A. COTTAir OBSEEVATION OP INSECTS. 51 



The Entomology of "Watford and its neighbourhood has never, 

 that I am aware of, been worked, or if it has, there is no record 

 of our fauna, so that there is an excellent field for work here ; 

 and I would ask the lady members of our Society to help us in 

 this matter, for so many insects are entirely day-fliers, and can 

 only be observed or taken in the mid-day sunshine, when com- 

 paratively few gentlemen have leisure or opportunity to be out 

 in the country, that, with the butterflies especially, we shall have 

 to trust very much to our lady friends to look out for their 

 appearance. 



I append the remarks of Mr. McLachlan, given in the Meteoro- 

 logical Society's * Instructions. ' 



The time of first appearance of any particular species sliould be carefully noted, 

 as also the time when it becomes common. This is especially necessary -with the 

 two white butterflies, for, as certain larvae of these often enter houses and other 

 buildings in order to undergo their transformations, it foUows that these will 

 necessarily be developed before the main body of individixals that pass through 

 their transformations out of doors. 



Notes on the species here follow : — '^'^ 



72. The appearance of the cock-chafer may be taken as an indication of the 

 near approach of summer. 



73. The fern-chafer is a beetle much like the cock-chafer in appearance, but 

 very much smaller. It flies in swarms in the evening round any object (trees, 

 the observer, etc.), and indicates that summer has fairly set in. 



74. The honey-bee need not be observed after the end of March in spring, or 

 before the end of October in autumn. 



75. 76. The Uvo white cabbage-butterflies need only be noticed in their vernal 

 broods. F. Rapce always appears before P. Brassicce, and care must be taken to 

 avoid mistaking for the latter, hybernated females of Gonopteryx Rhatnni (the 

 brimstone butterfly) , which appear in fine sunny weather from the earliest advent 

 of spring or the end of winter. [Records of the first appearance of this butterfly 

 will, however, be useful.] 



77. The meadow-brown butterfly may be taken as indicating summer. 



78. St. Mark's fly is a large intensely black hairy dipterous insect with rather 

 long legs, appearing generally about St. Mark's Day (April 2oth), and lasting for 

 a very short time. 



79. The winter-gnat dances in the air (singly or in little swarms) throughout 

 the winter, excepting during the hardest frosts. A continuous record of its ap- 

 pearance shoxild be kept from Christmas to the end of March. 



Occasional appearances in unusual numbers. — It is well known that certain 

 insects appear occasionally in enormous numbers, and then are comparatively rare, 

 or disappear altogether, for a series of years. Vanessa Cardui (the painted lady 

 butterfly), Colias Edusa and Sijale (the clouded-yellow butterflies), Sphinx Con- 

 volvuli (the convolvulus hawk-moth), are familiar examples. Such exceptional 

 occurrences should be carefully noticed. Meteorologists may thus possibly throw 

 light upon phenomena that have never been satisfactorily accounted for by 

 natiiralists. 



* The numbers prefixed to these notes refer to the list of the species, which 

 will be foimd at page 37. 



