56 THE CAUSES WHICH PROPAGATE 



smell;, as the Blue-bottle Fly, who not unfrequently oviposites 

 on certain hothouse blossoms redolent of carrion, her proper 

 food and nidus. Many moths, according to Dr. Knaggs, will 

 not lay until presented with some strong nostrum ; but other 

 sorts seem to be influenced by sight, as Trichoptera, Avhom I 

 have known to attach their ovse to a fly's wing, evidently mis- 

 taking it for the reflection of a glassy brook. Nest and cocoon 

 making, with insects, is evidently a provision against the fluc- 

 tuations of season, and especially the periodical visitations of 

 winter's cold and dearth. No perfect insect, however, spins 

 as caterpillars previous to metamorphosis, but both natural 

 endowment and economy are employed. Provident for the 

 larvae, some Orthoptera, as cockroaches and MantMa, lay their 

 eggs in a case, like the skate and dog-fish. Some Lepidoptera, 

 as the moths of the Liparidse, possess a dense woody tuft of 

 coloured hair around the anus, which they snip with pincers to 

 cover and protect them. European kinds, either like the Brown 

 and Gold Tail Moths oviposite on leaves in summer, or, like the 

 Gipsy Moth, place their eggs on tree-trunks at autumn. Other 

 moths glue their eggs together in the form of a necklace 

 around twigs, and Gnats thus construct a floating raft on the 

 surface of the water. The female of the Coccidse, a tribe in- 

 cluding the cochineal insects, excludes a cottony down with her 

 eggs, as the American blight, or simply dies Avith the ovse in 

 her body, which then forms a shelly cover. 



To insert their eggs, Cicadae and Saw-flies cut grooves into 

 twigs with the sensations of their ovipositors ; and other tribes 

 that have this external oviduct similarly indurated, as the Gall- 

 flies and Leaf-crickets, use it more or less as a drill. Fosso- 

 vial and wild bees, with some lamellicorn beetles, on the contrary, 

 employ their mandibles or forelegs to excavate holes in friable 

 earth or wood, and form a simple or compound nest. As 

 regards providing for the young, bees are not equally proficient, 

 and it would almost seem as if we could trace various degrees 

 of intelligence. Some, as the Phytophaga, resemble the moth 

 kind in their transformations; others, as the Biophaga, which 

 includes the ichneumon flies, deposit their eggs in certain 

 insects, in whose bodies the young undergo their transforma- 

 tions j and others instead maim these insects, and drag them 



