vii DEFENCES OF INSECTS 265 



cover of the appearance of which the weak and 

 decaying mimicking form shelters itself. As might 

 be expected from their usefulness, corresponding 

 imitations exist in other groups of insects. They 

 occur particularly among the Coleoptera, but these 

 are seldom so prominent, so easily recognised, or so 

 interesting, nor have they been subjected to the same 

 full investigation as the beautiful instances in Lepidop- 

 tcra. We will therefore pass on to consider those 

 cases where the mimicry occurs between species so 

 widely separated from each other as to appertain to 

 distinct orders. 



Sometimes the Lepidoptera lose the external 

 appearance of their order.* In two families of 

 British day-flying moths, the Sesiidse and ^Egeriidae, 

 their wing scales have almost disappeared and the 

 wings have become transparent, while the body is 

 usually straight and narrow, and the colour has been 

 modified so as to produce a more or less complete 

 resemblance to some stinging Hymenoptera. One of 

 the Bee Hawk moths, Sesia bombyliformis, a specific* 

 name recognising the similarity, suggests the appear- 

 ance of the male of the common Humble Bee, 

 B. hortorum. The mimicry of the Hornet Clear- 

 wing, Sphecia apiformis, is far more perfect, and 

 better calculated to delude the enemy. This insect 

 is one of the largest of these moths, and is a striking 

 imitation of a hornet or good-sized wasp. The 

 smaller Currant Clear-wing (Trochilium tipuliforme)^ 

 known for the depredations of its caterpillars on the 

 shoots of currant bushes, resembles a small black 

 wasp abundant in gardens at the same season. 



