, leaves 

 little to be desired. We also have noticed 

 how quickly the bees die if the free air is 

 shut away from them. 



One practical point is worth mentioning 

 here. The bees ventilate so effectively, as 

 they fan at the hive entrance, that it is found 

 entirely unnecessary to arrange for any 

 further ventilation. It is, without doubt, 

 best to have only the one opening to the hive. 

 In the bee-tree or rock cavity the bees have 

 but this one opening, and yet from their 

 great activity they must have great drafts of 

 pure air, and so they have developed their 

 ventilating habit, which is very perfect. 

 Without doubt we serve them best when we 



