166 



KNOWLEDGE 



[September 1, 1892. 



Fig. 7. — Larva of 

 Meloe, much mag- 

 nified. (After 

 Newport. 



vegetarians, feeding upon flowers, especially the two just 

 mentioned, it might be imagined that the young larvfe 

 possessed similar tastes, and had climbed into the flowers 

 to satisfy them. But such an idea would 

 be altogether erroneous, for in their 

 present condition they are not vegetarians 

 at all ; their true diet consists of bees' 

 eggs, and therefore they can make no 

 further progress with their development 

 until they have reached the inside of a 

 bee's cell. Hence ona would have thought 

 that, active and enterprising as they are, 

 they would have marched straight off 

 in search of bees' burrows, which could 

 not fail to be found somewhere near by ; 

 but this they show no intention of doing. 

 Their entry into their new pasture 

 grounds is to be made in a much more 

 romantic fashion, for they must wait till 

 theycan secure the services of some aerial 

 steed, on whose back they may ride in 

 triumph to their destined quarters. Here, 

 then, is the explanation of their- presence in the flowers, 

 for some chance bee alighting on them is to become the 

 wished-for Pegasus. Not that any bee will do — it must be 

 one of the Anthophonr described in our last paper, or else 

 an Andiimi ; should such an insect pay the flower a ^-isit, 

 the little parasite is ready to scramble on to its back while 

 it is busy rifling the flower. One can understand with 

 what a firm grip it would seize the bee's hairs, for it is a 

 matter of life and death, and should one chance be missed, 

 another may not occur for a long time. This, no doubt, 

 explains the very peculiar shape of the parasite's feet ; for, 

 in addition to the usual pair of claws at the end of each 

 foot, there is a central pad whicli looks like a third claw, 

 and gives the foot the exceptional appearance of a three- 

 fingered hand. These little insects are also sometimes 

 found on the bodies of flies, but whether this is due to 

 miscalculation on their part, or to intention, cannot be 

 stated, nor is it known what afterwards becomes of such 

 larvffi. There is, indeed, some doubt as to the exact course 

 followed by the Meloe. larva after it has gained the bee's 

 back, but as the transformations of an allied species called 

 Sitaris munilis, which occasionally occurs in this country, 

 have been fully worked out by M. Fabre, and as those of 

 the Meloe are probably almost identical with these, we will 

 now follow the fortunes of the Sitaris larva. 



The Sitiii-is is a brown beetle which is parasitic upon an 

 Anthophora. Unlike those of },leloe, its eggs are laid at the 

 entrance of the burrows of the bee. They are hatched in 

 September or October, but the young larvae, instead of at 

 once effecting an entrance into the cells of the bees, remain 

 where they are till the following April, taking no food all 

 this time. The larv;r of Meloe seem to be equally well 

 able to endure ]Drolonged fasting, a very needful thing in 

 their case, as they may have to wait long for the bee's 

 visit which is to give them their great opportunity in life. 

 The males of the Anthophora are the first to issue from 

 the burrows in spring, and as they pass out the young 

 parasites attach themselves to them. Soon, however, they 

 transfer themselves to the females, and thus secure the 

 means of entrance into the newly-made cells. When a cell 

 has been provisioned by the careful mother with a supply 

 of honey and pollen, an egg is laid and floats on the semi- 

 liquid mass. Now is the chance of the Situris larva ; as the 

 egg is laid, the parasite drops upon it, apparently unnoticed 

 by the bee, which proceeds to fasten up the cell. The 

 parasite now has everything its own way, though care is 

 needed, for if it were to fall oft" the egg it would perish in 



the sticky mass beneath. Sitting on its tiny raft therefore, 

 it nibbles a hole in the egg-shell and begins to devour the 

 contents ; so small a creature is it, that this egg lasts it 

 for a week's meals, and then it undergoes its first trans- 

 formation on the empty egg-shell. No fairy's wand ever 

 produced a more st irtling change than the simple process 

 of skin-changing now efl'ects ; the active, enterprising, six- 

 legged, slender larva becomes a fat, lethargic, almost legless 

 grub (Fig. 8 — 1), whose tastes are as much revolutionized 

 as its appearance. Animal matter not being now obtainable, 

 a vegetable diet must perforce be substituted for it, and the 

 grub succeeds to the inheritance of the young bee whose 

 birth it has prevented — viz.,thecell-fullof semi-liquid honey; 

 on the surface of this it floats, with its mouth buried in the 

 mass, so that it has but to lie still and eat, and no 

 exertions are necessary to enable it to take its fill. Its legs 

 are therefore reduced to mere stumps, and locomotion 



Fro 



Grub of Melon, slio\\-ing its tbree stages. 



becomes to it a lost art. It is so constructed that its 

 spiracles are situated high up on its back, and therefore 

 out of reach of the sticky sea in which it floats, and which, 

 if it came in contact with them, would inevitably clog them 

 up and suffocate the grub. When the honey is all consumed, 

 a further change takes place ; the grub contracts, detaching 

 itself from its skin, which darkens and hardens, and becomes 

 a barrel-shaped body (Fig. 8 — 2), within which the enclosed 

 larva proceeds stiU further with its development. After a 

 while another moult occurs, and again the form is changed, 

 the insect appearing as a fat six-legged grub, with spiracles 

 in the natural position (Fig. 8 — 3). After this it changes 

 into an ordinary chrysalis similar to that of other beetles, 

 and finally, after all these wonderful adventures, in the 

 month of August the perfect beetle appears, and we are 

 again brought back to the starting-point of the marvellous 

 cycle of transformations. The life of an oil-beetle is very 

 similar to this, though perhaps a trifle less complicated. 

 From facts such as these, and the instance is by no means 

 a solitary one. Sir -lohn Lubbock has been led to the con- 

 clusion that, while the form of the larva of any insect is 

 to some extent dependent upon the order to which it belongs, 

 yet it is also greatly influenced by the external condition's 

 to which it is exposed ; in other words, that there are often 

 changes through which an insect passes which are not to 

 be explained by reference to the form the insect will 

 ultimately assume, but are determined solely by the cir- 

 cumstances in which it then finds itself, and that therefore 

 we may find the usual form that belongs to the larv;D of 

 one order imitated in another, provided the circumstances 

 of the larval life are similar, although the perfect insects 

 produced will be totally unlike. 



There yet remains for consideration a species of para- 

 sitism which affects our wild bees far more intimately than 

 any we have yet passed in review, influencing not merely 

 their comfort and well-being, but even their very form. 

 The parasites in this case constitute an extraordinary 

 family of insects which are apparently not distantly related to 

 the Meloidic ; for in them we find the same transformation 

 from an active six-legged larva to a footless grub, com- 

 plicated, however, by the fact that the grubs are internal 

 parasites and live, not upon the bee's food, but upon the 



