The Zoologist— June, 1868. 1233 



gul is very simple : it consists in preparing worms ready to spin by 

 putting them in strong vinegar for eighteen hours; a transverse 

 opening is then carefully made on the under side and about the 

 middle of the body, taking care not to injure the silk-reservoirs, which 

 are very distinct. The glands, or reservoirs, are theu taken out and 

 stretched parallel to each other on a board, and dried in the shade for 

 several days. 



The Enemies of the Silk-worm. — Birds are the most formidable foes 

 to the silk-worm, especially the thrushes, cat-birds and orioles. It is 

 probable that ninety-five out of a hundred worms become the prey of 

 these feathered insect-hunters. Toads and snakes also destroy some, 

 and mice, rats, moles and squirrels eat the chrysalis enclosed within 

 the cocoon. Among insects they have many enemies, such as various 

 spiders, ants, bugs and wasps ; but their most dangerous foe is the 

 Ichneumon fly. A Tachina-like fly also deposits its eggs in the body 

 of the larva. The Ichneumon flies can be seen in summer flying about 

 bushes in search of caterpillars in which to deposit their eggs; and 

 I have observed them often flying for an hour among shrubs where no 

 worms were feeding, for which they searched carefully, peering under 

 almost every leaf. When an Ichneumon detects the presence of a 

 worm she flies around it for a few seconds, and then rests upon the 

 leaf near her victim : moving her antennae very rapidly above the body 

 of the worm, but not touching it, and bending her abdomen under the 

 breast, she seizes her ovipositor with the front legs, and waits for 

 a favourable moment, when she quickly deposits a little oval white 

 egg upon the skin of the larva : she remains quiet for some time and 

 then deposits another egg upon the larva, which only helplessly jerks 

 its body every time an egg is laid on it : she thus lays some eight or 

 ten eggs, which adhere so firmly to the skin that it is very difficult to 

 take them off". After several days these eggs hatch out, and the small 

 white larvae may be seen at work as soon as they are out of the eggs, 

 digging their way under the skin of the worm, on whose fatty portions 

 they feed. The caterpillar, however, continues to eat and grow, and 

 lives long enough to make its cocoon ; but when once enclosed in it 

 the parasites which prey upon it have already eaten the fatty portions, 

 and now attack the vital parts of the larva, which they speedily con- 

 sume, and finally the one that outlives the others makes a cocoon 

 within that of the Polyphemus larva; but it is a remarkable fact that 

 here the maternal instinct of the Ichneumon fly makes a terrible 

 mistake : several of the Ichneumon larvae have entered the worm, but 



SECOND SERIES — VOL. III. 2 E 



