4. ANDRENA. 23 



pubescence, and readily observed from the brightness of its 

 colouring. 



To some extent I have observed that a constant connexion between 

 certain species exists, and I have never met with some species of 

 these parasites except in connexion with certain species of Andrena ■ 

 but there are others, as Nomada rvjicornis, succincta, alternata, 

 and lathburiana, which infest the nests of several species of Andrena 

 indiscriminately ; the species are A. tibialis, trimmerana, afzeli- 

 ella, 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. clarhella, N. germanica and 

 A. falvescens, and, lastly, N. sexfasciata and Eucera longicomis. 

 Much further investigation is still necessary 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 para- 

 sitic 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 ; bat 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 wastful of animal life ; such 

 a proceeding is unnecessary, and therefore unlikely : where a destruc- 

 tion of animal life is observed, it can usually be traced to some rea- 

 sonable 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 probably close up the cell ; the 

 nest is then deserted by its legitimate owner. 



The Andrenidae 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 Nomadce, we are now to find their larvae attacked 

 by insects belonging to the order Coleoptera ; these belong to the 

 genus Stylops, which several distinguished coleopterologists 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 some 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 Andrenidae be examined early in the season, 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 



