222 OUR HOUSEHOLD INSECTS 



flies, with antennae of ordinary size and of less extra- 

 ordinary shape. To the former division (Braehycera 

 short-horns) are referred the house flies and allied insects 

 discussed in the previous chapters, as well as hosts of 

 others less familiar ; while to the latter (Nemocera 

 thread-horns) belong a weak-limbed and fragile group, 

 the daddy-longlegs or crane-flies, together with the 

 numerous kinds of gnats, mosquitoes, midges, merry- 

 dancers, &c. (though not the equally, or even still more, 

 fragile May-flies or day-flies). It is with the section 

 Nemocera, therefore, viz., the thread-horned flies, that 

 we are now concerned. 



There is amongst the members of this group a strik- 

 ing variety, both as to habits and life-history. Some, 

 in their early stages, lead an active life in the water ; 

 others, of a more sluggish temperament, inhabit fungi 

 or rotten wood ; others, again, like the notorious Hes- 

 sian fly, are parasitic on plants, producing gall-like 

 excrescences within which they reside ; while yet others, 

 like the daddy-longlegs, whose larvae are the detested 

 "leather-jackets" of the gardener, live underground, 

 devouring roots of plants as well as vegetable refuse. 

 It might be expected that, with such diversity of habits, 

 there would be correspondingly great differences of form 

 in the adult insects. Such, however, can scarcely be said 

 to be the case, and thus many that are superficially 

 similar in the adult condition may have passed through 

 their preliminary stages under totally different circum- 

 stances. This fact, coupled with the fragile and easily 

 damaged structure, and consequent difficulty of preser- 

 vation, the obscure colours, and the comparatively un- 

 marked characters of the perfect insects, makes the nice 

 discrimination of species a very difficult task ; and it is 

 not surprising that the popular judgment has declined 



