8053 Insects, 



characters must be required to separate them from each other. The 

 characters I would rely upon for specific distinction may readily be 

 found in the general shape of the head and the prominence of the eyes, 

 the outline of the thorax, the length of the elytra, and the more or less 

 obtusely pointed abdomen ; the comparative length of the legs and 

 antennae should also be taken into consideration, although the species 

 do not differ so much in this respect. In colour they resemble each 

 other very closely, and this is often so much affected by the manner in 

 which they are killed that it cannot be considered of much importance 

 as a mark of difference. Of these characters the length and shape of 

 the abdomen is one of the most useful, and it is of all the most difficult 

 to preserve. In specimens which have been killed in the usual manner 

 by immersion in hot water the abdomen generally contracts so much 

 in drying that its original form is altogether lost. Instead of the hot 

 water system I would recommend equal proportions of spirits of wine 

 and water. In this they may remain for some days without injury, but 

 when once taken out of the bottle they must not be left for many 

 minutes before they are gummed on card, and even then some will 

 still shrink up. A better plan than this, under certain conditions, is 

 to use benzine collas instead of spirits of wine and water, but it requires 

 more care, and should only be used when they can be set soon after 

 they have been killed ; if allowed to remain in the liquid for many 

 hours the limbs become rigid, and it is almost impossible to set them 

 properly. 



In searching for Ptinellaj the tree on which they are found will often 

 assist the collector in distinguishing the species. It cannot always be 

 relied upon, as the same species may occur on trees of various kinds, 

 but nevertheless it so often happens that trees in different localities, 

 although of the self same sort, are inhabited by different species of 

 Ptinellge, that all should be carefully examined ; of course the chance 

 of finding a fresh Plinella is much increased when the tree is of a dif- 

 ferent species. 



There is yet another circumstance respecting the affinity of the 

 winged and apterous Ptinellae which must not be overlooked, and which 

 can be observed only in the act of collecting ; it is this, that although 

 winged examples are comparatively very rare we have invariably found 

 them in company with that particular apterous species to which they 

 bear the strongest resemblance. 



In reviewing the nomenclature of the Ptiuellse I particularly wish to 

 direct attention to this point, that all the British specimens of the genus 

 now bearing the name of P. denticoUis belong to the P. aptera of Guerin, 



