278 BRITISH HYMENOPTEliA. 



certain species of Andrena; but there are others, as Nomada ruficornis, 

 succincta, alternate/, and Lathbwriana, which infest the nests of several species 

 of Andrena indiscriminately; the species are A. tibialis, Trimmerana, Afzeliella, 

 and fulva; but the following I have never observed, except connected as 

 follows: — Nomada lateralis and A. longipes, N. baccata and A. argentata, N. 

 borealis and A. Clarkella, N Germanica and. A.fulvescens, and, lastly, N. 

 sexfasciata and Eweera longicornis. Much further investigation is still neces- 

 sary before we can arrive at a knowledge of the real nature of the connexion 

 which exists between the bees and their parasites. It has been supposed 

 that the parasitic larva is hatched sooner than that of the rightful owner of 

 the nest, and that it consequently consumes the food, and leaves the larva 

 of the bee to perish; but to this I do not assent: it appears so contrary to 

 all natural laws, that I cannot think it even probable: nature I have never 

 observed to be thus wasteful of animal life — such a proceeding is unnecessary, 

 and therefore unlikely: where a destruction of animal life is observed, it 

 can usually be traced to some reasonable cause, as the destruction of the 

 larvae of certain Lepidoptera, being a check upon their superabundance: a 

 parallel to this does not appear to me to exist in the case of the bees: I am 

 more inclined to believe, that when the parasite has deposited her egg upon 

 the store of pollen, the industrious bee at once deserts it, and proceeds to 

 construct a fresh burrow; and that the parasites which may be observed 

 constantly entering different burrows, do so in order that they may find the 

 requisite quantity of food, which will usually be much less than that required 

 for the industrious bee; having found which, they deposit their egg, and the 

 nest is then possibly deserted by its legitimate owner. 



The Andrenidce are also subject to the attacks of other enemies, if so they 

 can be called; we have seen that in the first place their food is attacked by 

 Nomada, we are now to find their larva? attacked by insects belonging to 

 the Order Coleoptera; these belong to the genus Stylops, which several 

 distinguished entomologists of the present day agree in placing amongst the 

 Heteromerous parasitic beetles. These insects were placed in a new order 

 by Mr. Kirby, named Strepsiptera, and as such they are still regarded by 

 many entomologists; we have at present only to do with them as enemies to 

 the bees, and briefly to narrate the manner in which the latter are attacked 

 by them. These insects are diminutive in size, the largest known species 

 not exceeding a quarter of an inch in length; we are now speaking of the 

 winged males; the females are apterous grub-like insects, which never leave 

 the bodies of the bees. If the abdomens of a number of Andrenidce be 

 examined, it is most probable that the female of Stylops will be found; her 

 presence is known by the protrusion of her head and a portion of the thorax 

 between the abdominal segments on their superior surface, resembling the 

 point of a small bud of a brown colour, or rather a flattened scale. I have 

 several times bred the larvae of Stylops in the following manner: — On finding 

 a bee infested as described, place her in a box five or six inches square, 

 cover it with gauze, and supply the bee with fresh flowers such as the 

 Andrenidce frequent; examine the bee every day, and it is most likely that 

 in eight or ten days she will appear as if her abdomen were covered with 



