110 PROTECTION OF WOODLANDS. 



taking place gradually and imperceptibly, so far as hard and fast 

 lines of difference are concerned. 



The Ova, or eggs, varying greatly in shape, size, and colour, are 

 sometimes laid singly, sometimes in larger or smaller groups or 

 nests on the most different portions of trees, and occasionally pro- 

 tected in some special way, as, for instance, with a covering of 

 hairy filaments; but in the case of parasitic insects, the eggs aiv 

 deposited on or in other species. The larva sometimes makes its 

 appearance from the egg in the course of a few weeks, sometimes 

 not until months afterwards ; for when ova are deposited during 

 autumn, they hibernate or pass the winter in that same condition 

 or stage of development. 



For the Larva, several appellations are made use of. Thus the 

 usually 16-footed larvae of butterflies and moths (only those of 

 the so-called Spanners Cfeometridce, have 10 feet, whilst a few 

 mining-larvae Tinddce have none are named caterpillars; the 

 18 or 22-footed larvae of saw-flies (Tenthredinidce), with a tail-like 

 extremity, are called tailed caterpillars ; the larvae of most 

 beetles, partly without feet, partly 6 -footed, are termed larvie 

 those, however, of the cockchafer species (MelolontJia), gn 

 whilst the feetless larvae of flies (Diptera), in which the complex 

 structure of the head is wanting, are known as maggots, 



During the larval stage several changes of skin take place. 

 When full grown, the larva becomes transformed into the pupa 

 or chrysalis, becoming either a free or sculpt chrysalis, with all 

 the different portions of the complete insect visibly apparent 

 externally, as in the case of beetles, or else a masked chrysalis 

 in the case of butterflies and moths (Lepidoptera), in which tin- 

 various segments and section* are not definitely apparent. The 

 pupa either lies naked and unprotected on the soil, under Bl- 

 under the bark, or in its fissures, &c., or else it is woven ini" a 

 cocoon, often of considerable toughness : in the case of the Dipt< 

 instead of any cocoon, a sort of bladder or shell is formed by the 

 last larval skin. 



The period of rest during the pupal stage varies greatly, extend- 

 ing from two to three weeks (as in the case of the very destruci 

 " Nun," Liparis monacha, for example) up to 6 or 8 months in the 

 case of hibernating species (e.g., Gastropacha pini), and occasionally 

 even for years (e.g., Melolontha)\ it is then terminated by tin- 

 appearance of the Imago or perfect Insect in its complete form 



