D.—ZOOLOGY. 83 
emerge. It was finally discovered that the ‘cocoons’ are spheres of 
hardened froth evacuated by the Deilemera caterpillar and then attached 
with silk to the outside of its cocoon. The late Mr. G. F. Leigh, of 
Durban, was similarly deceived by an allied Hast African species and 
threw away three or four cocoons, thinking they had been parasitised. 
What interpretation can be suggested for adaptations such as these, 
except the selection and accumulation of small variations? And it is to 
be remembered that even in the mimetic butterfly of Plate I the associated 
instinct—the attitude assumed at rest—is an essential element in the 
resemblance, while in the construction of the false cocoons shown on 
Plate II, the instinctive actions are nearly everything. It is also to be 
remembered that these actions are prophetic, destined for the protection 
of a future pupal stage. This fact is so interesting and significant in its 
bearing on theories of evolution that I venture to bring before you two 
other especially striking examples, although, of course, prophetic activities 
are displayed by every caterpillar in spinning its cocoon or otherwise 
preparing for pupation. 
The larva of an African Tabanid fly (7. biguttatus) lives and becomes a 
pupa in mud which, in the dry season, is traversed by cracks so wide 
that they would often expose the insect in its most helpless stage. But 
Dr. Lamborn discovered that the maggot has prepared for this danger. 
It carves out a cylinder from the surrounding mud, making a line of 
weakness by means of a close spiral tunnel; then it enters just below the 
top of the cylinder and pupates in its centre. The pupa when mature 
bores its way through the hard mud covering and the fly emerges. Dr. 
Lamborn was led to his discovery by observing the tops of the cylinders, 
of about the size of a penny, often with the pupal shell protruding from the 
centre ; also by noticing that the cracks running in all directions stopped 
short when they reached the cylinders. I feel sure that you will agree 
with the words written by Prof. J. M. Baldwin when he read the account 
of this instinctive behaviour— As to the discovery of Lamborn, it seems 
_ complete—one of those rare cases of a single experience being sufficient to 
establish both a fact and a reason for the fact! It is beautiful.’ *4 
The other observation is also of especial interest, being an arresting 
example of the attainment of the same end by a different and unusual 
means. In leaving their cocoons some insects gnaw their way out, others 
make use of holes drilled by pupal spines, asin the last-mentioned Tabanid 
fly. The well-known ‘Puss-moth’ (Dicranura vinula) has been shown by 
O. H. Latter to soften the hard cocoon with a secretion of caustic potash. 
Many caterpillars in spinning their cocoons make special provision for 
easy emergence and difficult entrance, on the reversed principle of the 
lobster-pot, a beautiful example being our own ‘ Emperor Moth’ (Saturnia 
pavonia). Now these preparations are made in spinning the cocoon, but 
the caterpillar of an Indian moth allied to our ‘ Lappet Moth’ first nearly 
finishes its cocoon and then deliberately bites two slits in it. As Lt.-Col. 
F. P. Connor* has written : ‘ It was a striking fact to observe how the larva, 
24 Proc. Ent. Soc. Lond., vol. v., 1930, p. 14. Lamborn’s discovery is published 
in Proc. Roy. Soc., B., vol. 106, 1930, p. 83, pl. v. As this address was being written 
a letter arrived from my friend at Fort Johnston, Nyasaland, telling me that he has 
just bred another Tabanid fly, at present undetermined, from a mud cylinder like that 
of 7. biguttatus. 
2% Journ. Bombay Nat. Hist. Soc., vol. xxvi., 1919, p. 691. 
G2 
