INTRODUCTORY REMARKS ON THE i\! YMARIDAE 



The Mymaridae are a family of excessively minute insects, 

 and anthorities are not agreed as to the position that it should 

 occupy in the great groups of Hymenoptera. Almost all the 

 known species are parasitic in the eggs of other insects. Those 

 species with which I am personally acquainted always emerge 

 singly from the egg that they have destroyed, hut others are 

 jired in some numhers from a single egg. Probably they at- 

 tack the eggs of almost all orders of insects, as I have bred them 

 from those of Lepidoptera, of Rhynchota, Homopterous and 

 Hemipterous, and also of Neuroptera, and they likewise destroy 

 tliose of Coleoptera. Some are recorded as having been bred 

 fiom scale-insects and plant-lice. Of the species hitherto describ- 

 ed, in comparatively few cases, are the hosts known, and it is safe 

 to say that all the species hitherto collected by Entomologists do 

 not amount to one in hundreds, that exist. Some of the larger 

 species may be obtained in numbers with the sweeping net by 

 anyone with good eyesight, and others are frequently seen in 

 plenty running on glass windows, especially those of hot-houses 

 in cold countries, as the English collectors observed three-quar- 

 ters of a century ago. The majority of the species that exist, 

 however, are not likely to be met with, except by breeding them, 

 for many are so minute, that except by chance thev cannot be 

 collected in the field. Some species do not exceed one-third of 

 a millimeter in length and others are said to be even smaller, 

 \\h\\e the pallid color of many of the minute species renders them 

 almost invisible to the naked eye. 



The long and tery slender wings, fringed with long hairs, are 

 one of the most striking characteristics of the family, and with 

 these delicate organs of ilight some even of the smallest s])ecics 

 can fly better than might have been expected. Many of them 

 have a frequent habit of rising slowly and vertically upwards on 

 the wing, and as they cannot withstand a moderately strong cur- 

 rent of air, this habit m,ust lead to a much quicker and wider dis- 

 tribution of the species than could ever be attained by their 

 own unaided powers of flight. The legs of most species are 



