Identifying Bed Bugs. When bed bugs bite - and even when one bites multiple times - it's common not to notice the area for a few days. Their saliva has anesthetic properties which promote blood flow at the site. Along with swelling and/or a red rash, it is common to find itchy red welts that can be small, flat or raised.
Barn swallow bugs resemble bed bugs as well. Although barn swallow bugs feed primarily on cliff swallows and live in swallow nests, they have been known to enter human dwellings when bird migration occurs. It is important to accurately identify bed bugs before beginning treatment of an infestation.
Bedbugs can be 1 to 7 millimeters long. They're flat, oval-shaped, and reddish-brown in color. They don't have wings, so they rely on animals or humans to carry them from one place to another.
The anatomy of a bed bug consists of an oval shaped body, a small broadly attached head, and compound eyes. Bed bugs are about the size of an apple seed (4-5 mm in length). They have segmented abdomens with tiny, colored hairs that give them a striped appearance. Their antennae are shorter than their legs and have four segments.
Photos of Bed Bugs - Actual Size Comparisons with Other Objects Adult bed bugs are typically about 5 mm or 1/4 inch long. Source: Centers for Disease Control (PD)
In exact size, Nymphs are in between the bed bug eggs (1 mm / 0.09 inches) to the size of an adult bed bug (4.5 mm / 0.18 inches). However, immature bed bugs are tiny in size (definitely) but will grow bigger as they suck more blood and molt.