52 Descriptive Zoology. 



site. A group of parasitic Hymenoptera (the Braconids) deposit their 

 eggs on the caterpillar ; the little larvae bore their way into the big 

 larvae, and after consuming the tissues of the caterpillar, eat their way 

 out and add insult to injury, attaching their cocoons to the outside of 

 the skin. Sometimes the chrysalid of a cabbage butterfly fails to trans- 

 form, and a hole may be discovered where the adult " Braconids " have 

 made their escape. 



Characteristics of Hymenoptera. The Hymenoptera 

 have two pairs of membranous wings, the hind pair being 

 smaller than the front. The mouth parts are fitted both 

 for biting and for sucking. The female usually has a 

 sharp ovipositor, which in many cases is used simply as a 

 sting. Development indirect. 



General Characteristics of Insects. i. Insects have a 

 segmented external skeleton, i.e. consisting of a series of 

 rings. 2. These rings are grouped in three sets, head, 

 thorax, and abdomen. The head bears one pair of an- 

 tennae. The thorax bears three pairs of legs and usually 

 two pairs of wings. The abdomen does not usually have 

 jointed appendages. 3. Insects have air tubes, branching 

 through the thorax and abdomen, by which they breathe. 



Harm done by Insects. i. They destroy crops, and the 

 damage to our field and garden produce is almost beyond 

 computation. 2. They convey disease both by getting on 

 diseased matter and conveying it to our food, and also by 

 introducing disease germs in biting (mosquito). 3. They 

 injure stock (flies, mosquitoes, botflies, etc.). 4. They 

 injure buildings (ants and white ants). 5. They are often 

 annoying, when not injurious, to man. 



^ Good done by Insects. They benefit us (i) by making 

 silk; (2) by making honey; (3) by furnishing material 

 for making ink (galls); (4) furnish dyestuff (cochineal); 

 (5) they are used in medicine (blister beetles); (6) their use 



