The Insects of Spring

Are flies buzzing around your lights and bonking against your windows?  One of the less pleasant signs of Spring and warming temperatures is that the insects that have been overwintering in the attic and wall voids of homes become active and often wander into the living space delighting cats and irritating homeowners.
Insect accidental invaders are bothersome, annoying and a nuisance, but they cannot bite or sting and they do not attack the house structure or contents.  They do not breed and reproduce indoors or cause harm.  Though this lessens need for concern, we still hate them! 
Accidental invaders enter structures in late fall and "hibernate" until spring.  When they become active they come into the living space while looking for their way back outside.  They are frequently found around windows and lights because they are attracted to light.  The good news is they will not survive long.  The bad news is that there may be a lot of them.
Here are the most commonly-encountered insects in homes as the weather warms in the spring.  See the photos below and the links to additional details.
Flies (various species).  Flies in homes emerging from colder areas where they have overwintered tend to be sluggish and will fly from windows to lights noisily banging into both.  House flies (Musca domestica), cluster flies (Pollenia rudis) and others are common.  Different flies breed and reproduce in different areas, but it is difficult to breed these flies in the home.  It can be done with accumulations of decaying organic matter, but that has a rather obvious solution, doesn't it!
Multicolored Asian lady beetles.  Adults become active on warm days in the spring.  They are the same adults that moved into the home the previous fall; they do not breed in homes. 
Conifer seed bug This accidental invader does not usually occur in large numbers.  It bears a resemblance to kissing bugs (which are not found in Iowa) but these insects feed on pine seeds and are harmless to humans.  
Brown marmorated stink bug.  This half-inch long invasive insect is still uncommon in Iowa with reports from only 12 Iowa counties (click here for current map).  If you see an insect that appears to be BMSB please send a picture and location information to

Photo of a brown marmorated stink bug
Brown marmorated stink bug. Note light-colored bands along abdomen and in the antennae.

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on March 25, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.