288 HYMENOPTERA 



of the Mutilla and the well known " Ichneumon " fly, 

 parasites of caterpillars. 



It may be remarked here that " parasite " hardly 

 seems the correct term for an Ichneumon larva, whose 

 activities necessarily result in the death of its host, which 

 is devoured as completely as an antelope is by a lion. 



The only difference is that at first the young Ichneumon 

 larva feeds only upon the juices of its prey, and the 

 essential tissues are not devoured until the larva is full 

 grown, when it has nothing to fear in the death of its 

 unwilling host. 



It does occasionally happen, however, if the dispro- 

 portion in size is great between the host and the parasite, 

 or if the number of parasites is very small, that the host 

 is not killed. I once reared an Arctiid moth and a single 

 parasitic Tachinid fly from the same caterpillar ! 



The habits of Bembecidae are, like those of other fossors, 

 of absorbing interest. As has been pointed out, these 

 feed their larvae on flies, ^ but they do not lay up one store 

 for good and all as do the Sphegidae and Pompilidae. 

 Perhaps the reason is that the flies, not being large-bodied, 

 fleshy insects, might dry up before the Bembex larva 

 had eaten them all. So the mother attends to her larva, 

 bringing to it freshly stung flies at frequent intervals. 



Since this necessitates constant work opening and 

 closing the burrow, it is dug in localities where the 

 soil is very loose and light, such as a sandy shore on the 

 lake, and I have found thriving colonies of Bembex in 

 such situations. 



The first that I met with was on a dazzlingly white 

 beach of fine sand on the south coast of Nsadzi Island, 

 in March 1911, when I found numbers of B. forcipata 

 flying about over the hot sand, and busily excavating 

 their burrows, and spent many hours watching them, 



^ Occasionally on other insects. I have watched one catch a " Skipper" 

 butterfly. See Proc. Ent. Soc, 1917, p. xli. 



