INSECTS. 



into moulds, in which shape it is exported to all parts of the empiri It 

 is used for candles and also as medicine. It would seem that the natives 

 of the central provinces did not find it profitable to reserve a portion of 

 the insects to use in starting the next year's crop, but find it cheaper to 

 import them from the southeastern districts. The wax is crystalline and 

 dazzling white, and in its chemical nature it is a cerotic ether. 



The plant-lice, or aphides, which swarm upon vegetation, come a step 

 higher in the scale, and in their habits 

 there are several points of interest. We 

 have already alluded to them as being the 

 cows of the ants, and Linnaeus speaks of 

 ' Aphis vacca formicarum ' — aphis the cow 

 of the ants. They have two slender tubes 

 projecting from near the tip of the abdo- 

 men through which they can secrete at will 



. . , , . . Fig. 234. — Winged stage of the plant-louse 



a sw»eet mice — the honey-dew ot which (Aphis), compare with the wingless forma 



- -, d shown in Figure 222. 



the ants are so fond. 



As usually seen, the plant-lice are fleshy, wingless forms (Fig. -'22) 

 which slowly wander over the plants, puncturing the tissue here and there, 

 and greatly weakening its vitality, if not completely destroying it. At 

 times, however, winged forms are seen, and these facts have a peculiar 

 explanation. The elucidation of the story is due to Bonnet, a Swiss natu- 

 ralist who lived in the last century. He separated one of these wingless 

 forms, and carefully watched it for months, noting its every change, and 

 recording every molt. One day it surprised him by giving birth not to 

 an egg, but to a living young ; the next day it was the same, and so on — 

 some days, one young, some days, several — until at last the total number 

 amounted to ninety-five. These young grew up, and in their turn became 

 mothers, and this without the intervention of any males. So it went on 

 through the summer ; generation after generation appeared, and it was 

 not until the autumn that the perfect insects — male and female, the 

 former winged — appeared. These laid eggs, which were to remain through 

 the winter, and then in the spring reproduce the species. 



One of these aphid-like forms, the Phylloxera, is to be enumerated 

 among the extremely injurious insects. It first acquired prominence in 

 the vine-growing regions of France, where, for several years, .the vines had 

 been injured and killed, no one knew by what. At last the government 

 took the matter in hand and offered rewards for practicable remedies, and 

 in 1868 it was shown that the Phylloxera was the cause. This was 

 step, for one must know the cause before he can intelligently apply th 

 remedy. It was found that there were two types of the insects. — 



