18 Mr. F. Muir and Dr. D. Sliarp on 



covering would doubtless suffer greatly from drought, or 

 downpours, or great changes of tempemture. We may 

 feel sure therefore that the ootheca of this insect, surround- 

 ing as it does the eggs with a complete periphery of large 

 air-cells, is very valuable, and it may aid the survival of 

 the young, even if the structure should be covered with 

 sand. 



The ootheca does not offer protection from parasites. 

 ]\Ir. Muir has found that the eggs of A. inmcticosta are 

 very extensively parasitized. In the case of one species of 

 Chalcid he has observed the oviposition ; the little parasite 

 sits on the back of the beetle and flies down and oviposits 

 in an egg whenever it feels inclined. The construction of 

 an ootheca containing about 80 eggs occupies about 20 

 minutes, so that this paiasite has plenty of time for its 

 operations, and the Cassid would clearly be more efficiently 

 protected against its attacks if the ootheca were dispensed 

 with and the eggs deposited rapidly and covered with a 

 coat of membranes similar to the shell layer of the Basipia 

 ootheca. The Chalcid parasites that emerge from these 

 Cassid oothecas are very numerous, Mr. Muir having 

 already discovered several species. They do not, however, 

 seriously affect the perpetuation of the species, as Mr. 

 Muir considers A. punciicosta to be a common insect from 

 Durban to Zanzibar; and it probably extends farther, as 

 he thinks he has seen it at Aden. 



The variety of the oothecas in these seven or eight 

 species of CassididcV is very remarkable. The contrast 

 between the small irregular structure of Cassida unimacula 

 and the large and complex edifice produced by A. puncticosta 

 is very striking. 



Although the puncticosta ootheca is a really admirable 

 production, there is no reason to suppose that any skill is 

 exhibited in its production. The operation seems to be 

 more comparable with the actions of a machine. The 

 factors that contribute to its superiority (if we may use 

 such a term) are of the simplest character : viz. the large 

 size of the insect, the order in which the eggs are depo- 

 sited, and their large number, the completely stationary 

 position of the insect, the great width of the orifice of the 

 abdomen from which the colleterial fluid is exuded, and, 

 above all, the remarkable qualities and great abundance of 

 the colleterial fluid. It is from the combination of these 

 characters that the perfection of the structure results. The 



