236 Annual Report for 1907 of the Zoologist. 
moth, whether becaiise it is less common or because it is 
regarded as inevitable, it would be interesting to know. An 
account of it appeared in the Zoologist’s report of 1903. 
It sometimes happens that alarm is caused by the presence 
of large numbers of insects of unfamiliar appearance in stables 
or cow sheds. Such a case was reported from Truro in July, 
and as other Members may meet with a similar experience it 
may be alluded to here. The creatures were well described as 
grubs “ of a dull grey colour, walking al)out like caterpillars, 
but with a long tail. They appear to hang themselves by the 
tail in any suitable crevice in walls or doors, and are very 
abundant in all the cattle houses here.” 
The creatures in question were the grubs of the “ drone fly,” 
Eristalis tenax, an insect very closely resembling the honey- 
bee, and perfectly harmless. Their presence in such localities 
is accounted for by the fact that the grul)S live in liquid filth, 
and their long tails (which cause them to be known as “rat- 
tailed larvae ”) bear the breathing orifice, which can be kept 
above the surface while their bodies are immersed in the 
manure in which they breed. When climbing the walls they 
were fully fed and ready to turn to chrysalids. Their bee-like 
appearance probably gave rise to the very ancient belief that 
honey bees could originate from “ carcasses ” or other decaying 
matter. They do no harm in the cow sheds, and in green- 
houses, where they often appear in the autumn, it has often 
been asserted that they are largely instrumental in cross- 
fertilising certain plants — especially chrysanthemums. 
Nursery Garden Pests. 
Rather a large number of the pests inquired about during 
the past year were injurious to the garden rather than to the 
farm, though, except where flowering plants are concerned, 
the distinction is perhaps unimportant. The increasing fre- 
quency of a not very familiar rose pest deserves mention, and 
there are other injurious insects to which the very mixed 
produce of gardens renders them especially liable. 
Many pests attack the rose, and some, such as the aphis, 
the yellow saw-fly, and the green rose-beetle {Cetonia 
aurata), are familiar to most growers. The black saw-fly 
{Blennocampa pusilla) is less well known, but it has occurred 
rather frequently of late on cultivated roses. The attack may 
be recognised at once by its effect on the bushes, for the young 
caterpillars, by their feeding, cause the leaves to roll up in a 
cylindrical fashion, giving the plants quite a characteristic 
appearance. 
The saw-fly is a very small insect, only one-seventh of an 
inch long, with a span of about one-third of an inch across the 
