642 INSECTS AT HOME. 



The life history of this insect is very remarkable. 



Fortunately for horses, the Horse Fly is anything but pro- 

 lific, producing its young in a mode which is, I believe, con- 

 fined to insects of this group. The mother Horse Fly never 

 lays more than one egg, but then that egg is a phenomenon. 

 In truth, it ought not to be called an egg, having no more 

 right to that title than the so-called ' ants' eggs ' which have 

 already bee" described. The reader may remember that the 

 eggs of certain Flies are hatched in the body of the parent, 

 so that they are deposited in the larval and not the egg state. 

 The Hippobosca goes a step further. The egg, as it appears to 

 be, is no egg at all, but the skin of the larva, within which 

 the pupa is formed, so that the young Hippobosca is already a 

 pupa when it enters the world. 



When first produced, the puparium (to use the scientific 

 term) is white ; but it soon darkens, and becomes quite hard 

 and tough. If it be opened carefully, within it may be found 

 the pupa, an odd-looking, crab-like being, with the legs tightly 

 folded over the body. When the time comes for the assump- 

 tion of the perfect state, it throws off the pupal skin, which it 

 leaves within the puparium, pushes off tlie end of the case in 

 which it had resided, and emerges as a perfect insect. 



The chief points in the external anatomy of this insect are 

 given on the same Woodcut. Fig. a represents one of the 

 antennce separated from the head. Fig. b is the part of the 

 mouth containing the diverging horns which have already been 

 mentioned, and Fig. c represents one of the fore-legs, with its 

 very powerful thigh, and its black, incurved claws. 



At Fig. 2 of the same Woodcut is seen the Swallow Fly 

 {Stenopteryx kirundinis), so called because it is found almost 

 exclusively on the swallow tribe. The generic name is formed 

 from two Greek words signifying ' narrow-winged,' and is very 

 appropriat-c, as may be seen by reference to the illustration. 



Mr. Kirby mentions that this Fly sometimes attacks human 

 beings : — ' One found its way into the bed of the Eev. E. 

 Sheppard, where it first, for several nights, sorely annoyed a 

 friend of his, and afterwards himself, without their suspecting 

 the culprit. After a close search, however, it was discovered, 

 in the form of this Fly, which, forsaking the nest of the 



