Walker : The Ichneumon id j:. 



75 



A very natural question is — from what do the ichneumons take 

 their name ? I find an account, in an old natural history, of an 

 animal called the Egyptian ichneumon, which is asserted to dig up 

 the eggs of crocodiles and devour them. It is likewise said to attack 

 the young of that large-mouthed vertebrate, and massacre them mtis 

 ceremony. The book then proceeds to state that the animals were 

 fabulously supposed to deposit their young in the interior of the 

 crocodile, the parasites subsisting upon its flesh. I am puzzled to 

 imagine how the ichneumon could obtain entrance into the reptile's 

 interior ; possibly it kept a sharp look-out for some sleepy crocodile, 

 and when the latter opened its mouth to yawn, undertook an exploring 

 expedition down its throat, and commenced its maternal duties. How- 

 ever, be that as it may, such is the origin of the word " ichneumon," 

 as applied to insects, bestowed upon certain parasitical species by the 

 renowned Linnaeus. 



The Egyptian ichneumon is a native of Egypt, Barbary, and the 

 Cape of Good Hope, and is, from the tip of the nose to the end of the 

 tail, from twenty-four to forty-two inches in length, the tail being as 

 long as the rest of the body ; it is pale reddish-grey, the eyes are red, 

 and the nose long and slender. The tail is thick at the base, but tapers 

 towards the tip, which is tufted ; the legs are short. 



I will now take a typical ichneumon, Pimpla iitdigator, and give, as 

 briefly as possible, a summary of its external structure and appearance. 



The Head. — The antennae, which contain a varying number of 

 segments, according to species, are sometimes marked with a 

 broad, pale band, called the annulus. When walking, 

 parasitic Hymenoptem keep their antennse constantly vibrating. The 

 mandibles are thin and curved, the eyes generally very conspicuous. 

 In addition to the pair of compound visual organs, the Hijmenoptera 

 possess three other simple eyes, called ocelli, which are placed in a 

 triangular form on the top of the head, the tip, or vertex, pointing 

 towards the mouth. Some species of Lepidoptera are furnished with 

 a pail' of ocelli, which are generally overlooked, because of the " thick 

 covering of hair or scales." ^ They are possibly used for vertical sight. 



The thorax consists of three portions, the prothorax, the mesothorax, 

 and the metathorax. The prothorax bears on its under side the 

 anterior or first pair of legs, and also supports the head. The meso- 

 thorax supports the anterior wings and the second pair of legs. At 

 the base of each anterior wing is situate a concavo-convex plate of a 



2 Westwood's Introduction to the Classification of Insects, Vol. 2, 



