80 MICHIGAN ACADEMY OF SCIENCE. 



scale that gives the name to the family. Indeed the legs are shed after 

 the first molt and wandering then becomes impossible. This shield or 

 scale is usually papery, sometimes haying a waxy or horny appearance. 

 It entirely covers the insect under it but remains at all times unattached. 

 The two skins that are cast by the female are incorporated with the 

 growing scale, and the first skin shed by the male is likewise utilized. 

 The second skin is shed by the male when the pupal stage is reached 

 and no further growth in the scale takes place after that time, so this 

 skin remains separate and never is iucorj^rated with the scale. Thus 

 we find in the skin of Hie female, two cast-skins and in that of the male 

 a single one, a feature of great taxonomic value. A short time after the 

 second molt, the male emerges as a delicate winged adult. Mating 

 occurs almost immediately and the male dies. 



The eggs are laid by the female under the scale, the body of the female 

 shrinking away to make room for them as they are laid. In some 

 cases, as stated, the young are born alive, the reproduction being 

 ovo-viviparous. The migration of these insects to new places, has to 

 take place just after they emerge from the egg and before the scale- 

 covering is formed. Before the first molt they are provided with legs 

 and these minute lice, so small as to be almost invisible to the unaided 

 eye, in running about to find suitable places for feeding, must crawl onto 

 the bodies of other insects and the feet of birds to be by them carried 

 to new fields of labor. Of course only a small proportion of the lice 

 carried off in this way ever alight on the proper food-plant, and if they 

 do, both sexes must be deposited at the same place or near each other, 

 else they will be unable to reproduce. Happily these conditions help to 

 restrict the spread of these creatures to any great distance except 

 in the case of species that are parthenogenetic. Unfortunately par- 

 thenogenesis exists among many species of the Coccidie and in some 

 species that have been under observation for a long time and which 

 have been repeatedly bred, the male has never been discovered. For 

 instance the males of some species of Lecanium are not yet known 

 though the females have been, the object of experimentation for years 

 and has been bred many times. Orthezia insi<jnis was not observed to 

 produce males in the United States up to a short time since, but they 

 are occasionally produced in England. I bred the species through 

 three generations and never found a male, though I had the species 

 under observation for the space of three years as well. The effects of 

 two closely allied scales on their respective host x^h^mts may be very 

 different indeed. Thus Aspidiofiis: (dici/Jks, a common scale of the orchard 

 and forest, will live a long time on a tree and never seem to cause it any 

 injury or become troublesome, but the Euroj)ean fruit-scale .1. ot^trcw- 

 forntis ov the San Jose scal(\ .4. pernlciosiis, will immediately show their 

 effects, causing the tree to die after a few years. Some scales cause a 

 stoy)pnge of gi'owth in ihe region affected, some discolor the inner bark, 

 staining it a beautiful purple color, some live for years in the same 

 place and do no apparent harm, and some become dangerous only 

 occasionally. It is sujij^osed that the damage is largely due to a fluid 

 injected into the baric for llie purjjose of iuci-easing the fiow of sap to 

 the place infested, just as the poison of a mos(]uito bite is supposed 

 by some to produce an increased flow of blood to the sjjot bitten. 



