192 TRANSFORMATIONS OF INSECTS. 



twelfth of an inch long. They have no less than eighteen joints 

 in their antennae, and they deposit a quantity of eggs inside many 

 species of caterpillars. 



After having lived in the juices of the caterpillars, the larvae 

 of the Microgastcrs having attained their full growth, begin to 

 devour the viscera also, and finally they eat through the skin. 

 They then spin silky cocoons, and undergo their metamorphosis. 

 One of the species, Microgaster glomeratits^ which is black in colour, 

 and which has fawn coloured legs, can be recognised easily, and its 

 metamorphosis examined. The caterpillars of the cabbage butter- 

 fly, Pieris brassiccB, are frequently killed by this little parasite, 

 and occasionally nearly every one of these destructive vegetable 

 feeders falls a prey. They usually live until about the time of the 

 first metamorphosis, and then they begin to look out for a safe 

 place to hang themselves up, and to undergo the transformation 

 into the chrysalis state. But it is just then that they die, for then 

 the Microgastcrs which have had enough of the caterpillar, pierce 

 through its skin, and form their cocoons on and around it. They 

 complete their metamorphosis in a few days, and the perfect para- 

 sites fly. The cocoons of these Microgastcrs are usually united 

 in packets, are oval shaped, and being composed of very fine 

 yellow silk, look like those of silkworms in miniature. The 

 smallest of the ichneumons are the species of the genus Hyhrizoii, 

 and they wage war against the Aphides, one of them laying its 

 ^gg in the Aphis, which is so common on the delicate stems of 

 roses. 



The ProctotrnpidcB are distinguished from the Ichncumonidce 

 by their oblong body, the simple condition of the nervures of the 

 wing, the moderately long antennae, and the long pendant palps. 

 They are such little insects that they must be examined with a 

 good lens or a microscope, if they are to be studied. One tribe of 

 them attacks the maggots of flies, especially of the wheat fly, and 

 another lays its eggs in the larvae of the Tip7il(c — the daddy long- 

 legs tribe. Some of the parasites of the maggots spin cocoons 

 beneath the skins of their victims. The Tclcas ovulornm is a tiny 

 insect of about a fiftieth of an inch long, and it lays its eggs in 

 the eggs of moths, and when its larvae are developed they enjoy 

 their curious and small habitation. 



