HARDWICKE'S SCIENCE-GOSSIP. 



229 



ful, as those of the silkworm, the cochineal insect, 

 and a few which are eaten as food. The cochineal 

 insect lays several thousand eggs on the cacti. An 

 insect which deposits its eggs on the most forward 

 of the figs hastens their ripening. Fig-growers have 

 for ages taken advantage of the habits of Blastophaga 

 grossonim for cross-fertilising the cultivated fig with 

 the wild Caprificus. 

 [ Some fifteen or twenty years ago a very large trade 



in width and depth. Each case contained some 600,000 

 eggs, attached to strips of cardboard, separated by 

 layers of tissue paper. From twenty to twenty-five 

 of these cards were placed in each case ; the cards 

 contained about twenty-eight grammes of eggs, or 

 from 30,000 to 35,000 ; each card was valued at 1/. 

 The silk-moth in Japan lays about two hundred eggs. 

 The silkworms' egg is the size of a pin's head, and is 

 of great commercial value. When first laid the eggs 



,'V-r *r ^3 V-* _- 



Fig. 134, — Egg of Magpie Moth. 



Fig. I35-— Egg of Red Admiral. 



Fig. 133.— Egg of Pieris brasskcc. 

 Jk-l 



Fig. 136. — Egg oi Polyommatus corydon. 



* ? ; 



Fig. 137.— Egg of Buff-tip Moth. 



%1 «l^%llfe: 



Fig. 138. — Egg of Meadow-Brown. 



Fig. 139.— Egg of ! 



[ Copper. 



Fig. 140.— Egg of Cabbage Moth. 

 (All magnified.) 



was carried on in importing silkworms' eggs, on 

 cards, from Japan to France and Italy, in con- 

 sequence of the silkworm disease. In the eleven 

 years ending with 1872, about two million pounds of 

 these eggs were imported to each of these countries, 

 costing over ten million pounds sterling ! In 

 December 1879, a consignment of silkworms' eggs, 

 filling six freight cars, arrived at New York from 

 Japan, via. San Francisco. The eggs were packed in 

 cases measuring three feet in length by about one foot 



are of a clear jonquil yellow, and if they are pierced, 

 will pass successively through a series of tints till 

 they arrive at their definite hue, an ashy grey ; while 

 if not pierced they will remain yellow. As the shell 

 or covering is nearly transparent, these changes of 

 colour, which are those of the germ which it encloses, 

 may be successively watched. From experimental 

 researches which have been made, it is found that the 

 hatching may be retarded or advanced by regulating 

 the temperature :— I. To prevent the eggs hatching 



