128 



KNOWLEDGE. 



[July 1, 1898. 



collection be given, it will suffice to show how greatly 

 these marble galls are appreciated by various kinds of 

 insects. The collection in question was made in the 

 winter of 187S-0 by Mr. W. P. Weston, and it included 

 six species of small moths, all belonging to the group 

 Toitritt's, the caterpillars of some of which we have 

 lately had under examination, seven different kinds of 

 beetles, and no less than thu-ty species of Hymeuoptera, 

 including sawtiies, gall flies, ichneumon flies, chalcids, 

 ruby-tails, mason wasps, and other burrowing Hymen- 

 optera, and finally bees. We may briefly consider 

 what was the connection between these various insects 

 and the galls. 



In many cases, no doubt, it was simply a matter of 

 hibernation. The damaged galls especially would form 

 excellent retreats for all sorts of insects, provided their 

 size were not an obstacle. 

 This would certainly explain 

 the presence of the beetles 

 at least. Then, again, the 

 galls in their younger con- 

 dition, when they are soft 

 and j uicy , would no doubt be 

 as attractive as an article of 

 diet to some other plant- 

 eating larvie as they are to 

 those of the gall-flies them- 

 selves, and such larvre 

 would therefore frequent 

 them for food. This was 

 certainly the case with at 

 least one of the moths, 

 which is regularly an in- 

 liabitant and devourer of 

 galls. Other caterpillars, 

 again, might use the 

 damaged gall as a retreat 

 during pupahood. The 

 presence of the saw-flies 

 would probably be explained 

 in this way. The ichneu- 

 mons were of course para- 

 sitic on the moths and saw- 

 flies, the chalcids un the 

 gall-flies. The burrowing 

 Hymenoptera, many of 

 which tunnel in wood, had 

 apparently selected thegalls 

 for their burrows, and they, 

 again, would bring their 

 parasites with them, which 

 would account for the pres- 

 ence of the splendid little 

 ruby-tail, whose habits are 

 in accordance with this 

 supposition. The bees were 

 a very minute species belonging to a group which make 

 their nests in all sorts of localities, such as the hollow 

 stems of plants like brambles or docks, the deserted 

 burrows of other insects, holes in stones and cracks in 

 walls, and, e\-idently, we may add in galls also. Thus we 

 have seen that when a Cynips h'oUaii makes a puncture 

 in an oak bud and lays an egg there, she is performing an 

 act which may have consequences of the most varied 

 character, and may benefit not only her own offspring but 

 hosts of other creatures as well. And what is true of this 

 particular kind of gall applies no doubt, with modifications, 

 to other species in hke manner. 



[Tu be continued.) 



T 



Tree Creejiers on an Oalc Tree cunt 



THE TREE CREEPER. 



By H.\KRV F. WiTHERBY. 



HE tree creeper {Certhia faiiiili<iriK) is the smallest 

 of our true climbing birds, measuring only five 

 inches in length. 



The species is distributed generally over 

 England, and although migratory in other 

 countries, it remains with us all the year round. 



On account of its unpretending habits and its general 

 colouring, which assimilates itself to the natural haunts of 

 the bird, the creeper is not often seen, and consequently it 

 is usually considered to be more rare than it really is. 

 The tree creeper is very sombre in colour. The back and 

 head are dark brown streaked with greyish brown, the 

 wings are the same in ground colour, but have several 



bars of greyish white run- 

 ning across them. The 

 tail is reddish brown, and 

 the centre of each feather 

 is of a dull white. The 

 chin, throat, and belly are 

 of a silvery white, often 

 soiled by the bird's contact 

 with the tree. 



The favourite rosort3 of 

 this bird are wooded dis- 

 tricts and the larger kinds 

 of trees. It is especially 

 fond of localities in which 

 there are a number of trees 

 grouped together, such as 

 an avenue of trees, so that 

 it can move from one to 

 another without interrup- 

 tion. It is a very solitary 

 bird, and is either seen 

 alone or in pairs, but never 

 in large numbers. 



The manner of its climb- 

 ing is diflereut from that of 

 all other birds of its family. 

 The creeper almost invari- 

 ably commences to climb at 

 the bottom or very near to 

 the bottom of the tree, and 

 it then proceeds upwards in 

 a spiral direction, winding 

 its way round and round 

 the trunk, searching for 

 insects in every possible 

 crevice. Arrived at the top 

 it seldom flies to a different 

 part of the same tree, but 

 goes to the base of another 

 and repeats the same opera- 

 is an exceedingly active little bird, and when 



tion. It 



seen is usually thus employed, seldom being at rest in the 



daytime. 



The creeper climbs by making a number of quick move- 

 ments — so rapid are they that if the bird is not carefully 

 watched it seems to be gliding evenly up the trunk; hence, 

 no doubt, its name, which is apparently a misnomer, for 

 it is really a tree climber. 



It climbs in its neat way by means of its claws and tail. 

 The claws are long and curved, three pointing forwards 

 and one backwards, and with these the bird obtains a 

 secure hold on the tree. The feathers of the tail are stiff 

 and pointed, and the tail itself curving downwards when 



