144 



KNOWLEDGE. 



[August 1, 1892. 



so that abundant opportunities are afforded to parasitic 

 insects of various kinds to effect a surreptitious entrance. 

 Disguise therefore would, in such cases, serve no good 

 purpose, and accordingly we find that the parasites of the 

 solitary bees do not mimic their hosts, but are often as 

 unlike them as could well be imagined ; they seem, in fact, 

 in some cases to have gone to the other extreme of casting 

 caution to the winds, and boldly advertising themselves in 

 the brightest of colours. For obvious economic reasons the 

 diameter of the burrow is usually not much more than suf- 

 ficient to admit of the easy passage of the bees along it. 

 This, no doubt, has some effect in determining what insects 

 shall be parasitic upon any given species of bee, for it evi- 

 dently fixes a maximum limit of size for the invader, none 

 being able to gain entrance whose dimensions are too 

 portly. Moreover, as in the majority of eases the stranger 

 will be reared either upon the food stored up for the young 

 bee or upon the young bee itself, we may expect that for 

 this reason also the size of the parasite will not exceed that 

 of its host. 



Our British insect fauna would yield many illustrations 

 of the above general principles, for there is probably no 

 species of industrious bee that is not subject to parasitism 

 of some sort or other. A few of the most remarkable of 

 these may be given, and, as in our former paper, we will 

 first consider the parasitism of bee upon bee. There is 

 an insect commonly found burrowing into banks which is 

 no doubt often mistaken for a humble bee. The female is a 

 stout-bodied, densely hairy, black creature, with blunt 

 round body, and thick reddish brushes on its hind legs ; 

 the male is altogether different, being yellowish brown, 

 with long shaggy tufts of hairs on its feet. Notwithstanding 

 that it has somewhat the appearance of a l^amhus, it is not 

 a social insect, though it is gregarious ; by which is meant, 

 that the species does not consist of large numbers of 

 individuals of three sexes inhabiting the same nest, but of 

 pairs of individuals of two sexes not living in the same 

 nest, but each female constructing a separate burrow for her 

 own young, though in close proximity to those of her 

 neighbours. They may be distinguished from the social 

 humble bees by the structure of the hind legs, on which no 

 " corbicula " is found, such as a Bomhus would have. 

 This bee is called Antlwphura pilipcs, and it is one of the 

 earliest to appear in spring time. It builds, or rather 

 excavates, in steep bare banks or other exposures of earth, 

 and will often take advantage of artificial accumulations of 

 this kind. Thus I once saw a large colony which had 

 formed their burrows in the walls of a thatched shed built 

 up of turf, clods of earth, and dried mud ; the bees were 

 flying in swarms round the building, busily engaged in 

 constructing their cells or provisioning their nests. 



This insect has associated with it an extremely handsome 

 parasite called ilch'cta annntn, which is a bee of an 

 intensely black colour, with ash-coloured hairs on the head 

 and thorax, and beautiful snow-white tufts adorning in 

 elegant contrast the sides of its otherwise jet black abdomen. 

 It has a pointed body which is nearly bare, save for the 

 snowy patches, and, of course, its legs do not carry brushes 

 for the conveyance of pollen ; in fact, milike most bees, 

 parasitic or otherwise, it ajipears to visit flowers very 

 seldom. From this description it will be seen that the 

 parasite is quite unlike its host, both in shape and adorn- 

 ment. There is great difficulty in accurately determining 

 the dstails of the life-history of many of these bees, as will 

 be evident from the fact that their nurseries are situated 

 several inches below ground at the ends of narrow and 

 dark passages, and that all the incidents of their domestic 

 history are transacted in these retreats, remote from the 

 curious eye of man ; but it is pretty certain that in these 



cases of the association of bee with bee, the egg of the 

 parasite is laid upon the store of food provided by the 

 industrious bee, and the larva of the parasite, instead of 

 that of the host, is nourished upon this store. Thus, from 

 the habit of laying their eggs in other bees' nests, and 

 leaving their young to be fed with materials furnished 

 by a foster parent, these and other bees with similar habits 

 are often called cuckoo-bees. It is a curious fact that 

 there is another species of Anthophora very closely allied to 

 the above insect, so closely indeed, that it needs a keen 

 scrutiny to detect the points of difference, and that this 

 too has a Mclecta parasitic upon it, which agam is specifi- 

 cally distinct from the other, though equally closely allied. 

 Hence it would appear that the association of these bees is 

 of long standing, and that whatever causes have produced 

 the differences between the two hosts, have in like manner 

 affected the parasites, though not quite to the same 

 extent. 



We have a large genus of elegant bees with bare legs 

 and bodies, which latter are very prettily variegated with 

 bands of brilliant yellow, reddish, and black ; hence they 

 are often called wasp bees. They are, however, true bees, 

 and are not vindictive like the wasps, for, though the 

 females are possessed of stings, they cannot do much 

 dama.ge with them. They have the additional advantage 

 of exhaling a fragrant odom'. The genus is called Xmnacld, 

 the name being given in consequence of their roving 

 habits ; for they appear to be entirely parasitic, being in 

 fact structurally mcapacitated for the collection of pollen. 

 Very little is definitely known of their economy, but 

 it would appear that their eggs are laid in the nests of 

 sober-coloured industrious bees, especially those of the 

 large genus Andrena, and it has been thought that 

 they are laid before those of the rightful owner, so 

 that, when the latter finds the store of food she has 

 accumulated appropriated by a stranger, she deserts 

 the cell, and forms another, leaving the intruder in 

 undisputed possession. Sometimes two eggs are provided 

 for a single cell, in which case one or both of the resulting 

 bees is often smaller than usual. These parasitic bees 

 must, in fact, often be driven to considerable straits in their 

 endeavours to make a fair provision for their progeny, 

 being so entirely dependent upon charity ; visits to many 

 a burrow may be necessary before a cell can be found with 

 a sufficient store of pollen already accumulated, and after all 

 the egg may have to be laid in an insufficiently provisioned 

 cell, so that, in return for their shiftless habits, they have 

 to run the risk of great variations in size, some being much 

 dwarfed by a deficiency of food. As a compensation for 

 these risks, they are spared an immense amount of labour, 

 especially in the excavation of burrows and the collection 

 of pollen. The hollowing out of a main tunnel to the 

 depth of six inches or a foot, with short branch tunnels 

 opening out of it, and all by the successive snipping off' of 

 fragments of earth with the jaws, and their conveyance 

 outside, represents for a small insect a great deal of hard 

 labour. And then the search for suitable wild flowers, 

 growing within reasonable distance of the nest, and the 

 collection from them of pollen to be worked up successively 

 into pellets, one for each cell, involves a great many 

 journeys and a considerable expenditure of time, which 

 must often tax the energies of the industrious bees to the 

 utmost. From all these toils the Xomaihr are exempt, 

 unless indeed the closing up of the cells after they have 

 laid their eggs devolves upon them as some have supposed ; 

 notwithstanding the risks therefore, they must, on the 

 whole, find the practice of parasitism pay, or they would 

 have become extinct ere this. 



The Nomiidie are not interfered with by their hosts, 



